staticperl/perl/op.c

/*    op.c
 *
 *    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
 *    2000, 2001, 2002, 2003, 2004, 2005, by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 * "You see: Mr. Drogo, he married poor Miss Primula Brandybuck.  She was
 * our Mr. Bilbo's first cousin on the mother's side (her mother being the
 * youngest of the Old Took's daughters); and Mr. Drogo was his second
 * cousin.  So Mr. Frodo is his first *and* second cousin, once removed
 * either way, as the saying is, if you follow me."  --the Gaffer
 */

/* This file contains the functions that create, manipulate and optimize
 * the OP structures that hold a compiled perl program.
 *
 * A Perl program is compiled into a tree of OPs. Each op contains
 * structural pointers (eg to its siblings and the next op in the
 * execution sequence), a pointer to the function that would execute the
 * op, plus any data specific to that op. For example, an OP_CONST op
 * points to the pp_const() function and to an SV containing the constant
 * value. When pp_const() is executed, its job is to push that SV onto the
 * stack.
 *
 * OPs are mainly created by the newFOO() functions, which are mainly
 * called from the parser (in perly.y) as the code is parsed. For example
 * the Perl code $a + $b * $c would cause the equivalent of the following
 * to be called (oversimplifying a bit):
 *
 *  newBINOP(OP_ADD, flags,
 *      newSVREF($a),
 *      newBINOP(OP_MULTIPLY, flags, newSVREF($b), newSVREF($c))
 *  )
 *
 * Note that during the build of miniperl, a temporary copy of this file
 * is made, called opmini.c.
 */

/*
Perl's compiler is essentially a 3-pass compiler with interleaved phases:

    A bottom-up pass
    A top-down pass
    An execution-order pass

The bottom-up pass is represented by all the "newOP" routines and
the ck_ routines.  The bottom-upness is actually driven by yacc.
So at the point that a ck_ routine fires, we have no idea what the
context is, either upward in the syntax tree, or either forward or
backward in the execution order.  (The bottom-up parser builds that
part of the execution order it knows about, but if you follow the "next"
links around, you'll find it's actually a closed loop through the
top level node.

Whenever the bottom-up parser gets to a node that supplies context to
its components, it invokes that portion of the top-down pass that applies
to that part of the subtree (and marks the top node as processed, so
if a node further up supplies context, it doesn't have to take the
plunge again).  As a particular subcase of this, as the new node is
built, it takes all the closed execution loops of its subcomponents
and links them into a new closed loop for the higher level node.  But
it's still not the real execution order.

The actual execution order is not known till we get a grammar reduction
to a top-level unit like a subroutine or file that will be called by
"name" rather than via a "next" pointer.  At that point, we can call
into peep() to do that code's portion of the 3rd pass.  It has to be
recursive, but it's recursive on basic blocks, not on tree nodes.
*/

#include "EXTERN.h"
#define PERL_IN_OP_C
#include "perl.h"
#include "keywords.h"

#define CALL_PEEP(o) CALL_FPTR(PL_peepp)(aTHX_ o)

#if defined(PL_OP_SLAB_ALLOC)

#ifndef PERL_SLAB_SIZE
#define PERL_SLAB_SIZE 2048
#endif

void *
Perl_Slab_Alloc(pTHX_ int m, size_t sz)
{
    /*
     * To make incrementing use count easy PL_OpSlab is an I32 *
     * To make inserting the link to slab PL_OpPtr is I32 **
     * So compute size in units of sizeof(I32 *) as that is how Pl_OpPtr increments
     * Add an overhead for pointer to slab and round up as a number of pointers
     */
    sz = (sz + 2*sizeof(I32 *) -1)/sizeof(I32 *);
    if ((PL_OpSpace -= sz) < 0) {
        PL_OpPtr = (I32 **) PerlMemShared_malloc(PERL_SLAB_SIZE*sizeof(I32*)); 
        if (!PL_OpPtr) {
            return NULL;
        }
        Zero(PL_OpPtr,PERL_SLAB_SIZE,I32 **);
        /* We reserve the 0'th I32 sized chunk as a use count */
        PL_OpSlab = (I32 *) PL_OpPtr;
        /* Reduce size by the use count word, and by the size we need.
         * Latter is to mimic the '-=' in the if() above
         */
        PL_OpSpace = PERL_SLAB_SIZE - (sizeof(I32)+sizeof(I32 **)-1)/sizeof(I32 **) - sz;
        /* Allocation pointer starts at the top.
           Theory: because we build leaves before trunk allocating at end
           means that at run time access is cache friendly upward
         */
        PL_OpPtr += PERL_SLAB_SIZE;
    }
    assert( PL_OpSpace >= 0 );
    /* Move the allocation pointer down */
    PL_OpPtr   -= sz;
    assert( PL_OpPtr > (I32 **) PL_OpSlab );
    *PL_OpPtr   = PL_OpSlab;    /* Note which slab it belongs to */
    (*PL_OpSlab)++;             /* Increment use count of slab */
    assert( PL_OpPtr+sz <= ((I32 **) PL_OpSlab + PERL_SLAB_SIZE) );
    assert( *PL_OpSlab > 0 );
    return (void *)(PL_OpPtr + 1);
}

void
Perl_Slab_Free(pTHX_ void *op)
{
    I32 **ptr = (I32 **) op;
    I32 *slab = ptr[-1];
    assert( ptr-1 > (I32 **) slab );
    assert( ptr < ( (I32 **) slab + PERL_SLAB_SIZE) );
    assert( *slab > 0 );
    if (--(*slab) == 0) {
#  ifdef NETWARE
#    define PerlMemShared PerlMem
#  endif
        
    PerlMemShared_free(slab);
        if (slab == PL_OpSlab) {
            PL_OpSpace = 0;
        }
    }
}
#endif
/*
 * In the following definition, the ", Nullop" is just to make the compiler
 * think the expression is of the right type: croak actually does a Siglongjmp.
 */
#define CHECKOP(type,o) \
    ((PL_op_mask && PL_op_mask[type])                                   \
     ? ( op_free((OP*)o),                                       \
         Perl_croak(aTHX_ "'%s' trapped by operation mask", PL_op_desc[type]),  \
         Nullop )                                               \
     : CALL_FPTR(PL_check[type])(aTHX_ (OP*)o))

#define RETURN_UNLIMITED_NUMBER (PERL_INT_MAX / 2)

STATIC char*
S_gv_ename(pTHX_ GV *gv)
{
    STRLEN n_a;
    SV* tmpsv = sv_newmortal();
    gv_efullname3(tmpsv, gv, Nullch);
    return SvPV(tmpsv,n_a);
}

STATIC OP *
S_no_fh_allowed(pTHX_ OP *o)
{
    yyerror(Perl_form(aTHX_ "Missing comma after first argument to %s function",
                 OP_DESC(o)));
    return o;
}

STATIC OP *
S_too_few_arguments(pTHX_ OP *o, char *name)
{
    yyerror(Perl_form(aTHX_ "Not enough arguments for %s", name));
    return o;
}

STATIC OP *
S_too_many_arguments(pTHX_ OP *o, char *name)
{
    yyerror(Perl_form(aTHX_ "Too many arguments for %s", name));
    return o;
}

STATIC void
S_bad_type(pTHX_ I32 n, char *t, char *name, OP *kid)
{
    yyerror(Perl_form(aTHX_ "Type of arg %d to %s must be %s (not %s)",
                 (int)n, name, t, OP_DESC(kid)));
}

STATIC void
S_no_bareword_allowed(pTHX_ OP *o)
{
    qerror(Perl_mess(aTHX_
                     "Bareword \"%"SVf"\" not allowed while \"strict subs\" in use",
                     cSVOPo_sv));
}

/* "register" allocation */

PADOFFSET
Perl_allocmy(pTHX_ char *name)
{
    PADOFFSET off;

    /* complain about "my $_" etc etc */
    if (!(PL_in_my == KEY_our ||
          isALPHA(name[1]) ||
          (USE_UTF8_IN_NAMES && UTF8_IS_START(name[1])) ||
          (name[1] == '_' && (int)strlen(name) > 2)))
    {
        if (!isPRINT(name[1]) || strchr("\t\n\r\f", name[1])) {
            /* 1999-02-27 mjd@plover.com */
            char *p;
            p = strchr(name, '\0');
            /* The next block assumes the buffer is at least 205 chars
               long.  At present, it's always at least 256 chars. */
            if (p-name > 200) {
                strcpy(name+200, "...");
                p = name+199;
            }
            else {
                p[1] = '\0';
            }
            /* Move everything else down one character */
            for (; p-name > 2; p--)
                *p = *(p-1);
            name[2] = toCTRL(name[1]);
            name[1] = '^';
        }
        yyerror(Perl_form(aTHX_ "Can't use global %s in \"my\"",name));
    }
    /* check for duplicate declaration */
    pad_check_dup(name,
                (bool)(PL_in_my == KEY_our),
                (PL_curstash ? PL_curstash : PL_defstash)
    );

    if (PL_in_my_stash && *name != '$') {
        yyerror(Perl_form(aTHX_
                    "Can't declare class for non-scalar %s in \"%s\"",
                     name, PL_in_my == KEY_our ? "our" : "my"));
    }

    /* allocate a spare slot and store the name in that slot */

    off = pad_add_name(name,
                    PL_in_my_stash,
                    (PL_in_my == KEY_our 
                        ? (PL_curstash ? PL_curstash : PL_defstash)
                        : Nullhv
                    ),
                    0 /*  not fake */
    );
    return off;
}


#ifdef USE_5005THREADS
/* find_threadsv is not reentrant */
PADOFFSET
Perl_find_threadsv(pTHX_ const char *name)
{
    char *p;
    PADOFFSET key;
    SV **svp;
    /* We currently only handle names of a single character */
    p = strchr(PL_threadsv_names, *name);
    if (!p)
        return NOT_IN_PAD;
    key = p - PL_threadsv_names;
    MUTEX_LOCK(&thr->mutex);
    svp = av_fetch(thr->threadsv, key, FALSE);
    if (svp)
        MUTEX_UNLOCK(&thr->mutex);
    else {
        SV *sv = NEWSV(0, 0);
        av_store(thr->threadsv, key, sv);
        thr->threadsvp = AvARRAY(thr->threadsv);
        MUTEX_UNLOCK(&thr->mutex);
        /*
         * Some magic variables used to be automagically initialised
         * in gv_fetchpv. Those which are now per-thread magicals get
         * initialised here instead.
         */
        switch (*name) {
        case '_':
            break;
        case ';':
            sv_setpv(sv, "\034");
            sv_magic(sv, 0, PERL_MAGIC_sv, name, 1);
            break;
        case '&':
        case '`':
        case '\'':
            PL_sawampersand = TRUE;
            /* FALL THROUGH */
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            SvREADONLY_on(sv);
            /* FALL THROUGH */

        /* XXX %! tied to Errno.pm needs to be added here.
         * See gv_fetchpv(). */
        /* case '!': */

        default:
            sv_magic(sv, 0, PERL_MAGIC_sv, name, 1);
        }
        DEBUG_S(PerlIO_printf(Perl_error_log,
                              "find_threadsv: new SV %p for $%s%c\n",
                              sv, (*name < 32) ? "^" : "",
                              (*name < 32) ? toCTRL(*name) : *name));
    }
    return key;
}
#endif /* USE_5005THREADS */

/* Destructor */

void
Perl_op_free(pTHX_ OP *o)
{
    register OP *kid, *nextkid;
    OPCODE type;
    PADOFFSET refcnt;

    if (!o || o->op_seq == (U16)-1)
        return;

    if (o->op_private & OPpREFCOUNTED) {
        switch (o->op_type) {
        case OP_LEAVESUB:
        case OP_LEAVESUBLV:
        case OP_LEAVEEVAL:
        case OP_LEAVE:
        case OP_SCOPE:
        case OP_LEAVEWRITE:
            OP_REFCNT_LOCK;
            refcnt = OpREFCNT_dec(o);
            OP_REFCNT_UNLOCK;
            if (refcnt)
                return;
            break;
        default:
            break;
        }
    }

    if (o->op_flags & OPf_KIDS) {
        for (kid = cUNOPo->op_first; kid; kid = nextkid) {
            nextkid = kid->op_sibling; /* Get before next freeing kid */
            op_free(kid);
        }
    }
    type = o->op_type;
    if (type == OP_NULL)
        type = (OPCODE)o->op_targ;

    /* COP* is not cleared by op_clear() so that we may track line
     * numbers etc even after null() */
    if (type == OP_NEXTSTATE || type == OP_SETSTATE || type == OP_DBSTATE)
        cop_free((COP*)o);

    op_clear(o);
    FreeOp(o);
}

void
Perl_op_clear(pTHX_ OP *o)
{

    switch (o->op_type) {
    case OP_NULL:       /* Was holding old type, if any. */
    case OP_ENTEREVAL:  /* Was holding hints. */
#ifdef USE_5005THREADS
    case OP_THREADSV:   /* Was holding index into thr->threadsv AV. */
#endif
        o->op_targ = 0;
        break;
#ifdef USE_5005THREADS
    case OP_ENTERITER:
        if (!(o->op_flags & OPf_SPECIAL))
            break;
        /* FALL THROUGH */
#endif /* USE_5005THREADS */
    default:
        if (!(o->op_flags & OPf_REF)
            || (PL_check[o->op_type] != MEMBER_TO_FPTR(Perl_ck_ftst)))
            break;
        /* FALL THROUGH */
    case OP_GVSV:
    case OP_GV:
    case OP_AELEMFAST:
        if (! (o->op_type == OP_AELEMFAST && o->op_flags & OPf_SPECIAL)) {
            /* not an OP_PADAV replacement */
#ifdef USE_ITHREADS
            if (cPADOPo->op_padix > 0) {
                /* No GvIN_PAD_off(cGVOPo_gv) here, because other references
                 * may still exist on the pad */
                pad_swipe(cPADOPo->op_padix, TRUE);
                cPADOPo->op_padix = 0;
            }
#else
            SvREFCNT_dec(cSVOPo->op_sv);
            cSVOPo->op_sv = Nullsv;
#endif
        }
        break;
    case OP_METHOD_NAMED:
    case OP_CONST:
        SvREFCNT_dec(cSVOPo->op_sv);
        cSVOPo->op_sv = Nullsv;
#ifdef USE_ITHREADS
        /** Bug #15654
          Even if op_clear does a pad_free for the target of the op,
          pad_free doesn't actually remove the sv that exists in the pad;
          instead it lives on. This results in that it could be reused as 
          a target later on when the pad was reallocated.
        **/
        if(o->op_targ) {
          pad_swipe(o->op_targ,1);
          o->op_targ = 0;
        }
#endif
        break;
    case OP_GOTO:
    case OP_NEXT:
    case OP_LAST:
    case OP_REDO:
        if (o->op_flags & (OPf_SPECIAL|OPf_STACKED|OPf_KIDS))
            break;
        /* FALL THROUGH */
    case OP_TRANS:
        if (o->op_private & (OPpTRANS_FROM_UTF|OPpTRANS_TO_UTF)) {
            SvREFCNT_dec(cSVOPo->op_sv);
            cSVOPo->op_sv = Nullsv;
        }
        else {
            Safefree(cPVOPo->op_pv);
            cPVOPo->op_pv = Nullch;
        }
        break;
    case OP_SUBST:
        op_free(cPMOPo->op_pmreplroot);
        goto clear_pmop;
    case OP_PUSHRE:
#ifdef USE_ITHREADS
        if (INT2PTR(PADOFFSET, cPMOPo->op_pmreplroot)) {
            /* No GvIN_PAD_off here, because other references may still
             * exist on the pad */
            pad_swipe(INT2PTR(PADOFFSET, cPMOPo->op_pmreplroot), TRUE);
        }
#else
        SvREFCNT_dec((SV*)cPMOPo->op_pmreplroot);
#endif
        /* FALL THROUGH */
    case OP_MATCH:
    case OP_QR:
clear_pmop:
        {
            HV *pmstash = PmopSTASH(cPMOPo);
            if (pmstash && SvREFCNT(pmstash)) {
                PMOP *pmop = HvPMROOT(pmstash);
                PMOP *lastpmop = NULL;
                while (pmop) {
                    if (cPMOPo == pmop) {
                        if (lastpmop)
                            lastpmop->op_pmnext = pmop->op_pmnext;
                        else
                            HvPMROOT(pmstash) = pmop->op_pmnext;
                        break;
                    }
                    lastpmop = pmop;
                    pmop = pmop->op_pmnext;
                }
            }
            PmopSTASH_free(cPMOPo);
        }
        cPMOPo->op_pmreplroot = Nullop;
        /* we use the "SAFE" version of the PM_ macros here
         * since sv_clean_all might release some PMOPs
         * after PL_regex_padav has been cleared
         * and the clearing of PL_regex_padav needs to
         * happen before sv_clean_all
         */
        ReREFCNT_dec(PM_GETRE_SAFE(cPMOPo));
        PM_SETRE_SAFE(cPMOPo, (REGEXP*)NULL);
#ifdef USE_ITHREADS
        if(PL_regex_pad) {        /* We could be in destruction */
            av_push((AV*) PL_regex_pad[0],(SV*) PL_regex_pad[(cPMOPo)->op_pmoffset]);
            SvREPADTMP_on(PL_regex_pad[(cPMOPo)->op_pmoffset]);
            PM_SETRE(cPMOPo, (cPMOPo)->op_pmoffset);
        }
#endif

        break;
    }

    if (o->op_targ > 0) {
        pad_free(o->op_targ);
        o->op_targ = 0;
    }
}

STATIC void
S_cop_free(pTHX_ COP* cop)
{
    Safefree(cop->cop_label);   /* FIXME: treaddead ??? */
    CopFILE_free(cop);
    CopSTASH_free(cop);
    if (! specialWARN(cop->cop_warnings))
        SvREFCNT_dec(cop->cop_warnings);
    if (! specialCopIO(cop->cop_io)) {
#ifdef USE_ITHREADS
#if 0
        STRLEN len;
        char *s = SvPV(cop->cop_io,len);
        Perl_warn(aTHX_ "io='%.*s'",(int) len,s); /* ??? --jhi */
#endif
#else
        SvREFCNT_dec(cop->cop_io);
#endif
    }
}

void
Perl_op_null(pTHX_ OP *o)
{
    if (o->op_type == OP_NULL)
        return;
    op_clear(o);
    o->op_targ = o->op_type;
    o->op_type = OP_NULL;
    o->op_ppaddr = PL_ppaddr[OP_NULL];
}

void
Perl_op_refcnt_lock(pTHX)
{
    OP_REFCNT_LOCK;
}

void
Perl_op_refcnt_unlock(pTHX)
{
    OP_REFCNT_UNLOCK;
}

/* Contextualizers */

#define LINKLIST(o) ((o)->op_next ? (o)->op_next : linklist((OP*)o))

OP *
Perl_linklist(pTHX_ OP *o)
{
    register OP *kid;

    if (o->op_next)
        return o->op_next;

    /* establish postfix order */
    if (cUNOPo->op_first) {
        o->op_next = LINKLIST(cUNOPo->op_first);
        for (kid = cUNOPo->op_first; kid; kid = kid->op_sibling) {
            if (kid->op_sibling)
                kid->op_next = LINKLIST(kid->op_sibling);
            else
                kid->op_next = o;
        }
    }
    else
        o->op_next = o;

    return o->op_next;
}

OP *
Perl_scalarkids(pTHX_ OP *o)
{
    OP *kid;
    if (o && o->op_flags & OPf_KIDS) {
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            scalar(kid);
    }
    return o;
}

STATIC OP *
S_scalarboolean(pTHX_ OP *o)
{
    if (o->op_type == OP_SASSIGN && cBINOPo->op_first->op_type == OP_CONST) {
        if (ckWARN(WARN_SYNTAX)) {
            line_t oldline = CopLINE(PL_curcop);

            if (PL_copline != NOLINE)
                CopLINE_set(PL_curcop, PL_copline);
            Perl_warner(aTHX_ packWARN(WARN_SYNTAX), "Found = in conditional, should be ==");
            CopLINE_set(PL_curcop, oldline);
        }
    }
    return scalar(o);
}

OP *
Perl_scalar(pTHX_ OP *o)
{
    OP *kid;

    /* assumes no premature commitment */
    if (!o || (o->op_flags & OPf_WANT) || PL_error_count
         || o->op_type == OP_RETURN)
    {
        return o;
    }

    o->op_flags = (o->op_flags & ~OPf_WANT) | OPf_WANT_SCALAR;

    switch (o->op_type) {
    case OP_REPEAT:
        scalar(cBINOPo->op_first);
        break;
    case OP_OR:
    case OP_AND:
    case OP_COND_EXPR:
        for (kid = cUNOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            scalar(kid);
        break;
    case OP_SPLIT:
        if ((kid = cLISTOPo->op_first) && kid->op_type == OP_PUSHRE) {
            if (!kPMOP->op_pmreplroot)
                deprecate_old("implicit split to @_");
        }
        /* FALL THROUGH */
    case OP_MATCH:
    case OP_QR:
    case OP_SUBST:
    case OP_NULL:
    default:
        if (o->op_flags & OPf_KIDS) {
            for (kid = cUNOPo->op_first; kid; kid = kid->op_sibling)
                scalar(kid);
        }
        break;
    case OP_LEAVE:
    case OP_LEAVETRY:
        kid = cLISTOPo->op_first;
        scalar(kid);
        while ((kid = kid->op_sibling)) {
            if (kid->op_sibling)
                scalarvoid(kid);
            else
                scalar(kid);
        }
        WITH_THR(PL_curcop = &PL_compiling);
        break;
    case OP_SCOPE:
    case OP_LINESEQ:
    case OP_LIST:
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling) {
            if (kid->op_sibling)
                scalarvoid(kid);
            else
                scalar(kid);
        }
        WITH_THR(PL_curcop = &PL_compiling);
        break;
    case OP_SORT:
        if (ckWARN(WARN_VOID))
            Perl_warner(aTHX_ packWARN(WARN_VOID), "Useless use of sort in scalar context");
    }
    return o;
}

OP *
Perl_scalarvoid(pTHX_ OP *o)
{
    OP *kid;
    char* useless = 0;
    SV* sv;
    U8 want;

    if (o->op_type == OP_NEXTSTATE
        || o->op_type == OP_SETSTATE
        || o->op_type == OP_DBSTATE
        || (o->op_type == OP_NULL && (o->op_targ == OP_NEXTSTATE
                                      || o->op_targ == OP_SETSTATE
                                      || o->op_targ == OP_DBSTATE)))
        PL_curcop = (COP*)o;            /* for warning below */

    /* assumes no premature commitment */
    want = o->op_flags & OPf_WANT;
    if ((want && want != OPf_WANT_SCALAR) || PL_error_count
         || o->op_type == OP_RETURN)
    {
        return o;
    }

    if ((o->op_private & OPpTARGET_MY)
        && (PL_opargs[o->op_type] & OA_TARGLEX))/* OPp share the meaning */
    {
        return scalar(o);                       /* As if inside SASSIGN */
    }

    o->op_flags = (o->op_flags & ~OPf_WANT) | OPf_WANT_VOID;

    switch (o->op_type) {
    default:
        if (!(PL_opargs[o->op_type] & OA_FOLDCONST))
            break;
        /* FALL THROUGH */
    case OP_REPEAT:
        if (o->op_flags & OPf_STACKED)
            break;
        goto func_ops;
    case OP_SUBSTR:
        if (o->op_private == 4)
            break;
        /* FALL THROUGH */
    case OP_GVSV:
    case OP_WANTARRAY:
    case OP_GV:
    case OP_PADSV:
    case OP_PADAV:
    case OP_PADHV:
    case OP_PADANY:
    case OP_AV2ARYLEN:
    case OP_REF:
    case OP_REFGEN:
    case OP_SREFGEN:
    case OP_DEFINED:
    case OP_HEX:
    case OP_OCT:
    case OP_LENGTH:
    case OP_VEC:
    case OP_INDEX:
    case OP_RINDEX:
    case OP_SPRINTF:
    case OP_AELEM:
    case OP_AELEMFAST:
    case OP_ASLICE:
    case OP_HELEM:
    case OP_HSLICE:
    case OP_UNPACK:
    case OP_PACK:
    case OP_JOIN:
    case OP_LSLICE:
    case OP_ANONLIST:
    case OP_ANONHASH:
    case OP_SORT:
    case OP_REVERSE:
    case OP_RANGE:
    case OP_FLIP:
    case OP_FLOP:
    case OP_CALLER:
    case OP_FILENO:
    case OP_EOF:
    case OP_TELL:
    case OP_GETSOCKNAME:
    case OP_GETPEERNAME:
    case OP_READLINK:
    case OP_TELLDIR:
    case OP_GETPPID:
    case OP_GETPGRP:
    case OP_GETPRIORITY:
    case OP_TIME:
    case OP_TMS:
    case OP_LOCALTIME:
    case OP_GMTIME:
    case OP_GHBYNAME:
    case OP_GHBYADDR:
    case OP_GHOSTENT:
    case OP_GNBYNAME:
    case OP_GNBYADDR:
    case OP_GNETENT:
    case OP_GPBYNAME:
    case OP_GPBYNUMBER:
    case OP_GPROTOENT:
    case OP_GSBYNAME:
    case OP_GSBYPORT:
    case OP_GSERVENT:
    case OP_GPWNAM:
    case OP_GPWUID:
    case OP_GGRNAM:
    case OP_GGRGID:
    case OP_GETLOGIN:
    case OP_PROTOTYPE:
      func_ops:
        if (!(o->op_private & (OPpLVAL_INTRO|OPpOUR_INTRO)))
            useless = OP_DESC(o);
        break;

    case OP_RV2GV:
    case OP_RV2SV:
    case OP_RV2AV:
    case OP_RV2HV:
        if (!(o->op_private & (OPpLVAL_INTRO|OPpOUR_INTRO)) &&
                (!o->op_sibling || o->op_sibling->op_type != OP_READLINE))
            useless = "a variable";
        break;

    case OP_CONST:
        sv = cSVOPo_sv;
        if (cSVOPo->op_private & OPpCONST_STRICT)
            no_bareword_allowed(o);
        else {
            if (ckWARN(WARN_VOID)) {
                useless = "a constant";
                /* don't warn on optimised away booleans, eg 
                 * use constant Foo, 5; Foo || print; */
                if (cSVOPo->op_private & OPpCONST_SHORTCIRCUIT)
                    useless = 0;
                /* the constants 0 and 1 are permitted as they are
                   conventionally used as dummies in constructs like
                        1 while some_condition_with_side_effects;  */
                else if (SvNIOK(sv) && (SvNV(sv) == 0.0 || SvNV(sv) == 1.0))
                    useless = 0;
                else if (SvPOK(sv)) {
                  /* perl4's way of mixing documentation and code
                     (before the invention of POD) was based on a
                     trick to mix nroff and perl code. The trick was
                     built upon these three nroff macros being used in
                     void context. The pink camel has the details in
                     the script wrapman near page 319. */
                    if (strnEQ(SvPVX(sv), "di", 2) ||
                        strnEQ(SvPVX(sv), "ds", 2) ||
                        strnEQ(SvPVX(sv), "ig", 2))
                            useless = 0;
                }
            }
        }
        op_null(o);             /* don't execute or even remember it */
        break;

    case OP_POSTINC:
        o->op_type = OP_PREINC;         /* pre-increment is faster */
        o->op_ppaddr = PL_ppaddr[OP_PREINC];
        break;

    case OP_POSTDEC:
        o->op_type = OP_PREDEC;         /* pre-decrement is faster */
        o->op_ppaddr = PL_ppaddr[OP_PREDEC];
        break;

    case OP_OR:
    case OP_AND:
    case OP_COND_EXPR:
        for (kid = cUNOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            scalarvoid(kid);
        break;

    case OP_NULL:
        if (o->op_flags & OPf_STACKED)
            break;
        /* FALL THROUGH */
    case OP_NEXTSTATE:
    case OP_DBSTATE:
    case OP_ENTERTRY:
    case OP_ENTER:
        if (!(o->op_flags & OPf_KIDS))
            break;
        /* FALL THROUGH */
    case OP_SCOPE:
    case OP_LEAVE:
    case OP_LEAVETRY:
    case OP_LEAVELOOP:
    case OP_LINESEQ:
    case OP_LIST:
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            scalarvoid(kid);
        break;
    case OP_ENTEREVAL:
        scalarkids(o);
        break;
    case OP_REQUIRE:
        /* all requires must return a boolean value */
        o->op_flags &= ~OPf_WANT;
        /* FALL THROUGH */
    case OP_SCALAR:
        return scalar(o);
    case OP_SPLIT:
        if ((kid = cLISTOPo->op_first) && kid->op_type == OP_PUSHRE) {
            if (!kPMOP->op_pmreplroot)
                deprecate_old("implicit split to @_");
        }
        break;
    }
    if (useless && ckWARN(WARN_VOID))
        Perl_warner(aTHX_ packWARN(WARN_VOID), "Useless use of %s in void context", useless);
    return o;
}

OP *
Perl_listkids(pTHX_ OP *o)
{
    OP *kid;
    if (o && o->op_flags & OPf_KIDS) {
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            list(kid);
    }
    return o;
}

OP *
Perl_list(pTHX_ OP *o)
{
    OP *kid;

    /* assumes no premature commitment */
    if (!o || (o->op_flags & OPf_WANT) || PL_error_count
         || o->op_type == OP_RETURN)
    {
        return o;
    }

    if ((o->op_private & OPpTARGET_MY)
        && (PL_opargs[o->op_type] & OA_TARGLEX))/* OPp share the meaning */
    {
        return o;                               /* As if inside SASSIGN */
    }

    o->op_flags = (o->op_flags & ~OPf_WANT) | OPf_WANT_LIST;

    switch (o->op_type) {
    case OP_FLOP:
    case OP_REPEAT:
        list(cBINOPo->op_first);
        break;
    case OP_OR:
    case OP_AND:
    case OP_COND_EXPR:
        for (kid = cUNOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            list(kid);
        break;
    default:
    case OP_MATCH:
    case OP_QR:
    case OP_SUBST:
    case OP_NULL:
        if (!(o->op_flags & OPf_KIDS))
            break;
        if (!o->op_next && cUNOPo->op_first->op_type == OP_FLOP) {
            list(cBINOPo->op_first);
            return gen_constant_list(o);
        }
    case OP_LIST:
        listkids(o);
        break;
    case OP_LEAVE:
    case OP_LEAVETRY:
        kid = cLISTOPo->op_first;
        list(kid);
        while ((kid = kid->op_sibling)) {
            if (kid->op_sibling)
                scalarvoid(kid);
            else
                list(kid);
        }
        WITH_THR(PL_curcop = &PL_compiling);
        break;
    case OP_SCOPE:
    case OP_LINESEQ:
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling) {
            if (kid->op_sibling)
                scalarvoid(kid);
            else
                list(kid);
        }
        WITH_THR(PL_curcop = &PL_compiling);
        break;
    case OP_REQUIRE:
        /* all requires must return a boolean value */
        o->op_flags &= ~OPf_WANT;
        return scalar(o);
    }
    return o;
}

OP *
Perl_scalarseq(pTHX_ OP *o)
{
    OP *kid;

    if (o) {
        if (o->op_type == OP_LINESEQ ||
             o->op_type == OP_SCOPE ||
             o->op_type == OP_LEAVE ||
             o->op_type == OP_LEAVETRY)
        {
            for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling) {
                if (kid->op_sibling) {
                    scalarvoid(kid);
                }
            }
            PL_curcop = &PL_compiling;
        }
        o->op_flags &= ~OPf_PARENS;
        if (PL_hints & HINT_BLOCK_SCOPE)
            o->op_flags |= OPf_PARENS;
    }
    else
        o = newOP(OP_STUB, 0);
    return o;
}

STATIC OP *
S_modkids(pTHX_ OP *o, I32 type)
{
    OP *kid;
    if (o && o->op_flags & OPf_KIDS) {
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            mod(kid, type);
    }
    return o;
}

OP *
Perl_mod(pTHX_ OP *o, I32 type)
{
    OP *kid;

    if (!o || PL_error_count)
        return o;

    if ((o->op_private & OPpTARGET_MY)
        && (PL_opargs[o->op_type] & OA_TARGLEX))/* OPp share the meaning */
    {
        return o;
    }

    switch (o->op_type) {
    case OP_UNDEF:
        PL_modcount++;
        return o;
    case OP_CONST:
        if (!(o->op_private & (OPpCONST_ARYBASE)))
            goto nomod;
        if (PL_eval_start && PL_eval_start->op_type == OP_CONST) {
            PL_compiling.cop_arybase = (I32)SvIV(cSVOPx(PL_eval_start)->op_sv);
            PL_eval_start = 0;
        }
        else if (!type) {
            SAVEI32(PL_compiling.cop_arybase);
            PL_compiling.cop_arybase = 0;
        }
        else if (type == OP_REFGEN)
            goto nomod;
        else
            Perl_croak(aTHX_ "That use of $[ is unsupported");
        break;
    case OP_STUB:
        if (o->op_flags & OPf_PARENS)
            break;
        goto nomod;
    case OP_ENTERSUB:
        if ((type == OP_UNDEF || type == OP_REFGEN) &&
            !(o->op_flags & OPf_STACKED)) {
            o->op_type = OP_RV2CV;              /* entersub => rv2cv */
            o->op_ppaddr = PL_ppaddr[OP_RV2CV];
            assert(cUNOPo->op_first->op_type == OP_NULL);
            op_null(((LISTOP*)cUNOPo->op_first)->op_first);/* disable pushmark */
            break;
        }
        else if (o->op_private & OPpENTERSUB_NOMOD)
            return o;
        else {                          /* lvalue subroutine call */
            o->op_private |= OPpLVAL_INTRO;
            PL_modcount = RETURN_UNLIMITED_NUMBER;
            if (type == OP_GREPSTART || type == OP_ENTERSUB || type == OP_REFGEN) {
                /* Backward compatibility mode: */
                o->op_private |= OPpENTERSUB_INARGS;
                break;
            }
            else {                      /* Compile-time error message: */
                OP *kid = cUNOPo->op_first;
                CV *cv;
                OP *okid;

                if (kid->op_type == OP_PUSHMARK)
                    goto skip_kids;
                if (kid->op_type != OP_NULL || kid->op_targ != OP_LIST)
                    Perl_croak(aTHX_
                               "panic: unexpected lvalue entersub "
                               "args: type/targ %ld:%"UVuf,
                               (long)kid->op_type, (UV)kid->op_targ);
                kid = kLISTOP->op_first;
              skip_kids:
                while (kid->op_sibling)
                    kid = kid->op_sibling;
                if (!(kid->op_type == OP_NULL && kid->op_targ == OP_RV2CV)) {
                    /* Indirect call */
                    if (kid->op_type == OP_METHOD_NAMED
                        || kid->op_type == OP_METHOD)
                    {
                        UNOP *newop;

                        NewOp(1101, newop, 1, UNOP);
                        newop->op_type = OP_RV2CV;
                        newop->op_ppaddr = PL_ppaddr[OP_RV2CV];
                        newop->op_first = Nullop;
                        newop->op_next = (OP*)newop;
                        kid->op_sibling = (OP*)newop;
                        newop->op_private |= OPpLVAL_INTRO;
                        break;
                    }

                    if (kid->op_type != OP_RV2CV)
                        Perl_croak(aTHX_
                                   "panic: unexpected lvalue entersub "
                                   "entry via type/targ %ld:%"UVuf,
                                   (long)kid->op_type, (UV)kid->op_targ);
                    kid->op_private |= OPpLVAL_INTRO;
                    break;      /* Postpone until runtime */
                }

                okid = kid;
                kid = kUNOP->op_first;
                if (kid->op_type == OP_NULL && kid->op_targ == OP_RV2SV)
                    kid = kUNOP->op_first;
                if (kid->op_type == OP_NULL)
                    Perl_croak(aTHX_
                               "Unexpected constant lvalue entersub "
                               "entry via type/targ %ld:%"UVuf,
                               (long)kid->op_type, (UV)kid->op_targ);
                if (kid->op_type != OP_GV) {
                    /* Restore RV2CV to check lvalueness */
                  restore_2cv:
                    if (kid->op_next && kid->op_next != kid) { /* Happens? */
                        okid->op_next = kid->op_next;
                        kid->op_next = okid;
                    }
                    else
                        okid->op_next = Nullop;
                    okid->op_type = OP_RV2CV;
                    okid->op_targ = 0;
                    okid->op_ppaddr = PL_ppaddr[OP_RV2CV];
                    okid->op_private |= OPpLVAL_INTRO;
                    break;
                }

                cv = GvCV(kGVOP_gv);
                if (!cv)
                    goto restore_2cv;
                if (CvLVALUE(cv))
                    break;
            }
        }
        /* FALL THROUGH */
    default:
      nomod:
        /* grep, foreach, subcalls, refgen */
        if (type == OP_GREPSTART || type == OP_ENTERSUB || type == OP_REFGEN)
            break;
        yyerror(Perl_form(aTHX_ "Can't modify %s in %s",
                     (o->op_type == OP_NULL && (o->op_flags & OPf_SPECIAL)
                      ? "do block"
                      : (o->op_type == OP_ENTERSUB
                        ? "non-lvalue subroutine call"
                        : OP_DESC(o))),
                     type ? PL_op_desc[type] : "local"));
        return o;

    case OP_PREINC:
    case OP_PREDEC:
    case OP_POW:
    case OP_MULTIPLY:
    case OP_DIVIDE:
    case OP_MODULO:
    case OP_REPEAT:
    case OP_ADD:
    case OP_SUBTRACT:
    case OP_CONCAT:
    case OP_LEFT_SHIFT:
    case OP_RIGHT_SHIFT:
    case OP_BIT_AND:
    case OP_BIT_XOR:
    case OP_BIT_OR:
    case OP_I_MULTIPLY:
    case OP_I_DIVIDE:
    case OP_I_MODULO:
    case OP_I_ADD:
    case OP_I_SUBTRACT:
        if (!(o->op_flags & OPf_STACKED))
            goto nomod;
        PL_modcount++;
        break;

    case OP_COND_EXPR:
        for (kid = cUNOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            mod(kid, type);
        break;

    case OP_RV2AV:
    case OP_RV2HV:
        if (type == OP_REFGEN && o->op_flags & OPf_PARENS) {
           PL_modcount = RETURN_UNLIMITED_NUMBER;
            return o;           /* Treat \(@foo) like ordinary list. */
        }
        /* FALL THROUGH */
    case OP_RV2GV:
        if (scalar_mod_type(o, type))
            goto nomod;
        ref(cUNOPo->op_first, o->op_type);
        /* FALL THROUGH */
    case OP_ASLICE:
    case OP_HSLICE:
        if (type == OP_LEAVESUBLV)
            o->op_private |= OPpMAYBE_LVSUB;
        /* FALL THROUGH */
    case OP_AASSIGN:
    case OP_NEXTSTATE:
    case OP_DBSTATE:
       PL_modcount = RETURN_UNLIMITED_NUMBER;
        break;
    case OP_RV2SV:
        ref(cUNOPo->op_first, o->op_type);
        /* FALL THROUGH */
    case OP_GV:
    case OP_AV2ARYLEN:
        PL_hints |= HINT_BLOCK_SCOPE;
    case OP_SASSIGN:
    case OP_ANDASSIGN:
    case OP_ORASSIGN:
    case OP_AELEMFAST:
        /* Needed if maint gets patch 19588
           localize = -1;
        */
        PL_modcount++;
        break;

    case OP_PADAV:
    case OP_PADHV:
       PL_modcount = RETURN_UNLIMITED_NUMBER;
        if (type == OP_REFGEN && o->op_flags & OPf_PARENS)
            return o;           /* Treat \(@foo) like ordinary list. */
        if (scalar_mod_type(o, type))
            goto nomod;
        if (type == OP_LEAVESUBLV)
            o->op_private |= OPpMAYBE_LVSUB;
        /* FALL THROUGH */
    case OP_PADSV:
        PL_modcount++;
        if (!type)
        {   /* XXX DAPM 2002.08.25 tmp assert test */
            /* XXX */ assert(av_fetch(PL_comppad_name, (o->op_targ), FALSE));
            /* XXX */ assert(*av_fetch(PL_comppad_name, (o->op_targ), FALSE));

            Perl_croak(aTHX_ "Can't localize lexical variable %s",
                 PAD_COMPNAME_PV(o->op_targ));
        }
        break;

#ifdef USE_5005THREADS
    case OP_THREADSV:
        PL_modcount++;  /* XXX ??? */
        break;
#endif /* USE_5005THREADS */

    case OP_PUSHMARK:
        break;

    case OP_KEYS:
        if (type != OP_SASSIGN)
            goto nomod;
        goto lvalue_func;
    case OP_SUBSTR:
        if (o->op_private == 4) /* don't allow 4 arg substr as lvalue */
            goto nomod;
        /* FALL THROUGH */
    case OP_POS:
    case OP_VEC:
        if (type == OP_LEAVESUBLV)
            o->op_private |= OPpMAYBE_LVSUB;
      lvalue_func:
        pad_free(o->op_targ);
        o->op_targ = pad_alloc(o->op_type, SVs_PADMY);
        assert(SvTYPE(PAD_SV(o->op_targ)) == SVt_NULL);
        if (o->op_flags & OPf_KIDS)
            mod(cBINOPo->op_first->op_sibling, type);
        break;

    case OP_AELEM:
    case OP_HELEM:
        ref(cBINOPo->op_first, o->op_type);
        if (type == OP_ENTERSUB &&
             !(o->op_private & (OPpLVAL_INTRO | OPpDEREF)))
            o->op_private |= OPpLVAL_DEFER;
        if (type == OP_LEAVESUBLV)
            o->op_private |= OPpMAYBE_LVSUB;
        PL_modcount++;
        break;

    case OP_SCOPE:
    case OP_LEAVE:
    case OP_ENTER:
    case OP_LINESEQ:
        if (o->op_flags & OPf_KIDS)
            mod(cLISTOPo->op_last, type);
        break;

    case OP_NULL:
        if (o->op_flags & OPf_SPECIAL)          /* do BLOCK */
            goto nomod;
        else if (!(o->op_flags & OPf_KIDS))
            break;
        if (o->op_targ != OP_LIST) {
            mod(cBINOPo->op_first, type);
            break;
        }
        /* FALL THROUGH */
    case OP_LIST:
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            mod(kid, type);
        break;

    case OP_RETURN:
        if (type != OP_LEAVESUBLV)
            goto nomod;
        break; /* mod()ing was handled by ck_return() */
    }

    /* [20011101.069] File test operators interpret OPf_REF to mean that
       their argument is a filehandle; thus \stat(".") should not set
       it. AMS 20011102 */
    if (type == OP_REFGEN &&
        PL_check[o->op_type] == MEMBER_TO_FPTR(Perl_ck_ftst))
        return o;

    if (type != OP_LEAVESUBLV)
        o->op_flags |= OPf_MOD;

    if (type == OP_AASSIGN || type == OP_SASSIGN)
        o->op_flags |= OPf_SPECIAL|OPf_REF;
    else if (!type) {
        o->op_private |= OPpLVAL_INTRO;
        o->op_flags &= ~OPf_SPECIAL;
        PL_hints |= HINT_BLOCK_SCOPE;
    }
    else if (type != OP_GREPSTART && type != OP_ENTERSUB
             && type != OP_LEAVESUBLV)
        o->op_flags |= OPf_REF;
    return o;
}

STATIC bool
S_scalar_mod_type(pTHX_ OP *o, I32 type)
{
    switch (type) {
    case OP_SASSIGN:
        if (o->op_type == OP_RV2GV)
            return FALSE;
        /* FALL THROUGH */
    case OP_PREINC:
    case OP_PREDEC:
    case OP_POSTINC:
    case OP_POSTDEC:
    case OP_I_PREINC:
    case OP_I_PREDEC:
    case OP_I_POSTINC:
    case OP_I_POSTDEC:
    case OP_POW:
    case OP_MULTIPLY:
    case OP_DIVIDE:
    case OP_MODULO:
    case OP_REPEAT:
    case OP_ADD:
    case OP_SUBTRACT:
    case OP_I_MULTIPLY:
    case OP_I_DIVIDE:
    case OP_I_MODULO:
    case OP_I_ADD:
    case OP_I_SUBTRACT:
    case OP_LEFT_SHIFT:
    case OP_RIGHT_SHIFT:
    case OP_BIT_AND:
    case OP_BIT_XOR:
    case OP_BIT_OR:
    case OP_CONCAT:
    case OP_SUBST:
    case OP_TRANS:
    case OP_READ:
    case OP_SYSREAD:
    case OP_RECV:
    case OP_ANDASSIGN:
    case OP_ORASSIGN:
        return TRUE;
    default:
        return FALSE;
    }
}

STATIC bool
S_is_handle_constructor(pTHX_ OP *o, I32 argnum)
{
    switch (o->op_type) {
    case OP_PIPE_OP:
    case OP_SOCKPAIR:
        if (argnum == 2)
            return TRUE;
        /* FALL THROUGH */
    case OP_SYSOPEN:
    case OP_OPEN:
    case OP_SELECT:             /* XXX c.f. SelectSaver.pm */
    case OP_SOCKET:
    case OP_OPEN_DIR:
    case OP_ACCEPT:
        if (argnum == 1)
            return TRUE;
        /* FALL THROUGH */
    default:
        return FALSE;
    }
}

OP *
Perl_refkids(pTHX_ OP *o, I32 type)
{
    OP *kid;
    if (o && o->op_flags & OPf_KIDS) {
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            ref(kid, type);
    }
    return o;
}

OP *
Perl_ref(pTHX_ OP *o, I32 type)
{
    OP *kid;

    if (!o || PL_error_count)
        return o;

    switch (o->op_type) {
    case OP_ENTERSUB:
        if ((type == OP_EXISTS || type == OP_DEFINED || type == OP_LOCK) &&
            !(o->op_flags & OPf_STACKED)) {
            o->op_type = OP_RV2CV;             /* entersub => rv2cv */
            o->op_ppaddr = PL_ppaddr[OP_RV2CV];
            assert(cUNOPo->op_first->op_type == OP_NULL);
            op_null(((LISTOP*)cUNOPo->op_first)->op_first);     /* disable pushmark */
            o->op_flags |= OPf_SPECIAL;
        }
        break;

    case OP_COND_EXPR:
        for (kid = cUNOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            ref(kid, type);
        break;
    case OP_RV2SV:
        if (type == OP_DEFINED)
            o->op_flags |= OPf_SPECIAL;         /* don't create GV */
        ref(cUNOPo->op_first, o->op_type);
        /* FALL THROUGH */
    case OP_PADSV:
        if (type == OP_RV2SV || type == OP_RV2AV || type == OP_RV2HV) {
            o->op_private |= (type == OP_RV2AV ? OPpDEREF_AV
                              : type == OP_RV2HV ? OPpDEREF_HV
                              : OPpDEREF_SV);
            o->op_flags |= OPf_MOD;
        }
        break;

    case OP_THREADSV:
        o->op_flags |= OPf_MOD;         /* XXX ??? */
        break;

    case OP_RV2AV:
    case OP_RV2HV:
        o->op_flags |= OPf_REF;
        /* FALL THROUGH */
    case OP_RV2GV:
        if (type == OP_DEFINED)
            o->op_flags |= OPf_SPECIAL;         /* don't create GV */
        ref(cUNOPo->op_first, o->op_type);
        break;

    case OP_PADAV:
    case OP_PADHV:
        o->op_flags |= OPf_REF;
        break;

    case OP_SCALAR:
    case OP_NULL:
        if (!(o->op_flags & OPf_KIDS))
            break;
        ref(cBINOPo->op_first, type);
        break;
    case OP_AELEM:
    case OP_HELEM:
        ref(cBINOPo->op_first, o->op_type);
        if (type == OP_RV2SV || type == OP_RV2AV || type == OP_RV2HV) {
            o->op_private |= (type == OP_RV2AV ? OPpDEREF_AV
                              : type == OP_RV2HV ? OPpDEREF_HV
                              : OPpDEREF_SV);
            o->op_flags |= OPf_MOD;
        }
        break;

    case OP_SCOPE:
    case OP_LEAVE:
    case OP_ENTER:
    case OP_LIST:
        if (!(o->op_flags & OPf_KIDS))
            break;
        ref(cLISTOPo->op_last, type);
        break;
    default:
        break;
    }
    return scalar(o);

}

STATIC OP *
S_dup_attrlist(pTHX_ OP *o)
{
    OP *rop = Nullop;

    /* An attrlist is either a simple OP_CONST or an OP_LIST with kids,
     * where the first kid is OP_PUSHMARK and the remaining ones
     * are OP_CONST.  We need to push the OP_CONST values.
     */
    if (o->op_type == OP_CONST)
        rop = newSVOP(OP_CONST, o->op_flags, SvREFCNT_inc(cSVOPo->op_sv));
    else {
        assert((o->op_type == OP_LIST) && (o->op_flags & OPf_KIDS));
        for (o = cLISTOPo->op_first; o; o=o->op_sibling) {
            if (o->op_type == OP_CONST)
                rop = append_elem(OP_LIST, rop,
                                  newSVOP(OP_CONST, o->op_flags,
                                          SvREFCNT_inc(cSVOPo->op_sv)));
        }
    }
    return rop;
}

STATIC void
S_apply_attrs(pTHX_ HV *stash, SV *target, OP *attrs, bool for_my)
{
    SV *stashsv;

    /* fake up C<use attributes $pkg,$rv,@attrs> */
    ENTER;              /* need to protect against side-effects of 'use' */
    SAVEINT(PL_expect);
    if (stash)
        stashsv = newSVpv(HvNAME(stash), 0);
    else
        stashsv = &PL_sv_no;

#define ATTRSMODULE "attributes"
#define ATTRSMODULE_PM "attributes.pm"

    if (for_my) {
        SV **svp;
        /* Don't force the C<use> if we don't need it. */
        svp = hv_fetch(GvHVn(PL_incgv), ATTRSMODULE_PM,
                       sizeof(ATTRSMODULE_PM)-1, 0);
        if (svp && *svp != &PL_sv_undef)
            ;           /* already in %INC */
        else
            Perl_load_module(aTHX_ PERL_LOADMOD_NOIMPORT,
                             newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
                             Nullsv);
    }
    else {
        Perl_load_module(aTHX_ PERL_LOADMOD_IMPORT_OPS,
                         newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
                         Nullsv,
                         prepend_elem(OP_LIST,
                                      newSVOP(OP_CONST, 0, stashsv),
                                      prepend_elem(OP_LIST,
                                                   newSVOP(OP_CONST, 0,
                                                           newRV(target)),
                                                   dup_attrlist(attrs))));
    }
    LEAVE;
}

STATIC void
S_apply_attrs_my(pTHX_ HV *stash, OP *target, OP *attrs, OP **imopsp)
{
    OP *pack, *imop, *arg;
    SV *meth, *stashsv;

    if (!attrs)
        return;

    assert(target->op_type == OP_PADSV ||
           target->op_type == OP_PADHV ||
           target->op_type == OP_PADAV);

    /* Ensure that attributes.pm is loaded. */
    apply_attrs(stash, PAD_SV(target->op_targ), attrs, TRUE);

    /* Need package name for method call. */
    pack = newSVOP(OP_CONST, 0, newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1));

    /* Build up the real arg-list. */
    if (stash)
        stashsv = newSVpv(HvNAME(stash), 0);
    else
        stashsv = &PL_sv_no;
    arg = newOP(OP_PADSV, 0);
    arg->op_targ = target->op_targ;
    arg = prepend_elem(OP_LIST,
                       newSVOP(OP_CONST, 0, stashsv),
                       prepend_elem(OP_LIST,
                                    newUNOP(OP_REFGEN, 0,
                                            mod(arg, OP_REFGEN)),
                                    dup_attrlist(attrs)));

    /* Fake up a method call to import */
    meth = newSVpvn("import", 6);
    (void)SvUPGRADE(meth, SVt_PVIV);
    (void)SvIOK_on(meth);
    PERL_HASH(SvUVX(meth), SvPVX(meth), SvCUR(meth));
    imop = convert(OP_ENTERSUB, OPf_STACKED|OPf_SPECIAL|OPf_WANT_VOID,
                   append_elem(OP_LIST,
                               prepend_elem(OP_LIST, pack, list(arg)),
                               newSVOP(OP_METHOD_NAMED, 0, meth)));
    imop->op_private |= OPpENTERSUB_NOMOD;

    /* Combine the ops. */
    *imopsp = append_elem(OP_LIST, *imopsp, imop);
}

/*
=notfor apidoc apply_attrs_string

Attempts to apply a list of attributes specified by the C<attrstr> and
C<len> arguments to the subroutine identified by the C<cv> argument which
is expected to be associated with the package identified by the C<stashpv>
argument (see L<attributes>).  It gets this wrong, though, in that it
does not correctly identify the boundaries of the individual attribute
specifications within C<attrstr>.  This is not really intended for the
public API, but has to be listed here for systems such as AIX which
need an explicit export list for symbols.  (It's called from XS code
in support of the C<ATTRS:> keyword from F<xsubpp>.)  Patches to fix it
to respect attribute syntax properly would be welcome.

=cut
*/

void
Perl_apply_attrs_string(pTHX_ char *stashpv, CV *cv,
                        char *attrstr, STRLEN len)
{
    OP *attrs = Nullop;

    if (!len) {
        len = strlen(attrstr);
    }

    while (len) {
        for (; isSPACE(*attrstr) && len; --len, ++attrstr) ;
        if (len) {
            char *sstr = attrstr;
            for (; !isSPACE(*attrstr) && len; --len, ++attrstr) ;
            attrs = append_elem(OP_LIST, attrs,
                                newSVOP(OP_CONST, 0,
                                        newSVpvn(sstr, attrstr-sstr)));
        }
    }

    Perl_load_module(aTHX_ PERL_LOADMOD_IMPORT_OPS,
                     newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
                     Nullsv, prepend_elem(OP_LIST,
                                  newSVOP(OP_CONST, 0, newSVpv(stashpv,0)),
                                  prepend_elem(OP_LIST,
                                               newSVOP(OP_CONST, 0,
                                                       newRV((SV*)cv)),
                                               attrs)));
}

STATIC OP *
S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
{
    OP *kid;
    I32 type;

    if (!o || PL_error_count)
        return o;

    type = o->op_type;
    if (type == OP_LIST) {
        for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
            my_kid(kid, attrs, imopsp);
    } else if (type == OP_UNDEF) {
        return o;
    } else if (type == OP_RV2SV ||      /* "our" declaration */
               type == OP_RV2AV ||
               type == OP_RV2HV) { /* XXX does this let anything illegal in? */
        if (cUNOPo->op_first->op_type != OP_GV) { /* MJD 20011224 */
            yyerror(Perl_form(aTHX_ "Can't declare %s in %s",
                        OP_DESC(o), PL_in_my == KEY_our ? "our" : "my"));
        } else if (attrs) {
            GV *gv = cGVOPx_gv(cUNOPo->op_first);
            PL_in_my = FALSE;
            PL_in_my_stash = Nullhv;
            apply_attrs(GvSTASH(gv),
                        (type == OP_RV2SV ? GvSV(gv) :
                         type == OP_RV2AV ? (SV*)GvAV(gv) :
                         type == OP_RV2HV ? (SV*)GvHV(gv) : (SV*)gv),
                        attrs, FALSE);
        }
        o->op_private |= OPpOUR_INTRO;
        return o;
    }
    else if (type != OP_PADSV &&
             type != OP_PADAV &&
             type != OP_PADHV &&
             type != OP_PUSHMARK)
    {
        yyerror(Perl_form(aTHX_ "Can't declare %s in \"%s\"",
                          OP_DESC(o),
                          PL_in_my == KEY_our ? "our" : "my"));
        return o;
    }
    else if (attrs && type != OP_PUSHMARK) {
        HV *stash;

        PL_in_my = FALSE;
        PL_in_my_stash = Nullhv;

        /* check for C<my Dog $spot> when deciding package */
        stash = PAD_COMPNAME_TYPE(o->op_targ);
        if (!stash)
            stash = PL_curstash;
        apply_attrs_my(stash, o, attrs, imopsp);
    }
    o->op_flags |= OPf_MOD;
    o->op_private |= OPpLVAL_INTRO;
    return o;
}

OP *
Perl_my_attrs(pTHX_ OP *o, OP *attrs)
{
    OP *rops = Nullop;
    int maybe_scalar = 0;

/* [perl #17376]: this appears to be premature, and results in code such as
   C< our(%x); > executing in list mode rather than void mode */
#if 0
    if (o->op_flags & OPf_PARENS)
        list(o);
    else
        maybe_scalar = 1;
#else
    maybe_scalar = 1;
#endif
    if (attrs)
        SAVEFREEOP(attrs);
    o = my_kid(o, attrs, &rops);
    if (rops) {
        if (maybe_scalar && o->op_type == OP_PADSV) {
            o = scalar(append_list(OP_LIST, (LISTOP*)rops, (LISTOP*)o));
            o->op_private |= OPpLVAL_INTRO;
        }
        else
            o = append_list(OP_LIST, (LISTOP*)o, (LISTOP*)rops);
    }
    PL_in_my = FALSE;
    PL_in_my_stash = Nullhv;
    return o;
}

OP *
Perl_my(pTHX_ OP *o)
{
    return my_attrs(o, Nullop);
}

OP *
Perl_sawparens(pTHX_ OP *o)
{
    if (o)
        o->op_flags |= OPf_PARENS;
    return o;
}

OP *
Perl_bind_match(pTHX_ I32 type, OP *left, OP *right)
{
    OP *o;

    if (ckWARN(WARN_MISC) &&
      (left->op_type == OP_RV2AV ||
       left->op_type == OP_RV2HV ||
       left->op_type == OP_PADAV ||
       left->op_type == OP_PADHV)) {
      char *desc = PL_op_desc[(right->op_type == OP_SUBST ||
                            right->op_type == OP_TRANS)
                           ? right->op_type : OP_MATCH];
      const char *sample = ((left->op_type == OP_RV2AV ||
                             left->op_type == OP_PADAV)
                            ? "@array" : "%hash");
      Perl_warner(aTHX_ packWARN(WARN_MISC),
             "Applying %s to %s will act on scalar(%s)",
             desc, sample, sample);
    }

    if (right->op_type == OP_CONST &&
        cSVOPx(right)->op_private & OPpCONST_BARE &&
        cSVOPx(right)->op_private & OPpCONST_STRICT)
    {
        no_bareword_allowed(right);
    }

    if (!(right->op_flags & OPf_STACKED) &&
       (right->op_type == OP_MATCH ||
        right->op_type == OP_SUBST ||
        right->op_type == OP_TRANS)) {
        right->op_flags |= OPf_STACKED;
        if (right->op_type != OP_MATCH &&
            ! (right->op_type == OP_TRANS &&
               right->op_private & OPpTRANS_IDENTICAL))
            left = mod(left, right->op_type);
        if (right->op_type == OP_TRANS)
            o = newBINOP(OP_NULL, OPf_STACKED, scalar(left), right);
        else
            o = prepend_elem(right->op_type, scalar(left), right);
        if (type == OP_NOT)
            return newUNOP(OP_NOT, 0, scalar(o));
        return o;
    }
    else
        return bind_match(type, left,
                pmruntime(newPMOP(OP_MATCH, 0), right, Nullop));
}

OP *
Perl_invert(pTHX_ OP *o)
{
    if (!o)
        return o;
    /* XXX need to optimize away NOT NOT here?  Or do we let optimizer do it? */
    return newUNOP(OP_NOT, OPf_SPECIAL, scalar(o));
}

OP *
Perl_scope(pTHX_ OP *o)
{
    if (o) {
        if (o->op_flags & OPf_PARENS || PERLDB_NOOPT || PL_tainting) {
            o = prepend_elem(OP_LINESEQ, newOP(OP_ENTER, 0), o);
            o->op_type = OP_LEAVE;
            o->op_ppaddr = PL_ppaddr[OP_LEAVE];
        }
        else if (o->op_type == OP_LINESEQ) {
            OP *kid;
            o->op_type = OP_SCOPE;
            o->op_ppaddr = PL_ppaddr[OP_SCOPE];
            kid = ((LISTOP*)o)->op_first;
            if (kid->op_type == OP_NEXTSTATE || kid->op_type == OP_DBSTATE)
                op_null(kid);
        }
        else
            o = newLISTOP(OP_SCOPE, 0, o, Nullop);
    }
    return o;
}

/* XXX kept for BINCOMPAT only */
void
Perl_save_hints(pTHX)
{
    Perl_croak(aTHX_ "internal error: obsolete function save_hints() called");
}

int
Perl_block_start(pTHX_ int full)
{
    int retval = PL_savestack_ix;
    /* If there were syntax errors, don't try to start a block */
    if (PL_yynerrs) return retval;

    pad_block_start(full);
    SAVEHINTS();
    PL_hints &= ~HINT_BLOCK_SCOPE;
    SAVESPTR(PL_compiling.cop_warnings);
    if (! specialWARN(PL_compiling.cop_warnings)) {
        PL_compiling.cop_warnings = newSVsv(PL_compiling.cop_warnings) ;
        SAVEFREESV(PL_compiling.cop_warnings) ;
    }
    SAVESPTR(PL_compiling.cop_io);
    if (! specialCopIO(PL_compiling.cop_io)) {
        PL_compiling.cop_io = newSVsv(PL_compiling.cop_io) ;
        SAVEFREESV(PL_compiling.cop_io) ;
    }
    return retval;
}

OP*
Perl_block_end(pTHX_ I32 floor, OP *seq)
{
    int needblockscope = PL_hints & HINT_BLOCK_SCOPE;
    OP* retval = scalarseq(seq);
    /* If there were syntax errors, don't try to close a block */
    if (PL_yynerrs) return retval;
    LEAVE_SCOPE(floor);
    PL_compiling.op_private = (U8)(PL_hints & HINT_PRIVATE_MASK);
    if (needblockscope)
        PL_hints |= HINT_BLOCK_SCOPE; /* propagate out */
    pad_leavemy();
    return retval;
}

STATIC OP *
S_newDEFSVOP(pTHX)
{
#ifdef USE_5005THREADS
    OP *o = newOP(OP_THREADSV, 0);
    o->op_targ = find_threadsv("_");
    return o;
#else
    return newSVREF(newGVOP(OP_GV, 0, PL_defgv));
#endif /* USE_5005THREADS */
}

void
Perl_newPROG(pTHX_ OP *o)
{
    if (PL_in_eval) {
        if (PL_eval_root)
                return;
        PL_eval_root = newUNOP(OP_LEAVEEVAL,
                               ((PL_in_eval & EVAL_KEEPERR)
                                ? OPf_SPECIAL : 0), o);
        PL_eval_start = linklist(PL_eval_root);
        PL_eval_root->op_private |= OPpREFCOUNTED;
        OpREFCNT_set(PL_eval_root, 1);
        PL_eval_root->op_next = 0;
        CALL_PEEP(PL_eval_start);
    }
    else {
        if (o->op_type == OP_STUB) {
            PL_comppad_name = 0;
            PL_compcv = 0;
            FreeOp(o);
            return;
        }
        PL_main_root = scope(sawparens(scalarvoid(o)));
        PL_curcop = &PL_compiling;
        PL_main_start = LINKLIST(PL_main_root);
        PL_main_root->op_private |= OPpREFCOUNTED;
        OpREFCNT_set(PL_main_root, 1);
        PL_main_root->op_next = 0;
        CALL_PEEP(PL_main_start);
        PL_compcv = 0;

        /* Register with debugger */
        if (PERLDB_INTER) {
            CV *cv = get_cv("DB::postponed", FALSE);
            if (cv) {
                dSP;
                PUSHMARK(SP);
                XPUSHs((SV*)CopFILEGV(&PL_compiling));
                PUTBACK;
                call_sv((SV*)cv, G_DISCARD);
            }
        }
    }
}

OP *
Perl_localize(pTHX_ OP *o, I32 lex)
{
    if (o->op_flags & OPf_PARENS)
/* [perl #17376]: this appears to be premature, and results in code such as
   C< our(%x); > executing in list mode rather than void mode */
#if 0
        list(o);
#else
        ;
#endif
    else {
        if (ckWARN(WARN_PARENTHESIS)
            && PL_bufptr > PL_oldbufptr && PL_bufptr[-1] == ',')
        {
            char *s = PL_bufptr;
            bool sigil = FALSE;

            /* some heuristics to detect a potential error */
            while (*s && (strchr(", \t\n", *s)))
                s++;

            while (1) {
                if (*s && strchr("@$%*", *s) && *++s
                       && (isALNUM(*s) || UTF8_IS_CONTINUED(*s))) {
                    s++;
                    sigil = TRUE;
                    while (*s && (isALNUM(*s) || UTF8_IS_CONTINUED(*s)))
                        s++;
                    while (*s && (strchr(", \t\n", *s)))
                        s++;
                }
                else
                    break;
            }
            if (sigil && (*s == ';' || *s == '=')) {
                Perl_warner(aTHX_ packWARN(WARN_PARENTHESIS),
                                "Parentheses missing around \"%s\" list",
                                lex ? (PL_in_my == KEY_our ? "our" : "my")
                                : "local");
            }
        }
    }
    if (lex)
        o = my(o);
    else
        o = mod(o, OP_NULL);            /* a bit kludgey */
    PL_in_my = FALSE;
    PL_in_my_stash = Nullhv;
    return o;
}

OP *
Perl_jmaybe(pTHX_ OP *o)
{
    if (o->op_type == OP_LIST) {
        OP *o2;
#ifdef USE_5005THREADS
        o2 = newOP(OP_THREADSV, 0);
        o2->op_targ = find_threadsv(";");
#else
        o2 = newSVREF(newGVOP(OP_GV, 0, gv_fetchpv(";", TRUE, SVt_PV))),
#endif /* USE_5005THREADS */
        o = convert(OP_JOIN, 0, prepend_elem(OP_LIST, o2, o));
    }
    return o;
}

OP *
Perl_fold_constants(pTHX_ register OP *o)
{
    register OP *curop;
    I32 type = o->op_type;
    SV *sv;

    if (PL_opargs[type] & OA_RETSCALAR)
        scalar(o);
    if (PL_opargs[type] & OA_TARGET && !o->op_targ)
        o->op_targ = pad_alloc(type, SVs_PADTMP);

    /* integerize op, unless it happens to be C<-foo>.
     * XXX should pp_i_negate() do magic string negation instead? */
    if ((PL_opargs[type] & OA_OTHERINT) && (PL_hints & HINT_INTEGER)
        && !(type == OP_NEGATE && cUNOPo->op_first->op_type == OP_CONST
             && (cUNOPo->op_first->op_private & OPpCONST_BARE)))
    {
        o->op_ppaddr = PL_ppaddr[type = ++(o->op_type)];
    }

    if (!(PL_opargs[type] & OA_FOLDCONST))
        goto nope;

    switch (type) {
    case OP_NEGATE:
        /* XXX might want a ck_negate() for this */
        cUNOPo->op_first->op_private &= ~OPpCONST_STRICT;
        break;
    case OP_SPRINTF:
    case OP_UCFIRST:
    case OP_LCFIRST:
    case OP_UC:
    case OP_LC:
    case OP_SLT:
    case OP_SGT:
    case OP_SLE:
    case OP_SGE:
    case OP_SCMP:
        /* XXX what about the numeric ops? */
        if (PL_hints & HINT_LOCALE)
            goto nope;
    }

    if (PL_error_count)
        goto nope;              /* Don't try to run w/ errors */

    for (curop = LINKLIST(o); curop != o; curop = LINKLIST(curop)) {
        if ((curop->op_type != OP_CONST ||
             (curop->op_private & OPpCONST_BARE)) &&
            curop->op_type != OP_LIST &&
            curop->op_type != OP_SCALAR &&
            curop->op_type != OP_NULL &&
            curop->op_type != OP_PUSHMARK)
        {
            goto nope;
        }
    }

    curop = LINKLIST(o);
    o->op_next = 0;
    PL_op = curop;
    CALLRUNOPS(aTHX);
    sv = *(PL_stack_sp--);
    if (o->op_targ && sv == PAD_SV(o->op_targ)) /* grab pad temp? */
        pad_swipe(o->op_targ,  FALSE);
    else if (SvTEMP(sv)) {                      /* grab mortal temp? */
        (void)SvREFCNT_inc(sv);
        SvTEMP_off(sv);
    }
    op_free(o);
    if (type == OP_RV2GV)
        return newGVOP(OP_GV, 0, (GV*)sv);
    return newSVOP(OP_CONST, 0, sv);

  nope:
    return o;
}

OP *
Perl_gen_constant_list(pTHX_ register OP *o)
{
    register OP *curop;
    I32 oldtmps_floor = PL_tmps_floor;

    list(o);
    if (PL_error_count)
        return o;               /* Don't attempt to run with errors */

    PL_op = curop = LINKLIST(o);
    o->op_next = 0;
    CALL_PEEP(curop);
    pp_pushmark();
    CALLRUNOPS(aTHX);
    PL_op = curop;
    pp_anonlist();
    PL_tmps_floor = oldtmps_floor;

    o->op_type = OP_RV2AV;
    o->op_ppaddr = PL_ppaddr[OP_RV2AV];
    o->op_flags &= ~OPf_REF;    /* treat \(1..2) like an ordinary list */
    o->op_flags |= OPf_PARENS;  /* and flatten \(1..2,3) */
    o->op_seq = 0;              /* needs to be revisited in peep() */
    curop = ((UNOP*)o)->op_first;
    ((UNOP*)o)->op_first = newSVOP(OP_CONST, 0, SvREFCNT_inc(*PL_stack_sp--));
    op_free(curop);
    linklist(o);
    return list(o);
}

OP *
Perl_convert(pTHX_ I32 type, I32 flags, OP *o)
{
    if (!o || o->op_type != OP_LIST)
        o = newLISTOP(OP_LIST, 0, o, Nullop);
    else
        o->op_flags &= ~OPf_WANT;

    if (!(PL_opargs[type] & OA_MARK))
        op_null(cLISTOPo->op_first);

    o->op_type = (OPCODE)type;
    o->op_ppaddr = PL_ppaddr[type];
    o->op_flags |= flags;

    o = CHECKOP(type, o);
    if (o->op_type != (unsigned)type)
        return o;

    return fold_constants(o);
}

/* List constructors */

OP *
Perl_append_elem(pTHX_ I32 type, OP *first, OP *last)
{
    if (!first)
        return last;

    if (!last)
        return first;

    if (first->op_type != (unsigned)type
        || (type == OP_LIST && (first->op_flags & OPf_PARENS)))
    {
        return newLISTOP(type, 0, first, last);
    }

    if (first->op_flags & OPf_KIDS)
        ((LISTOP*)first)->op_last->op_sibling = last;
    else {
        first->op_flags |= OPf_KIDS;
        ((LISTOP*)first)->op_first = last;
    }
    ((LISTOP*)first)->op_last = last;
    return first;
}

OP *
Perl_append_list(pTHX_ I32 type, LISTOP *first, LISTOP *last)
{
    if (!first)
        return (OP*)last;

    if (!last)
        return (OP*)first;

    if (first->op_type != (unsigned)type)
        return prepend_elem(type, (OP*)first, (OP*)last);

    if (last->op_type != (unsigned)type)
        return append_elem(type, (OP*)first, (OP*)last);

    first->op_last->op_sibling = last->op_first;
    first->op_last = last->op_last;
    first->op_flags |= (last->op_flags & OPf_KIDS);

    FreeOp(last);

    return (OP*)first;
}

OP *
Perl_prepend_elem(pTHX_ I32 type, OP *first, OP *last)
{
    if (!first)
        return last;

    if (!last)
        return first;

    if (last->op_type == (unsigned)type) {
        if (type == OP_LIST) {  /* already a PUSHMARK there */
            first->op_sibling = ((LISTOP*)last)->op_first->op_sibling;
            ((LISTOP*)last)->op_first->op_sibling = first;
            if (!(first->op_flags & OPf_PARENS))
                last->op_flags &= ~OPf_PARENS;
        }
        else {
            if (!(last->op_flags & OPf_KIDS)) {
                ((LISTOP*)last)->op_last = first;
                last->op_flags |= OPf_KIDS;
            }
            first->op_sibling = ((LISTOP*)last)->op_first;
            ((LISTOP*)last)->op_first = first;
        }
        last->op_flags |= OPf_KIDS;
        return last;
    }

    return newLISTOP(type, 0, first, last);
}

/* Constructors */

OP *
Perl_newNULLLIST(pTHX)
{
    return newOP(OP_STUB, 0);
}

OP *
Perl_force_list(pTHX_ OP *o)
{
    if (!o || o->op_type != OP_LIST)
        o = newLISTOP(OP_LIST, 0, o, Nullop);
    op_null(o);
    return o;
}

OP *
Perl_newLISTOP(pTHX_ I32 type, I32 flags, OP *first, OP *last)
{
    LISTOP *listop;

    NewOp(1101, listop, 1, LISTOP);

    listop->op_type = (OPCODE)type;
    listop->op_ppaddr = PL_ppaddr[type];
    if (first || last)
        flags |= OPf_KIDS;
    listop->op_flags = (U8)flags;

    if (!last && first)
        last = first;
    else if (!first && last)
        first = last;
    else if (first)
        first->op_sibling = last;
    listop->op_first = first;
    listop->op_last = last;
    if (type == OP_LIST) {
        OP* pushop;
        pushop = newOP(OP_PUSHMARK, 0);
        pushop->op_sibling = first;
        listop->op_first = pushop;
        listop->op_flags |= OPf_KIDS;
        if (!last)
            listop->op_last = pushop;
    }

    return CHECKOP(type, listop);
}

OP *
Perl_newOP(pTHX_ I32 type, I32 flags)
{
    OP *o;
    NewOp(1101, o, 1, OP);
    o->op_type = (OPCODE)type;
    o->op_ppaddr = PL_ppaddr[type];
    o->op_flags = (U8)flags;

    o->op_next = o;
    o->op_private = (U8)(0 | (flags >> 8));
    if (PL_opargs[type] & OA_RETSCALAR)
        scalar(o);
    if (PL_opargs[type] & OA_TARGET)
        o->op_targ = pad_alloc(type, SVs_PADTMP);
    return CHECKOP(type, o);
}

OP *
Perl_newUNOP(pTHX_ I32 type, I32 flags, OP *first)
{
    UNOP *unop;

    if (!first)
        first = newOP(OP_STUB, 0);
    if (PL_opargs[type] & OA_MARK)
        first = force_list(first);

    NewOp(1101, unop, 1, UNOP);
    unop->op_type = (OPCODE)type;
    unop->op_ppaddr = PL_ppaddr[type];
    unop->op_first = first;
    unop->op_flags = flags | OPf_KIDS;
    unop->op_private = (U8)(1 | (flags >> 8));
    unop = (UNOP*) CHECKOP(type, unop);
    if (unop->op_next)
        return (OP*)unop;

    return fold_constants((OP *) unop);
}

OP *
Perl_newBINOP(pTHX_ I32 type, I32 flags, OP *first, OP *last)
{
    BINOP *binop;
    NewOp(1101, binop, 1, BINOP);

    if (!first)
        first = newOP(OP_NULL, 0);

    binop->op_type = (OPCODE)type;
    binop->op_ppaddr = PL_ppaddr[type];
    binop->op_first = first;
    binop->op_flags = flags | OPf_KIDS;
    if (!last) {
        last = first;
        binop->op_private = (U8)(1 | (flags >> 8));
    }
    else {
        binop->op_private = (U8)(2 | (flags >> 8));
        first->op_sibling = last;
    }

    binop = (BINOP*)CHECKOP(type, binop);
    if (binop->op_next || binop->op_type != (OPCODE)type)
        return (OP*)binop;

    binop->op_last = binop->op_first->op_sibling;

    return fold_constants((OP *)binop);
}

static int
uvcompare(const void *a, const void *b)
{
    if (*((UV *)a) < (*(UV *)b))
        return -1;
    if (*((UV *)a) > (*(UV *)b))
        return 1;
    if (*((UV *)a+1) < (*(UV *)b+1))
        return -1;
    if (*((UV *)a+1) > (*(UV *)b+1))
        return 1;
    return 0;
}

OP *
Perl_pmtrans(pTHX_ OP *o, OP *expr, OP *repl)
{
    SV *tstr = ((SVOP*)expr)->op_sv;
    SV *rstr = ((SVOP*)repl)->op_sv;
    STRLEN tlen;
    STRLEN rlen;
    U8 *t = (U8*)SvPV(tstr, tlen);
    U8 *r = (U8*)SvPV(rstr, rlen);
    register I32 i;
    register I32 j;
    I32 del;
    I32 complement;
    I32 squash;
    I32 grows = 0;
    register short *tbl;

    PL_hints |= HINT_BLOCK_SCOPE;
    complement  = o->op_private & OPpTRANS_COMPLEMENT;
    del         = o->op_private & OPpTRANS_DELETE;
    squash      = o->op_private & OPpTRANS_SQUASH;

    if (SvUTF8(tstr))
        o->op_private |= OPpTRANS_FROM_UTF;

    if (SvUTF8(rstr))
        o->op_private |= OPpTRANS_TO_UTF;

    if (o->op_private & (OPpTRANS_FROM_UTF|OPpTRANS_TO_UTF)) {
        SV* listsv = newSVpvn("# comment\n",10);
        SV* transv = 0;
        U8* tend = t + tlen;
        U8* rend = r + rlen;
        STRLEN ulen;
        UV tfirst = 1;
        UV tlast = 0;
        IV tdiff;
        UV rfirst = 1;
        UV rlast = 0;
        IV rdiff;
        IV diff;
        I32 none = 0;
        U32 max = 0;
        I32 bits;
        I32 havefinal = 0;
        U32 final = 0;
        I32 from_utf    = o->op_private & OPpTRANS_FROM_UTF;
        I32 to_utf      = o->op_private & OPpTRANS_TO_UTF;
        U8* tsave = NULL;
        U8* rsave = NULL;

        if (!from_utf) {
            STRLEN len = tlen;
            tsave = t = bytes_to_utf8(t, &len);
            tend = t + len;
        }
        if (!to_utf && rlen) {
            STRLEN len = rlen;
            rsave = r = bytes_to_utf8(r, &len);
            rend = r + len;
        }

/* There are several snags with this code on EBCDIC:
   1. 0xFF is a legal UTF-EBCDIC byte (there are no illegal bytes).
   2. scan_const() in toke.c has encoded chars in native encoding which makes
      ranges at least in EBCDIC 0..255 range the bottom odd.
*/

        if (complement) {
            U8 tmpbuf[UTF8_MAXBYTES+1];
            UV *cp;
            UV nextmin = 0;
            New(1109, cp, 2*tlen, UV);
            i = 0;
            transv = newSVpvn("",0);
            while (t < tend) {
                cp[2*i] = utf8n_to_uvuni(t, tend-t, &ulen, 0);
                t += ulen;
                if (t < tend && NATIVE_TO_UTF(*t) == 0xff) {
                    t++;
                    cp[2*i+1] = utf8n_to_uvuni(t, tend-t, &ulen, 0);
                    t += ulen;
                }
                else {
                 cp[2*i+1] = cp[2*i];
                }
                i++;
            }
            qsort(cp, i, 2*sizeof(UV), uvcompare);
            for (j = 0; j < i; j++) {
                UV  val = cp[2*j];
                diff = val - nextmin;
                if (diff > 0) {
                    t = uvuni_to_utf8(tmpbuf,nextmin);
                    sv_catpvn(transv, (char*)tmpbuf, t - tmpbuf);
                    if (diff > 1) {
                        U8  range_mark = UTF_TO_NATIVE(0xff);
                        t = uvuni_to_utf8(tmpbuf, val - 1);
                        sv_catpvn(transv, (char *)&range_mark, 1);
                        sv_catpvn(transv, (char*)tmpbuf, t - tmpbuf);
                    }
                }
                val = cp[2*j+1];
                if (val >= nextmin)
                    nextmin = val + 1;
            }
            t = uvuni_to_utf8(tmpbuf,nextmin);
            sv_catpvn(transv, (char*)tmpbuf, t - tmpbuf);
            {
                U8 range_mark = UTF_TO_NATIVE(0xff);
                sv_catpvn(transv, (char *)&range_mark, 1);
            }
            t = uvuni_to_utf8_flags(tmpbuf, 0x7fffffff,
                                    UNICODE_ALLOW_SUPER);
            sv_catpvn(transv, (char*)tmpbuf, t - tmpbuf);
            t = (U8*)SvPVX(transv);
            tlen = SvCUR(transv);
            tend = t + tlen;
            Safefree(cp);
        }
        else if (!rlen && !del) {
            r = t; rlen = tlen; rend = tend;
        }
        if (!squash) {
                if ((!rlen && !del) || t == r ||
                    (tlen == rlen && memEQ((char *)t, (char *)r, tlen)))
                {
                    o->op_private |= OPpTRANS_IDENTICAL;
                }
        }

        while (t < tend || tfirst <= tlast) {
            /* see if we need more "t" chars */
            if (tfirst > tlast) {
                tfirst = (I32)utf8n_to_uvuni(t, tend - t, &ulen, 0);
                t += ulen;
                if (t < tend && NATIVE_TO_UTF(*t) == 0xff) {    /* illegal utf8 val indicates range */
                    t++;
                    tlast = (I32)utf8n_to_uvuni(t, tend - t, &ulen, 0);
                    t += ulen;
                }
                else
                    tlast = tfirst;
            }

            /* now see if we need more "r" chars */
            if (rfirst > rlast) {
                if (r < rend) {
                    rfirst = (I32)utf8n_to_uvuni(r, rend - r, &ulen, 0);
                    r += ulen;
                    if (r < rend && NATIVE_TO_UTF(*r) == 0xff) {        /* illegal utf8 val indicates range */
                        r++;
                        rlast = (I32)utf8n_to_uvuni(r, rend - r, &ulen, 0);
                        r += ulen;
                    }
                    else
                        rlast = rfirst;
                }
                else {
                    if (!havefinal++)
                        final = rlast;
                    rfirst = rlast = 0xffffffff;
                }
            }

            /* now see which range will peter our first, if either. */
            tdiff = tlast - tfirst;
            rdiff = rlast - rfirst;

            if (tdiff <= rdiff)
                diff = tdiff;
            else
                diff = rdiff;

            if (rfirst == 0xffffffff) {
                diff = tdiff;   /* oops, pretend rdiff is infinite */
                if (diff > 0)
                    Perl_sv_catpvf(aTHX_ listsv, "%04lx\t%04lx\tXXXX\n",
                                   (long)tfirst, (long)tlast);
                else
                    Perl_sv_catpvf(aTHX_ listsv, "%04lx\t\tXXXX\n", (long)tfirst);
            }
            else {
                if (diff > 0)
                    Perl_sv_catpvf(aTHX_ listsv, "%04lx\t%04lx\t%04lx\n",
                                   (long)tfirst, (long)(tfirst + diff),
                                   (long)rfirst);
                else
                    Perl_sv_catpvf(aTHX_ listsv, "%04lx\t\t%04lx\n",
                                   (long)tfirst, (long)rfirst);

                if (rfirst + diff > max)
                    max = rfirst + diff;
                if (!grows)
                    grows = (tfirst < rfirst &&
                             UNISKIP(tfirst) < UNISKIP(rfirst + diff));
                rfirst += diff + 1;
            }
            tfirst += diff + 1;
        }

        none = ++max;
        if (del)
            del = ++max;

        if (max > 0xffff)
            bits = 32;
        else if (max > 0xff)
            bits = 16;
        else
            bits = 8;

        Safefree(cPVOPo->op_pv);
        cSVOPo->op_sv = (SV*)swash_init("utf8", "", listsv, bits, none);
        SvREFCNT_dec(listsv);
        if (transv)
            SvREFCNT_dec(transv);

        if (!del && havefinal && rlen)
            (void)hv_store((HV*)SvRV((cSVOPo->op_sv)), "FINAL", 5,
                           newSVuv((UV)final), 0);

        if (grows)
            o->op_private |= OPpTRANS_GROWS;

        if (tsave)
            Safefree(tsave);
        if (rsave)
            Safefree(rsave);

        op_free(expr);
        op_free(repl);
        return o;
    }

    tbl = (short*)cPVOPo->op_pv;
    if (complement) {
        Zero(tbl, 256, short);
        for (i = 0; i < (I32)tlen; i++)
            tbl[t[i]] = -1;
        for (i = 0, j = 0; i < 256; i++) {
            if (!tbl[i]) {
                if (j >= (I32)rlen) {
                    if (del)
                        tbl[i] = -2;
                    else if (rlen)
                        tbl[i] = r[j-1];
                    else
                        tbl[i] = (short)i;
                }
                else {
                    if (i < 128 && r[j] >= 128)
                        grows = 1;
                    tbl[i] = r[j++];
                }
            }
        }
        if (!del) {
            if (!rlen) {
                j = rlen;
                if (!squash)
                    o->op_private |= OPpTRANS_IDENTICAL;
            }
            else if (j >= (I32)rlen)
                j = rlen - 1;
            else
                cPVOPo->op_pv = (char*)Renew(tbl, 0x101+rlen-j, short);
            tbl[0x100] = rlen - j;
            for (i=0; i < (I32)rlen - j; i++)
                tbl[0x101+i] = r[j+i];
        }
    }
    else {
        if (!rlen && !del) {
            r = t; rlen = tlen;
            if (!squash)
                o->op_private |= OPpTRANS_IDENTICAL;
        }
        else if (!squash && rlen == tlen && memEQ((char*)t, (char*)r, tlen)) {
            o->op_private |= OPpTRANS_IDENTICAL;
        }
        for (i = 0; i < 256; i++)
            tbl[i] = -1;
        for (i = 0, j = 0; i < (I32)tlen; i++,j++) {
            if (j >= (I32)rlen) {
                if (del) {
                    if (tbl[t[i]] == -1)
                        tbl[t[i]] = -2;
                    continue;
                }
                --j;
            }
            if (tbl[t[i]] == -1) {
                if (t[i] < 128 && r[j] >= 128)
                    grows = 1;
                tbl[t[i]] = r[j];
            }
        }
    }
    if (grows)
        o->op_private |= OPpTRANS_GROWS;
    op_free(expr);
    op_free(repl);

    return o;
}

OP *
Perl_newPMOP(pTHX_ I32 type, I32 flags)
{
    PMOP *pmop;

    NewOp(1101, pmop, 1, PMOP);
    pmop->op_type = (OPCODE)type;
    pmop->op_ppaddr = PL_ppaddr[type];
    pmop->op_flags = (U8)flags;
    pmop->op_private = (U8)(0 | (flags >> 8));

    if (PL_hints & HINT_RE_TAINT)
        pmop->op_pmpermflags |= PMf_RETAINT;
    if (PL_hints & HINT_LOCALE)
        pmop->op_pmpermflags |= PMf_LOCALE;
    pmop->op_pmflags = pmop->op_pmpermflags;

#ifdef USE_ITHREADS
    {
        SV* repointer;
        if(av_len((AV*) PL_regex_pad[0]) > -1) {
            repointer = av_pop((AV*)PL_regex_pad[0]);
            pmop->op_pmoffset = SvIV(repointer);
            SvREPADTMP_off(repointer);
            sv_setiv(repointer,0);
        } else {
            repointer = newSViv(0);
            av_push(PL_regex_padav,SvREFCNT_inc(repointer));
            pmop->op_pmoffset = av_len(PL_regex_padav);
            PL_regex_pad = AvARRAY(PL_regex_padav);
        }
    }
#endif

        /* link into pm list */
    if (type != OP_TRANS && PL_curstash) {
        pmop->op_pmnext = HvPMROOT(PL_curstash);
        HvPMROOT(PL_curstash) = pmop;
        PmopSTASH_set(pmop,PL_curstash);
    }

    return CHECKOP(type, pmop);
}

OP *
Perl_pmruntime(pTHX_ OP *o, OP *expr, OP *repl)
{
    PMOP *pm;
    LOGOP *rcop;
    I32 repl_has_vars = 0;

    if (o->op_type == OP_TRANS)
        return pmtrans(o, expr, repl);

    PL_hints |= HINT_BLOCK_SCOPE;
    pm = (PMOP*)o;

    if (expr->op_type == OP_CONST) {
        STRLEN plen;
        SV *pat = ((SVOP*)expr)->op_sv;
        char *p = SvPV(pat, plen);
        if ((o->op_flags & OPf_SPECIAL) && (*p == ' ' && p[1] == '\0')) {
            sv_setpvn(pat, "\\s+", 3);
            p = SvPV(pat, plen);
            pm->op_pmflags |= PMf_SKIPWHITE;
        }
        if (DO_UTF8(pat))
            pm->op_pmdynflags |= PMdf_UTF8;
        PM_SETRE(pm, CALLREGCOMP(aTHX_ p, p + plen, pm));
        if (strEQ("\\s+", PM_GETRE(pm)->precomp))
            pm->op_pmflags |= PMf_WHITE;
        op_free(expr);
    }
    else {
        if (pm->op_pmflags & PMf_KEEP || !(PL_hints & HINT_RE_EVAL))
            expr = newUNOP((!(PL_hints & HINT_RE_EVAL)
                            ? OP_REGCRESET
                            : OP_REGCMAYBE),0,expr);

        NewOp(1101, rcop, 1, LOGOP);
        rcop->op_type = OP_REGCOMP;
        rcop->op_ppaddr = PL_ppaddr[OP_REGCOMP];
        rcop->op_first = scalar(expr);
        rcop->op_flags |= ((PL_hints & HINT_RE_EVAL)
                           ? (OPf_SPECIAL | OPf_KIDS)
                           : OPf_KIDS);
        rcop->op_private = 1;
        rcop->op_other = o;

        /* establish postfix order */
        if (pm->op_pmflags & PMf_KEEP || !(PL_hints & HINT_RE_EVAL)) {
            LINKLIST(expr);
            rcop->op_next = expr;
            ((UNOP*)expr)->op_first->op_next = (OP*)rcop;
        }
        else {
            rcop->op_next = LINKLIST(expr);
            expr->op_next = (OP*)rcop;
        }

        prepend_elem(o->op_type, scalar((OP*)rcop), o);
    }

    if (repl) {
        OP *curop;
        if (pm->op_pmflags & PMf_EVAL) {
            curop = 0;
            if (CopLINE(PL_curcop) < (line_t)PL_multi_end)
                CopLINE_set(PL_curcop, (line_t)PL_multi_end);
        }
#ifdef USE_5005THREADS
        else if (repl->op_type == OP_THREADSV
                 && strchr("&`'123456789+",
                           PL_threadsv_names[repl->op_targ]))
        {
            curop = 0;
        }
#endif /* USE_5005THREADS */
        else if (repl->op_type == OP_CONST)
            curop = repl;
        else {
            OP *lastop = 0;
            for (curop = LINKLIST(repl); curop!=repl; curop = LINKLIST(curop)) {
                if (PL_opargs[curop->op_type] & OA_DANGEROUS) {
#ifdef USE_5005THREADS
                    if (curop->op_type == OP_THREADSV) {
                        repl_has_vars = 1;
                        if (strchr("&`'123456789+", curop->op_private))
                            break;
                    }
#else
                    if (curop->op_type == OP_GV) {
                        GV *gv = cGVOPx_gv(curop);
                        repl_has_vars = 1;
                        if (strchr("&`'123456789+-\016\022", *GvENAME(gv)))
                            break;
                    }
#endif /* USE_5005THREADS */
                    else if (curop->op_type == OP_RV2CV)
                        break;
                    else if (curop->op_type == OP_RV2SV ||
                             curop->op_type == OP_RV2AV ||
                             curop->op_type == OP_RV2HV ||
                             curop->op_type == OP_RV2GV) {
                        if (lastop && lastop->op_type != OP_GV) /*funny deref?*/
                            break;
                    }
                    else if (curop->op_type == OP_PADSV ||
                             curop->op_type == OP_PADAV ||
                             curop->op_type == OP_PADHV ||
                             curop->op_type == OP_PADANY) {
                        repl_has_vars = 1;
                    }
                    else if (curop->op_type == OP_PUSHRE)
                        ; /* Okay here, dangerous in newASSIGNOP */
                    else
                        break;
                }
                lastop = curop;
            }
        }
        if (curop == repl
            && !(repl_has_vars
                 && (!PM_GETRE(pm)
                     || PM_GETRE(pm)->reganch & ROPT_EVAL_SEEN))) {
            pm->op_pmflags |= PMf_CONST;        /* const for long enough */
            pm->op_pmpermflags |= PMf_CONST;    /* const for long enough */
            prepend_elem(o->op_type, scalar(repl), o);
        }
        else {
            if (curop == repl && !PM_GETRE(pm)) { /* Has variables. */
                pm->op_pmflags |= PMf_MAYBE_CONST;
                pm->op_pmpermflags |= PMf_MAYBE_CONST;
            }
            NewOp(1101, rcop, 1, LOGOP);
            rcop->op_type = OP_SUBSTCONT;
            rcop->op_ppaddr = PL_ppaddr[OP_SUBSTCONT];
            rcop->op_first = scalar(repl);
            rcop->op_flags |= OPf_KIDS;
            rcop->op_private = 1;
            rcop->op_other = o;

            /* establish postfix order */
            rcop->op_next = LINKLIST(repl);
            repl->op_next = (OP*)rcop;

            pm->op_pmreplroot = scalar((OP*)rcop);
            pm->op_pmreplstart = LINKLIST(rcop);
            rcop->op_next = 0;
        }
    }

    return (OP*)pm;
}

OP *
Perl_newSVOP(pTHX_ I32 type, I32 flags, SV *sv)
{
    SVOP *svop;
    NewOp(1101, svop, 1, SVOP);
    svop->op_type = (OPCODE)type;
    svop->op_ppaddr = PL_ppaddr[type];
    svop->op_sv = sv;
    svop->op_next = (OP*)svop;
    svop->op_flags = (U8)flags;
    if (PL_opargs[type] & OA_RETSCALAR)
        scalar((OP*)svop);
    if (PL_opargs[type] & OA_TARGET)
        svop->op_targ = pad_alloc(type, SVs_PADTMP);
    return CHECKOP(type, svop);
}

OP *
Perl_newPADOP(pTHX_ I32 type, I32 flags, SV *sv)
{
    PADOP *padop;
    NewOp(1101, padop, 1, PADOP);
    padop->op_type = (OPCODE)type;
    padop->op_ppaddr = PL_ppaddr[type];
    padop->op_padix = pad_alloc(type, SVs_PADTMP);
    SvREFCNT_dec(PAD_SVl(padop->op_padix));
    PAD_SETSV(padop->op_padix, sv);
    if (sv)
        SvPADTMP_on(sv);
    padop->op_next = (OP*)padop;
    padop->op_flags = (U8)flags;
    if (PL_opargs[type] & OA_RETSCALAR)
        scalar((OP*)padop);
    if (PL_opargs[type] & OA_TARGET)
        padop->op_targ = pad_alloc(type, SVs_PADTMP);
    return CHECKOP(type, padop);
}

OP *
Perl_newGVOP(pTHX_ I32 type, I32 flags, GV *gv)
{
#ifdef USE_ITHREADS
    if (gv)
        GvIN_PAD_on(gv);
    return newPADOP(type, flags, SvREFCNT_inc(gv));
#else
    return newSVOP(type, flags, SvREFCNT_inc(gv));
#endif
}

OP *
Perl_newPVOP(pTHX_ I32 type, I32 flags, char *pv)
{
    PVOP *pvop;
    NewOp(1101, pvop, 1, PVOP);
    pvop->op_type = (OPCODE)type;
    pvop->op_ppaddr = PL_ppaddr[type];
    pvop->op_pv = pv;
    pvop->op_next = (OP*)pvop;
    pvop->op_flags = (U8)flags;
    if (PL_opargs[type] & OA_RETSCALAR)
        scalar((OP*)pvop);
    if (PL_opargs[type] & OA_TARGET)
        pvop->op_targ = pad_alloc(type, SVs_PADTMP);
    return CHECKOP(type, pvop);
}

void
Perl_package(pTHX_ OP *o)
{
    SV *sv;

    save_hptr(&PL_curstash);
    save_item(PL_curstname);
    if (o) {
        STRLEN len;
        char *name;
        sv = cSVOPo->op_sv;
        name = SvPV(sv, len);
        PL_curstash = gv_stashpvn(name,len,TRUE);
        sv_setpvn(PL_curstname, name, len);
        op_free(o);
    }
    else {
        deprecate("\"package\" with no arguments");
        sv_setpv(PL_curstname,"<none>");
        PL_curstash = Nullhv;
    }
    PL_hints |= HINT_BLOCK_SCOPE;
    PL_copline = NOLINE;
    PL_expect = XSTATE;
}

void
Perl_utilize(pTHX_ int aver, I32 floor, OP *version, OP *idop, OP *arg)
{
    OP *pack;
    OP *imop;
    OP *veop;

    if (idop->op_type != OP_CONST)
        Perl_croak(aTHX_ "Module name must be constant");

    veop = Nullop;

    if (version != Nullop) {
        SV *vesv = ((SVOP*)version)->op_sv;

        if (arg == Nullop && !SvNIOKp(vesv)) {
            arg = version;
        }
        else {
            OP *pack;
            SV *meth;

            if (version->op_type != OP_CONST || !SvNIOKp(vesv))
                Perl_croak(aTHX_ "Version number must be constant number");

            /* Make copy of idop so we don't free it twice */
            pack = newSVOP(OP_CONST, 0, newSVsv(((SVOP*)idop)->op_sv));

            /* Fake up a method call to VERSION */
            meth = newSVpvn("VERSION",7);
            sv_upgrade(meth, SVt_PVIV);
            (void)SvIOK_on(meth);
            PERL_HASH(SvUVX(meth), SvPVX(meth), SvCUR(meth));
            veop = convert(OP_ENTERSUB, OPf_STACKED|OPf_SPECIAL,
                            append_elem(OP_LIST,
                                        prepend_elem(OP_LIST, pack, list(version)),
                                        newSVOP(OP_METHOD_NAMED, 0, meth)));
        }
    }

    /* Fake up an import/unimport */
    if (arg && arg->op_type == OP_STUB)
        imop = arg;             /* no import on explicit () */
    else if (SvNIOKp(((SVOP*)idop)->op_sv)) {
        imop = Nullop;          /* use 5.0; */
    }
    else {
        SV *meth;

        /* Make copy of idop so we don't free it twice */
        pack = newSVOP(OP_CONST, 0, newSVsv(((SVOP*)idop)->op_sv));

        /* Fake up a method call to import/unimport */
        meth = aver ? newSVpvn("import",6) : newSVpvn("unimport", 8);
        (void)SvUPGRADE(meth, SVt_PVIV);
        (void)SvIOK_on(meth);
        PERL_HASH(SvUVX(meth), SvPVX(meth), SvCUR(meth));
        imop = convert(OP_ENTERSUB, OPf_STACKED|OPf_SPECIAL,
                       append_elem(OP_LIST,
                                   prepend_elem(OP_LIST, pack, list(arg)),
                                   newSVOP(OP_METHOD_NAMED, 0, meth)));
    }

    /* Fake up the BEGIN {}, which does its thing immediately. */
    newATTRSUB(floor,
        newSVOP(OP_CONST, 0, newSVpvn("BEGIN", 5)),
        Nullop,
        Nullop,
        append_elem(OP_LINESEQ,
            append_elem(OP_LINESEQ,
                newSTATEOP(0, Nullch, newUNOP(OP_REQUIRE, 0, idop)),
                newSTATEOP(0, Nullch, veop)),
            newSTATEOP(0, Nullch, imop) ));

    /* The "did you use incorrect case?" warning used to be here.
     * The problem is that on case-insensitive filesystems one
     * might get false positives for "use" (and "require"):
     * "use Strict" or "require CARP" will work.  This causes
     * portability problems for the script: in case-strict
     * filesystems the script will stop working.
     *
     * The "incorrect case" warning checked whether "use Foo"
     * imported "Foo" to your namespace, but that is wrong, too:
     * there is no requirement nor promise in the language that
     * a Foo.pm should or would contain anything in package "Foo".
     *
     * There is very little Configure-wise that can be done, either:
     * the case-sensitivity of the build filesystem of Perl does not
     * help in guessing the case-sensitivity of the runtime environment.
     */

    PL_hints |= HINT_BLOCK_SCOPE;
    PL_copline = NOLINE;
    PL_expect = XSTATE;
    PL_cop_seqmax++; /* Purely for B::*'s benefit */
}

/*
=head1 Embedding Functions

=for apidoc load_module

Loads the module whose name is pointed to by the string part of name.
Note that the actual module name, not its filename, should be given.
Eg, "Foo::Bar" instead of "Foo/Bar.pm".  flags can be any of
PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or PERL_LOADMOD_IMPORT_OPS
(or 0 for no flags). ver, if specified, provides version semantics
similar to C<use Foo::Bar VERSION>.  The optional trailing SV*
arguments can be used to specify arguments to the module's import()
method, similar to C<use Foo::Bar VERSION LIST>.

=cut */

void
Perl_load_module(pTHX_ U32 flags, SV *name, SV *ver, ...)
{
    va_list args;
    va_start(args, ver);
    vload_module(flags, name, ver, &args);
    va_end(args);
}

#ifdef PERL_IMPLICIT_CONTEXT
void
Perl_load_module_nocontext(U32 flags, SV *name, SV *ver, ...)
{
    dTHX;
    va_list args;
    va_start(args, ver);
    vload_module(flags, name, ver, &args);
    va_end(args);
}
#endif

void
Perl_vload_module(pTHX_ U32 flags, SV *name, SV *ver, va_list *args)
{
    OP *modname, *veop, *imop;

    modname = newSVOP(OP_CONST, 0, name);
    modname->op_private |= OPpCONST_BARE;
    if (ver) {
        veop = newSVOP(OP_CONST, 0, ver);
    }
    else
        veop = Nullop;
    if (flags & PERL_LOADMOD_NOIMPORT) {
        imop = sawparens(newNULLLIST());
    }
    else if (flags & PERL_LOADMOD_IMPORT_OPS) {
        imop = va_arg(*args, OP*);
    }
    else {
        SV *sv;
        imop = Nullop;
        sv = va_arg(*args, SV*);
        while (sv) {
            imop = append_elem(OP_LIST, imop, newSVOP(OP_CONST, 0, sv));
            sv = va_arg(*args, SV*);
        }
    }
    {
        line_t ocopline = PL_copline;
        COP *ocurcop = PL_curcop;
        int oexpect = PL_expect;

        utilize(!(flags & PERL_LOADMOD_DENY), start_subparse(FALSE, 0),
                veop, modname, imop);
        PL_expect = oexpect;
        PL_copline = ocopline;
        PL_curcop = ocurcop;
    }
}

OP *
Perl_dofile(pTHX_ OP *term)
{
    OP *doop;
    GV *gv;

    gv = gv_fetchpv("do", FALSE, SVt_PVCV);
    if (!(gv && GvCVu(gv) && GvIMPORTED_CV(gv)))
        gv = gv_fetchpv("CORE::GLOBAL::do", FALSE, SVt_PVCV);

    if (gv && GvCVu(gv) && GvIMPORTED_CV(gv)) {
        doop = ck_subr(newUNOP(OP_ENTERSUB, OPf_STACKED,
                               append_elem(OP_LIST, term,
                                           scalar(newUNOP(OP_RV2CV, 0,
                                                          newGVOP(OP_GV, 0,
                                                                  gv))))));
    }
    else {
        doop = newUNOP(OP_DOFILE, 0, scalar(term));
    }
    return doop;
}

OP *
Perl_newSLICEOP(pTHX_ I32 flags, OP *subscript, OP *listval)
{
    return newBINOP(OP_LSLICE, flags,
            list(force_list(subscript)),
            list(force_list(listval)) );
}

STATIC I32
S_list_assignment(pTHX_ register OP *o)
{
    if (!o)
        return TRUE;

    if (o->op_type == OP_NULL && o->op_flags & OPf_KIDS)
        o = cUNOPo->op_first;

    if (o->op_type == OP_COND_EXPR) {
        I32 t = list_assignment(cLOGOPo->op_first->op_sibling);
        I32 f = list_assignment(cLOGOPo->op_first->op_sibling->op_sibling);

        if (t && f)
            return TRUE;
        if (t || f)
            yyerror("Assignment to both a list and a scalar");
        return FALSE;
    }

    if (o->op_type == OP_LIST &&
        (o->op_flags & OPf_WANT) == OPf_WANT_SCALAR &&
        o->op_private & OPpLVAL_INTRO)
        return FALSE;

    if (o->op_type == OP_LIST || o->op_flags & OPf_PARENS ||
        o->op_type == OP_RV2AV || o->op_type == OP_RV2HV ||
        o->op_type == OP_ASLICE || o->op_type == OP_HSLICE)
        return TRUE;

    if (o->op_type == OP_PADAV || o->op_type == OP_PADHV)
        return TRUE;

    if (o->op_type == OP_RV2SV)
        return FALSE;

    return FALSE;
}

OP *
Perl_newASSIGNOP(pTHX_ I32 flags, OP *left, I32 optype, OP *right)
{
    OP *o;

    if (optype) {
        if (optype == OP_ANDASSIGN || optype == OP_ORASSIGN) {
            return newLOGOP(optype, 0,
                mod(scalar(left), optype),
                newUNOP(OP_SASSIGN, 0, scalar(right)));
        }
        else {
            return newBINOP(optype, OPf_STACKED,
                mod(scalar(left), optype), scalar(right));
        }
    }

    if (list_assignment(left)) {
        OP *curop;

        PL_modcount = 0;
        PL_eval_start = right;  /* Grandfathering $[ assignment here.  Bletch.*/
        left = mod(left, OP_AASSIGN);
        if (PL_eval_start)
            PL_eval_start = 0;
        else {
            op_free(left);
            op_free(right);
            return Nullop;
        }
        /* optimise C<my @x = ()> to C<my @x>, and likewise for hashes */
        if ((left->op_type == OP_PADAV || left->op_type == OP_PADHV)
                && right->op_type == OP_STUB
                && (left->op_private & OPpLVAL_INTRO))
        {
            op_free(right);
            left->op_flags &= ~(OPf_REF|OPf_SPECIAL);
            return left;
        }
        curop = list(force_list(left));
        o = newBINOP(OP_AASSIGN, flags, list(force_list(right)), curop);
        o->op_private = (U8)(0 | (flags >> 8));
        for (curop = ((LISTOP*)curop)->op_first;
             curop; curop = curop->op_sibling)
        {
            if (curop->op_type == OP_RV2HV &&
                ((UNOP*)curop)->op_first->op_type != OP_GV) {
                o->op_private |= OPpASSIGN_HASH;
                break;
            }
        }

        /* PL_generation sorcery:
         * an assignment like ($a,$b) = ($c,$d) is easier than
         * ($a,$b) = ($c,$a), since there is no need for temporary vars.
         * To detect whether there are common vars, the global var
         * PL_generation is incremented for each assign op we compile.
         * Then, while compiling the assign op, we run through all the
         * variables on both sides of the assignment, setting a spare slot
         * in each of them to PL_generation. If any of them already have
         * that value, we know we've got commonality.  We could use a
         * single bit marker, but then we'd have to make 2 passes, first
         * to clear the flag, then to test and set it.  To find somewhere
         * to store these values, evil chicanery is done with SvCUR().
         */
        
        if (!(left->op_private & OPpLVAL_INTRO)) {
            OP *lastop = o;
            PL_generation++;
            for (curop = LINKLIST(o); curop != o; curop = LINKLIST(curop)) {
                if (PL_opargs[curop->op_type] & OA_DANGEROUS) {
                    if (curop->op_type == OP_GV) {
                        GV *gv = cGVOPx_gv(curop);
                        if (gv == PL_defgv || (int)SvCUR(gv) == PL_generation)
                            break;
                        SvCUR(gv) = PL_generation;
                    }
                    else if (curop->op_type == OP_PADSV ||
                             curop->op_type == OP_PADAV ||
                             curop->op_type == OP_PADHV ||
                             curop->op_type == OP_PADANY)
                    {
                        if ((int)PAD_COMPNAME_GEN(curop->op_targ)
                                                    == PL_generation)
                            break;
                        PAD_COMPNAME_GEN(curop->op_targ)
                                                        = PL_generation;

                    }
                    else if (curop->op_type == OP_RV2CV)
                        break;
                    else if (curop->op_type == OP_RV2SV ||
                             curop->op_type == OP_RV2AV ||
                             curop->op_type == OP_RV2HV ||
                             curop->op_type == OP_RV2GV) {
                        if (lastop->op_type != OP_GV)   /* funny deref? */
                            break;
                    }
                    else if (curop->op_type == OP_PUSHRE) {
                        if (((PMOP*)curop)->op_pmreplroot) {
#ifdef USE_ITHREADS
                            GV *gv = (GV*)PAD_SVl(INT2PTR(PADOFFSET,
                                        ((PMOP*)curop)->op_pmreplroot));
#else
                            GV *gv = (GV*)((PMOP*)curop)->op_pmreplroot;
#endif
                            if (gv == PL_defgv || (int)SvCUR(gv) == PL_generation)
                                break;
                            SvCUR(gv) = PL_generation;
                        }
                    }
                    else
                        break;
                }
                lastop = curop;
            }
            if (curop != o)
                o->op_private |= OPpASSIGN_COMMON;
        }
        if (right && right->op_type == OP_SPLIT) {
            OP* tmpop;
            if ((tmpop = ((LISTOP*)right)->op_first) &&
                tmpop->op_type == OP_PUSHRE)
            {
                PMOP *pm = (PMOP*)tmpop;
                if (left->op_type == OP_RV2AV &&
                    !(left->op_private & OPpLVAL_INTRO) &&
                    !(o->op_private & OPpASSIGN_COMMON) )
                {
                    tmpop = ((UNOP*)left)->op_first;
                    if (tmpop->op_type == OP_GV && !pm->op_pmreplroot) {
#ifdef USE_ITHREADS
                        pm->op_pmreplroot = INT2PTR(OP*, cPADOPx(tmpop)->op_padix);
                        cPADOPx(tmpop)->op_padix = 0;   /* steal it */
#else
                        pm->op_pmreplroot = (OP*)cSVOPx(tmpop)->op_sv;
                        cSVOPx(tmpop)->op_sv = Nullsv;  /* steal it */
#endif
                        pm->op_pmflags |= PMf_ONCE;
                        tmpop = cUNOPo->op_first;       /* to list (nulled) */
                        tmpop = ((UNOP*)tmpop)->op_first; /* to pushmark */
                        tmpop->op_sibling = Nullop;     /* don't free split */
                        right->op_next = tmpop->op_next;  /* fix starting loc */
                        op_free(o);                     /* blow off assign */
                        right->op_flags &= ~OPf_WANT;
                                /* "I don't know and I don't care." */
                        return right;
                    }
                }
                else {
                   if (PL_modcount < RETURN_UNLIMITED_NUMBER &&
                      ((LISTOP*)right)->op_last->op_type == OP_CONST)
                    {
                        SV *sv = ((SVOP*)((LISTOP*)right)->op_last)->op_sv;
                        if (SvIVX(sv) == 0)
                            sv_setiv(sv, PL_modcount+1);
                    }
                }
            }
        }
        return o;
    }
    if (!right)
        right = newOP(OP_UNDEF, 0);
    if (right->op_type == OP_READLINE) {
        right->op_flags |= OPf_STACKED;
        return newBINOP(OP_NULL, flags, mod(scalar(left), OP_SASSIGN), scalar(right));
    }
    else {
        PL_eval_start = right;  /* Grandfathering $[ assignment here.  Bletch.*/
        o = newBINOP(OP_SASSIGN, flags,
            scalar(right), mod(scalar(left), OP_SASSIGN) );
        if (PL_eval_start)
            PL_eval_start = 0;
        else {
            op_free(o);
            return Nullop;
        }
    }
    return o;
}

OP *
Perl_newSTATEOP(pTHX_ I32 flags, char *label, OP *o)
{
    U32 seq = intro_my();
    register COP *cop;

    NewOp(1101, cop, 1, COP);
    if (PERLDB_LINE && CopLINE(PL_curcop) && PL_curstash != PL_debstash) {
        cop->op_type = OP_DBSTATE;
        cop->op_ppaddr = PL_ppaddr[ OP_DBSTATE ];
    }
    else {
        cop->op_type = OP_NEXTSTATE;
        cop->op_ppaddr = PL_ppaddr[ OP_NEXTSTATE ];
    }
    cop->op_flags = (U8)flags;
    cop->op_private = (U8)(PL_hints & HINT_PRIVATE_MASK);
#ifdef NATIVE_HINTS
    cop->op_private |= NATIVE_HINTS;
#endif
    PL_compiling.op_private = cop->op_private;
    cop->op_next = (OP*)cop;

    if (label) {
        cop->cop_label = label;
        PL_hints |= HINT_BLOCK_SCOPE;
    }
    cop->cop_seq = seq;
    cop->cop_arybase = PL_curcop->cop_arybase;
    if (specialWARN(PL_curcop->cop_warnings))
        cop->cop_warnings = PL_curcop->cop_warnings ;
    else
        cop->cop_warnings = newSVsv(PL_curcop->cop_warnings) ;
    if (specialCopIO(PL_curcop->cop_io))
        cop->cop_io = PL_curcop->cop_io;
    else
        cop->cop_io = newSVsv(PL_curcop->cop_io) ;


    if (PL_copline == NOLINE)
        CopLINE_set(cop, CopLINE(PL_curcop));
    else {
        CopLINE_set(cop, PL_copline);
        PL_copline = NOLINE;
    }
#ifdef USE_ITHREADS
    CopFILE_set(cop, CopFILE(PL_curcop));       /* XXX share in a pvtable? */
#else
    CopFILEGV_set(cop, CopFILEGV(PL_curcop));
#endif
    CopSTASH_set(cop, PL_curstash);

    if (PERLDB_LINE && PL_curstash != PL_debstash) {
        SV **svp = av_fetch(CopFILEAV(PL_curcop), (I32)CopLINE(cop), FALSE);
        if (svp && *svp != &PL_sv_undef ) {
           (void)SvIOK_on(*svp);
            SvIVX(*svp) = PTR2IV(cop);
        }
    }

    return prepend_elem(OP_LINESEQ, (OP*)cop, o);
}


OP *
Perl_newLOGOP(pTHX_ I32 type, I32 flags, OP *first, OP *other)
{
    return new_logop(type, flags, &first, &other);
}

STATIC OP *
S_new_logop(pTHX_ I32 type, I32 flags, OP** firstp, OP** otherp)
{
    LOGOP *logop;
    OP *o;
    OP *first = *firstp;
    OP *other = *otherp;

    if (type == OP_XOR)         /* Not short circuit, but here by precedence. */
        return newBINOP(type, flags, scalar(first), scalar(other));

    scalarboolean(first);
    /* optimize "!a && b" to "a || b", and "!a || b" to "a && b" */
    if (first->op_type == OP_NOT && (first->op_flags & OPf_SPECIAL)) {
        if (type == OP_AND || type == OP_OR) {
            if (type == OP_AND)
                type = OP_OR;
            else
                type = OP_AND;
            o = first;
            first = *firstp = cUNOPo->op_first;
            if (o->op_next)
                first->op_next = o->op_next;
            cUNOPo->op_first = Nullop;
            op_free(o);
        }
    }
    if (first->op_type == OP_CONST) {
        if (first->op_private & OPpCONST_STRICT)
            no_bareword_allowed(first);
        else if (ckWARN(WARN_BAREWORD) && (first->op_private & OPpCONST_BARE))
                Perl_warner(aTHX_ packWARN(WARN_BAREWORD), "Bareword found in conditional");
        if ((type == OP_AND) == (SvTRUE(((SVOP*)first)->op_sv))) {
            op_free(first);
            *firstp = Nullop;
            if (other->op_type == OP_CONST)
                other->op_private |= OPpCONST_SHORTCIRCUIT;
            return other;
        }
        else {
            op_free(other);
            *otherp = Nullop;
            if (first->op_type == OP_CONST)
                first->op_private |= OPpCONST_SHORTCIRCUIT;
            return first;
        }
    }
    else if (ckWARN(WARN_MISC) && (first->op_flags & OPf_KIDS)) {
        OP *k1 = ((UNOP*)first)->op_first;
        OP *k2 = k1->op_sibling;
        OPCODE warnop = 0;
        switch (first->op_type)
        {
        case OP_NULL:
            if (k2 && k2->op_type == OP_READLINE
                  && (k2->op_flags & OPf_STACKED)
                  && ((k1->op_flags & OPf_WANT) == OPf_WANT_SCALAR))
            {
                warnop = k2->op_type;
            }
            break;

        case OP_SASSIGN:
            if (k1->op_type == OP_READDIR
                  || k1->op_type == OP_GLOB
                  || (k1->op_type == OP_NULL && k1->op_targ == OP_GLOB)
                  || k1->op_type == OP_EACH)
            {
                warnop = ((k1->op_type == OP_NULL)
                          ? (OPCODE)k1->op_targ : k1->op_type);
            }
            break;
        }
        if (warnop) {
            line_t oldline = CopLINE(PL_curcop);
            CopLINE_set(PL_curcop, PL_copline);
            Perl_warner(aTHX_ packWARN(WARN_MISC),
                 "Value of %s%s can be \"0\"; test with defined()",
                 PL_op_desc[warnop],
                 ((warnop == OP_READLINE || warnop == OP_GLOB)
                  ? " construct" : "() operator"));
            CopLINE_set(PL_curcop, oldline);
        }
    }

    if (!other)
        return first;

    if (type == OP_ANDASSIGN || type == OP_ORASSIGN)
        other->op_private |= OPpASSIGN_BACKWARDS;  /* other is an OP_SASSIGN */

    NewOp(1101, logop, 1, LOGOP);

    logop->op_type = (OPCODE)type;
    logop->op_ppaddr = PL_ppaddr[type];
    logop->op_first = first;
    logop->op_flags = flags | OPf_KIDS;
    logop->op_other = LINKLIST(other);
    logop->op_private = (U8)(1 | (flags >> 8));

    /* establish postfix order */
    logop->op_next = LINKLIST(first);
    first->op_next = (OP*)logop;
    first->op_sibling = other;

    CHECKOP(type,logop);

    o = newUNOP(OP_NULL, 0, (OP*)logop);
    other->op_next = o;

    return o;
}

OP *
Perl_newCONDOP(pTHX_ I32 flags, OP *first, OP *trueop, OP *falseop)
{
    LOGOP *logop;
    OP *start;
    OP *o;

    if (!falseop)
        return newLOGOP(OP_AND, 0, first, trueop);
    if (!trueop)
        return newLOGOP(OP_OR, 0, first, falseop);

    scalarboolean(first);
    if (first->op_type == OP_CONST) {
        if (first->op_private & OPpCONST_BARE &&
           first->op_private & OPpCONST_STRICT) {
           no_bareword_allowed(first);
       }
        if (SvTRUE(((SVOP*)first)->op_sv)) {
            op_free(first);
            op_free(falseop);
            return trueop;
        }
        else {
            op_free(first);
            op_free(trueop);
            return falseop;
        }
    }
    NewOp(1101, logop, 1, LOGOP);
    logop->op_type = OP_COND_EXPR;
    logop->op_ppaddr = PL_ppaddr[OP_COND_EXPR];
    logop->op_first = first;
    logop->op_flags = flags | OPf_KIDS;
    logop->op_private = (U8)(1 | (flags >> 8));
    logop->op_other = LINKLIST(trueop);
    logop->op_next = LINKLIST(falseop);

    CHECKOP(OP_COND_EXPR, /* that's logop->op_type */
            logop);

    /* establish postfix order */
    start = LINKLIST(first);
    first->op_next = (OP*)logop;

    first->op_sibling = trueop;
    trueop->op_sibling = falseop;
    o = newUNOP(OP_NULL, 0, (OP*)logop);

    trueop->op_next = falseop->op_next = o;

    o->op_next = start;
    return o;
}

OP *
Perl_newRANGE(pTHX_ I32 flags, OP *left, OP *right)
{
    LOGOP *range;
    OP *flip;
    OP *flop;
    OP *leftstart;
    OP *o;

    NewOp(1101, range, 1, LOGOP);

    range->op_type = OP_RANGE;
    range->op_ppaddr = PL_ppaddr[OP_RANGE];
    range->op_first = left;
    range->op_flags = OPf_KIDS;
    leftstart = LINKLIST(left);
    range->op_other = LINKLIST(right);
    range->op_private = (U8)(1 | (flags >> 8));

    left->op_sibling = right;

    range->op_next = (OP*)range;
    flip = newUNOP(OP_FLIP, flags, (OP*)range);
    flop = newUNOP(OP_FLOP, 0, flip);
    o = newUNOP(OP_NULL, 0, flop);
    linklist(flop);
    range->op_next = leftstart;

    left->op_next = flip;
    right->op_next = flop;

    range->op_targ = pad_alloc(OP_RANGE, SVs_PADMY);
    sv_upgrade(PAD_SV(range->op_targ), SVt_PVNV);
    flip->op_targ = pad_alloc(OP_RANGE, SVs_PADMY);
    sv_upgrade(PAD_SV(flip->op_targ), SVt_PVNV);

    flip->op_private =  left->op_type == OP_CONST ? OPpFLIP_LINENUM : 0;
    flop->op_private = right->op_type == OP_CONST ? OPpFLIP_LINENUM : 0;

    flip->op_next = o;
    if (!flip->op_private || !flop->op_private)
        linklist(o);            /* blow off optimizer unless constant */

    return o;
}

OP *
Perl_newLOOPOP(pTHX_ I32 flags, I32 debuggable, OP *expr, OP *block)
{
    OP* listop;
    OP* o;
    int once = block && block->op_flags & OPf_SPECIAL &&
      (block->op_type == OP_ENTERSUB || block->op_type == OP_NULL);

    if (expr) {
        if (once && expr->op_type == OP_CONST && !SvTRUE(((SVOP*)expr)->op_sv))
            return block;       /* do {} while 0 does once */
        if (expr->op_type == OP_READLINE || expr->op_type == OP_GLOB
            || (expr->op_type == OP_NULL && expr->op_targ == OP_GLOB)) {
            expr = newUNOP(OP_DEFINED, 0,
                newASSIGNOP(0, newDEFSVOP(), 0, expr) );
        } else if (expr->op_flags & OPf_KIDS) {
            OP *k1 = ((UNOP*)expr)->op_first;
            OP *k2 = (k1) ? k1->op_sibling : NULL;
            switch (expr->op_type) {
              case OP_NULL:
                if (k2 && k2->op_type == OP_READLINE
                      && (k2->op_flags & OPf_STACKED)
                      && ((k1->op_flags & OPf_WANT) == OPf_WANT_SCALAR))
                    expr = newUNOP(OP_DEFINED, 0, expr);
                break;

              case OP_SASSIGN:
                if (k1->op_type == OP_READDIR
                      || k1->op_type == OP_GLOB
                      || (k1->op_type == OP_NULL && k1->op_targ == OP_GLOB)
                      || k1->op_type == OP_EACH)
                    expr = newUNOP(OP_DEFINED, 0, expr);
                break;
            }
        }
    }

    /* if block is null, the next append_elem() would put UNSTACK, a scalar
     * op, in listop. This is wrong. [perl #27024] */
    if (!block)
        block = newOP(OP_NULL, 0);
    listop = append_elem(OP_LINESEQ, block, newOP(OP_UNSTACK, 0));
    o = new_logop(OP_AND, 0, &expr, &listop);

    if (listop)
        ((LISTOP*)listop)->op_last->op_next = LINKLIST(o);

    if (once && o != listop)
        o->op_next = ((LOGOP*)cUNOPo->op_first)->op_other;

    if (o == listop)
        o = newUNOP(OP_NULL, 0, o);     /* or do {} while 1 loses outer block */

    o->op_flags |= flags;
    o = scope(o);
    o->op_flags |= OPf_SPECIAL; /* suppress POPBLOCK curpm restoration*/
    return o;
}

OP *
Perl_newWHILEOP(pTHX_ I32 flags, I32 debuggable, LOOP *loop, I32 whileline, OP *expr, OP *block, OP *cont)
{
    OP *redo;
    OP *next = 0;
    OP *listop;
    OP *o;
    U8 loopflags = 0;

    if (expr && (expr->op_type == OP_READLINE || expr->op_type == OP_GLOB
                 || (expr->op_type == OP_NULL && expr->op_targ == OP_GLOB))) {
        expr = newUNOP(OP_DEFINED, 0,
            newASSIGNOP(0, newDEFSVOP(), 0, expr) );
    } else if (expr && (expr->op_flags & OPf_KIDS)) {
        OP *k1 = ((UNOP*)expr)->op_first;
        OP *k2 = (k1) ? k1->op_sibling : NULL;
        switch (expr->op_type) {
          case OP_NULL:
            if (k2 && k2->op_type == OP_READLINE
                  && (k2->op_flags & OPf_STACKED)
                  && ((k1->op_flags & OPf_WANT) == OPf_WANT_SCALAR))
                expr = newUNOP(OP_DEFINED, 0, expr);
            break;

          case OP_SASSIGN:
            if (k1->op_type == OP_READDIR
                  || k1->op_type == OP_GLOB
                  || (k1->op_type == OP_NULL && k1->op_targ == OP_GLOB)
                  || k1->op_type == OP_EACH)
                expr = newUNOP(OP_DEFINED, 0, expr);
            break;
        }
    }

    if (!block)
        block = newOP(OP_NULL, 0);
    else if (cont) {
        block = scope(block);
    }

    if (cont) {
        next = LINKLIST(cont);
    }
    if (expr) {
        OP *unstack = newOP(OP_UNSTACK, 0);
        if (!next)
            next = unstack;
        cont = append_elem(OP_LINESEQ, cont, unstack);
    }

    listop = append_list(OP_LINESEQ, (LISTOP*)block, (LISTOP*)cont);
    redo = LINKLIST(listop);

    if (expr) {
        PL_copline = (line_t)whileline;
        scalar(listop);
        o = new_logop(OP_AND, 0, &expr, &listop);
        if (o == expr && o->op_type == OP_CONST && !SvTRUE(cSVOPo->op_sv)) {
            op_free(expr);              /* oops, it's a while (0) */
            op_free((OP*)loop);
            return Nullop;              /* listop already freed by new_logop */
        }
        if (listop)
            ((LISTOP*)listop)->op_last->op_next =
                (o == listop ? redo : LINKLIST(o));
    }
    else
        o = listop;

    if (!loop) {
        NewOp(1101,loop,1,LOOP);
        loop->op_type = OP_ENTERLOOP;
        loop->op_ppaddr = PL_ppaddr[OP_ENTERLOOP];
        loop->op_private = 0;
        loop->op_next = (OP*)loop;
    }

    o = newBINOP(OP_LEAVELOOP, 0, (OP*)loop, o);

    loop->op_redoop = redo;
    loop->op_lastop = o;
    o->op_private |= loopflags;

    if (next)
        loop->op_nextop = next;
    else
        loop->op_nextop = o;

    o->op_flags |= flags;
    o->op_private |= (flags >> 8);
    return o;
}

OP *
Perl_newFOROP(pTHX_ I32 flags,char *label,line_t forline,OP *sv,OP *expr,OP *block,OP *cont)
{
    LOOP *loop;
    OP *wop;
    PADOFFSET padoff = 0;
    I32 iterflags = 0;
    I32 iterpflags = 0;

    if (sv) {
        if (sv->op_type == OP_RV2SV) {  /* symbol table variable */
            iterpflags = sv->op_private & OPpOUR_INTRO; /* for our $x () */
            sv->op_type = OP_RV2GV;
            sv->op_ppaddr = PL_ppaddr[OP_RV2GV];
        }
        else if (sv->op_type == OP_PADSV) { /* private variable */
            iterpflags = sv->op_private & OPpLVAL_INTRO; /* for my $x () */
            padoff = sv->op_targ;
            sv->op_targ = 0;
            op_free(sv);
            sv = Nullop;
        }
        else if (sv->op_type == OP_THREADSV) { /* per-thread variable */
            padoff = sv->op_targ;
            sv->op_targ = 0;
            iterflags |= OPf_SPECIAL;
            op_free(sv);
            sv = Nullop;
        }
        else
            Perl_croak(aTHX_ "Can't use %s for loop variable", PL_op_desc[sv->op_type]);
    }
    else {
#ifdef USE_5005THREADS
        padoff = find_threadsv("_");
        iterflags |= OPf_SPECIAL;
#else
        sv = newGVOP(OP_GV, 0, PL_defgv);
#endif
    }
    if (expr->op_type == OP_RV2AV || expr->op_type == OP_PADAV) {
        expr = mod(force_list(scalar(ref(expr, OP_ITER))), OP_GREPSTART);
        iterflags |= OPf_STACKED;
    }
    else if (expr->op_type == OP_NULL &&
             (expr->op_flags & OPf_KIDS) &&
             ((BINOP*)expr)->op_first->op_type == OP_FLOP)
    {
        /* Basically turn for($x..$y) into the same as for($x,$y), but we
         * set the STACKED flag to indicate that these values are to be
         * treated as min/max values by 'pp_iterinit'.
         */
        UNOP* flip = (UNOP*)((UNOP*)((BINOP*)expr)->op_first)->op_first;
        LOGOP* range = (LOGOP*) flip->op_first;
        OP* left  = range->op_first;
        OP* right = left->op_sibling;
        LISTOP* listop;

        range->op_flags &= ~OPf_KIDS;
        range->op_first = Nullop;

        listop = (LISTOP*)newLISTOP(OP_LIST, 0, left, right);
        listop->op_first->op_next = range->op_next;
        left->op_next = range->op_other;
        right->op_next = (OP*)listop;
        listop->op_next = listop->op_first;

        op_free(expr);
        expr = (OP*)(listop);
        op_null(expr);
        iterflags |= OPf_STACKED;
    }
    else {
        expr = mod(force_list(expr), OP_GREPSTART);
    }

    loop = (LOOP*)list(convert(OP_ENTERITER, iterflags,
                               append_elem(OP_LIST, expr, scalar(sv))));
    assert(!loop->op_next);
    /* for my  $x () sets OPpLVAL_INTRO;
     * for our $x () sets OPpOUR_INTRO; both only used by Deparse.pm */
    loop->op_private = (U8)iterpflags;
#ifdef PL_OP_SLAB_ALLOC
    {
        LOOP *tmp;
        NewOp(1234,tmp,1,LOOP);
        Copy(loop,tmp,1,LISTOP);
        FreeOp(loop);
        loop = tmp;
    }
#else
    Renew(loop, 1, LOOP);
#endif
    loop->op_targ = padoff;
    wop = newWHILEOP(flags, 1, loop, forline, newOP(OP_ITER, 0), block, cont);
    PL_copline = forline;
    return newSTATEOP(0, label, wop);
}

OP*
Perl_newLOOPEX(pTHX_ I32 type, OP *label)
{
    OP *o;
    STRLEN n_a;

    if (type != OP_GOTO || label->op_type == OP_CONST) {
        /* "last()" means "last" */
        if (label->op_type == OP_STUB && (label->op_flags & OPf_PARENS))
            o = newOP(type, OPf_SPECIAL);
        else {
            o = newPVOP(type, 0, savepv(label->op_type == OP_CONST
                                        ? SvPVx(((SVOP*)label)->op_sv, n_a)
                                        : ""));
        }
        op_free(label);
    }
    else {
        /* Check whether it's going to be a goto &function */
        if (label->op_type == OP_ENTERSUB
                && !(label->op_flags & OPf_STACKED))
            label = newUNOP(OP_REFGEN, 0, mod(label, OP_REFGEN));
        o = newUNOP(type, OPf_STACKED, label);
    }
    PL_hints |= HINT_BLOCK_SCOPE;
    return o;
}

/*
=for apidoc cv_undef

Clear out all the active components of a CV. This can happen either
by an explicit C<undef &foo>, or by the reference count going to zero.
In the former case, we keep the CvOUTSIDE pointer, so that any anonymous
children can still follow the full lexical scope chain.

=cut
*/

void
Perl_cv_undef(pTHX_ CV *cv)
{
#ifdef USE_5005THREADS
    if (CvMUTEXP(cv)) {
        MUTEX_DESTROY(CvMUTEXP(cv));
        Safefree(CvMUTEXP(cv));
        CvMUTEXP(cv) = 0;
    }
#endif /* USE_5005THREADS */

#ifdef USE_ITHREADS
    if (CvFILE(cv) && !CvXSUB(cv)) {
        /* for XSUBs CvFILE point directly to static memory; __FILE__ */
        Safefree(CvFILE(cv));
    }
    CvFILE(cv) = 0;
#endif

    if (!CvXSUB(cv) && CvROOT(cv)) {
#ifdef USE_5005THREADS
        if (CvDEPTH(cv) || (CvOWNER(cv) && CvOWNER(cv) != thr))
            Perl_croak(aTHX_ "Can't undef active subroutine");
#else
        if (CvDEPTH(cv))
            Perl_croak(aTHX_ "Can't undef active subroutine");
#endif /* USE_5005THREADS */
        ENTER;

        PAD_SAVE_SETNULLPAD();

        op_free(CvROOT(cv));
        CvROOT(cv) = Nullop;
        LEAVE;
    }
    SvPOK_off((SV*)cv);         /* forget prototype */
    CvGV(cv) = Nullgv;

    pad_undef(cv);

    /* remove CvOUTSIDE unless this is an undef rather than a free */
    if (!SvREFCNT(cv) && CvOUTSIDE(cv)) {
        if (!CvWEAKOUTSIDE(cv))
            SvREFCNT_dec(CvOUTSIDE(cv));
        CvOUTSIDE(cv) = Nullcv;
    }
    if (CvCONST(cv)) {
        SvREFCNT_dec((SV*)CvXSUBANY(cv).any_ptr);
        CvCONST_off(cv);
    }
    if (CvXSUB(cv)) {
        CvXSUB(cv) = 0;
    }
    /* delete all flags except WEAKOUTSIDE */
    CvFLAGS(cv) &= CVf_WEAKOUTSIDE;
}

void
Perl_cv_ckproto(pTHX_ CV *cv, GV *gv, char *p)
{
    if (((!p != !SvPOK(cv)) || (p && strNE(p, SvPVX(cv)))) && ckWARN_d(WARN_PROTOTYPE)) {
        SV* msg = sv_newmortal();
        SV* name = Nullsv;

        if (gv)
            gv_efullname3(name = sv_newmortal(), gv, Nullch);
        sv_setpv(msg, "Prototype mismatch:");
        if (name)
            Perl_sv_catpvf(aTHX_ msg, " sub %"SVf, name);
        if (SvPOK(cv))
            Perl_sv_catpvf(aTHX_ msg, " (%"SVf")", (SV *)cv);
        else
            Perl_sv_catpv(aTHX_ msg, ": none");
        sv_catpv(msg, " vs ");
        if (p)
            Perl_sv_catpvf(aTHX_ msg, "(%s)", p);
        else
            sv_catpv(msg, "none");
        Perl_warner(aTHX_ packWARN(WARN_PROTOTYPE), "%"SVf, msg);
    }
}

static void const_sv_xsub(pTHX_ CV* cv);

/*

=head1 Optree Manipulation Functions

=for apidoc cv_const_sv

If C<cv> is a constant sub eligible for inlining. returns the constant
value returned by the sub.  Otherwise, returns NULL.

Constant subs can be created with C<newCONSTSUB> or as described in
L<perlsub/"Constant Functions">.

=cut
*/
SV *
Perl_cv_const_sv(pTHX_ CV *cv)
{
    if (!cv || !CvCONST(cv))
        return Nullsv;
    return (SV*)CvXSUBANY(cv).any_ptr;
}

SV *
Perl_op_const_sv(pTHX_ OP *o, CV *cv)
{
    SV *sv = Nullsv;

    if (!o)
        return Nullsv;

    if (o->op_type == OP_LINESEQ && cLISTOPo->op_first)
        o = cLISTOPo->op_first->op_sibling;

    for (; o; o = o->op_next) {
        OPCODE type = o->op_type;

        if (sv && o->op_next == o)
            return sv;
        if (o->op_next != o) {
            if (type == OP_NEXTSTATE || type == OP_NULL || type == OP_PUSHMARK)
                continue;
            if (type == OP_DBSTATE)
                continue;
        }
        if (type == OP_LEAVESUB || type == OP_RETURN)
            break;
        if (sv)
            return Nullsv;
        if (type == OP_CONST && cSVOPo->op_sv)
            sv = cSVOPo->op_sv;
        else if ((type == OP_PADSV || type == OP_CONST) && cv) {
            sv = PAD_BASE_SV(CvPADLIST(cv), o->op_targ);
            if (!sv)
                return Nullsv;
            if (CvCONST(cv)) {
                /* We get here only from cv_clone2() while creating a closure.
                   Copy the const value here instead of in cv_clone2 so that
                   SvREADONLY_on doesn't lead to problems when leaving
                   scope.
                */
                sv = newSVsv(sv);
            }
            if (!SvREADONLY(sv) && SvREFCNT(sv) > 1)
                return Nullsv;
        }
        else
            return Nullsv;
    }
    if (sv)
        SvREADONLY_on(sv);
    return sv;
}

void
Perl_newMYSUB(pTHX_ I32 floor, OP *o, OP *proto, OP *attrs, OP *block)
{
    if (o)
        SAVEFREEOP(o);
    if (proto)
        SAVEFREEOP(proto);
    if (attrs)
        SAVEFREEOP(attrs);
    if (block)
        SAVEFREEOP(block);
    Perl_croak(aTHX_ "\"my sub\" not yet implemented");
}

CV *
Perl_newSUB(pTHX_ I32 floor, OP *o, OP *proto, OP *block)
{
    return Perl_newATTRSUB(aTHX_ floor, o, proto, Nullop, block);
}

CV *
Perl_newATTRSUB(pTHX_ I32 floor, OP *o, OP *proto, OP *attrs, OP *block)
{
    STRLEN n_a;
    char *name;
    char *aname;
    GV *gv;
    char *ps;
    register CV *cv=0;
    SV *const_sv;

    name = o ? SvPVx(cSVOPo->op_sv, n_a) : Nullch;

    if (proto) {
        assert(proto->op_type == OP_CONST);
        ps = SvPVx(((SVOP*)proto)->op_sv, n_a);
    }
    else
        ps = Nullch;

    if (!name && PERLDB_NAMEANON && CopLINE(PL_curcop)) {
        SV *sv = sv_newmortal();
        Perl_sv_setpvf(aTHX_ sv, "%s[%s:%"IVdf"]",
                       PL_curstash ? "__ANON__" : "__ANON__::__ANON__",
                       CopFILE(PL_curcop), (IV)CopLINE(PL_curcop));
        aname = SvPVX(sv);
    }
    else
        aname = Nullch;
    gv = gv_fetchpv(name ? name : (aname ? aname : 
                    (PL_curstash ? "__ANON__" : "__ANON__::__ANON__")),
                    GV_ADDMULTI | ((block || attrs) ? 0 : GV_NOINIT),
                    SVt_PVCV);

    if (o)
        SAVEFREEOP(o);
    if (proto)
        SAVEFREEOP(proto);
    if (attrs)
        SAVEFREEOP(attrs);

    if (SvTYPE(gv) != SVt_PVGV) {       /* Maybe prototype now, and had at
                                           maximum a prototype before. */
        if (SvTYPE(gv) > SVt_NULL) {
            if (!SvPOK((SV*)gv) && !(SvIOK((SV*)gv) && SvIVX((SV*)gv) == -1)
                && ckWARN_d(WARN_PROTOTYPE))
            {
                Perl_warner(aTHX_ packWARN(WARN_PROTOTYPE), "Runaway prototype");
            }
            cv_ckproto((CV*)gv, NULL, ps);
        }
        if (ps)
            sv_setpv((SV*)gv, ps);
        else
            sv_setiv((SV*)gv, -1);
        SvREFCNT_dec(PL_compcv);
        cv = PL_compcv = NULL;
        PL_sub_generation++;
        goto done;
    }

    cv = (!name || GvCVGEN(gv)) ? Nullcv : GvCV(gv);

#ifdef GV_UNIQUE_CHECK
    if (cv && GvUNIQUE(gv) && SvREADONLY(cv)) {
        Perl_croak(aTHX_ "Can't define subroutine %s (GV is unique)", name);
    }
#endif

    if (!block || !ps || *ps || attrs)
        const_sv = Nullsv;
    else
        const_sv = op_const_sv(block, Nullcv);

    if (cv) {
        bool exists = CvROOT(cv) || CvXSUB(cv);

#ifdef GV_UNIQUE_CHECK
        if (exists && GvUNIQUE(gv)) {
            Perl_croak(aTHX_ "Can't redefine unique subroutine %s", name);
        }
#endif

        /* if the subroutine doesn't exist and wasn't pre-declared
         * with a prototype, assume it will be AUTOLOADed,
         * skipping the prototype check
         */
        if (exists || SvPOK(cv))
            cv_ckproto(cv, gv, ps);
        /* already defined (or promised)? */
        if (exists || GvASSUMECV(gv)) {
            if (!block && !attrs) {
                if (CvFLAGS(PL_compcv)) {
                    /* might have had built-in attrs applied */
                    CvFLAGS(cv) |= (CvFLAGS(PL_compcv) & CVf_BUILTIN_ATTRS);
                }
                /* just a "sub foo;" when &foo is already defined */
                SAVEFREESV(PL_compcv);
                goto done;
            }
            /* ahem, death to those who redefine active sort subs */
            if (PL_curstackinfo->si_type == PERLSI_SORT && PL_sortcop == CvSTART(cv))
                Perl_croak(aTHX_ "Can't redefine active sort subroutine %s", name);
            if (block) {
                if (ckWARN(WARN_REDEFINE)
                    || (CvCONST(cv)
                        && (!const_sv || sv_cmp(cv_const_sv(cv), const_sv))))
                {
                    line_t oldline = CopLINE(PL_curcop);
                    if (PL_copline != NOLINE)
                        CopLINE_set(PL_curcop, PL_copline);
                    Perl_warner(aTHX_ packWARN(WARN_REDEFINE),
                        CvCONST(cv) ? "Constant subroutine %s redefined"
                                    : "Subroutine %s redefined", name);
                    CopLINE_set(PL_curcop, oldline);
                }
                SvREFCNT_dec(cv);
                cv = Nullcv;
            }
        }
    }
    if (const_sv) {
        SvREFCNT_inc(const_sv);
        if (cv) {
            assert(!CvROOT(cv) && !CvCONST(cv));
            sv_setpv((SV*)cv, "");  /* prototype is "" */
            CvXSUBANY(cv).any_ptr = const_sv;
            CvXSUB(cv) = const_sv_xsub;
            CvCONST_on(cv);
        }
        else {
            GvCV(gv) = Nullcv;
            cv = newCONSTSUB(NULL, name, const_sv);
        }
        op_free(block);
        SvREFCNT_dec(PL_compcv);
        PL_compcv = NULL;
        PL_sub_generation++;
        goto done;
    }
    if (attrs) {
        HV *stash;
        SV *rcv;

        /* Need to do a C<use attributes $stash_of_cv,\&cv,@attrs>
         * before we clobber PL_compcv.
         */
        if (cv && !block) {
            rcv = (SV*)cv;
            /* Might have had built-in attributes applied -- propagate them. */
            CvFLAGS(cv) |= (CvFLAGS(PL_compcv) & CVf_BUILTIN_ATTRS);
            if (CvGV(cv) && GvSTASH(CvGV(cv)))
                stash = GvSTASH(CvGV(cv));
            else if (CvSTASH(cv))
                stash = CvSTASH(cv);
            else
                stash = PL_curstash;
        }
        else {
            /* possibly about to re-define existing subr -- ignore old cv */
            rcv = (SV*)PL_compcv;
            if (name && GvSTASH(gv))
                stash = GvSTASH(gv);
            else
                stash = PL_curstash;
        }
        apply_attrs(stash, rcv, attrs, FALSE);
    }
    if (cv) {                           /* must reuse cv if autoloaded */
        if (!block) {
            /* got here with just attrs -- work done, so bug out */
            SAVEFREESV(PL_compcv);
            goto done;
        }
        /* transfer PL_compcv to cv */
        cv_undef(cv);
        CvFLAGS(cv) = CvFLAGS(PL_compcv);
        if (!CvWEAKOUTSIDE(cv))
            SvREFCNT_dec(CvOUTSIDE(cv));
        CvOUTSIDE(cv) = CvOUTSIDE(PL_compcv);
        CvOUTSIDE_SEQ(cv) = CvOUTSIDE_SEQ(PL_compcv);
        CvOUTSIDE(PL_compcv) = 0;
        CvPADLIST(cv) = CvPADLIST(PL_compcv);
        CvPADLIST(PL_compcv) = 0;
        /* inner references to PL_compcv must be fixed up ... */
        pad_fixup_inner_anons(CvPADLIST(cv), PL_compcv, cv);
        /* ... before we throw it away */
        SvREFCNT_dec(PL_compcv);
        if (PERLDB_INTER)/* Advice debugger on the new sub. */
          ++PL_sub_generation;
    }
    else {
        cv = PL_compcv;
        if (name) {
            GvCV(gv) = cv;
            GvCVGEN(gv) = 0;
            PL_sub_generation++;
        }
    }
    CvGV(cv) = gv;
    CvFILE_set_from_cop(cv, PL_curcop);
    CvSTASH(cv) = PL_curstash;
#ifdef USE_5005THREADS
    CvOWNER(cv) = 0;
    if (!CvMUTEXP(cv)) {
        New(666, CvMUTEXP(cv), 1, perl_mutex);
        MUTEX_INIT(CvMUTEXP(cv));
    }
#endif /* USE_5005THREADS */

    if (ps)
        sv_setpv((SV*)cv, ps);

    if (PL_error_count) {
        op_free(block);
        block = Nullop;
        if (name) {
            char *s = strrchr(name, ':');
            s = s ? s+1 : name;
            if (strEQ(s, "BEGIN")) {
                char *not_safe =
                    "BEGIN not safe after errors--compilation aborted";
                if (PL_in_eval & EVAL_KEEPERR)
                    Perl_croak(aTHX_ not_safe);
                else {
                    /* force display of errors found but not reported */
                    sv_catpv(ERRSV, not_safe);
                    Perl_croak(aTHX_ "%"SVf, ERRSV);
                }
            }
        }
    }
    if (!block)
        goto done;

    if (CvLVALUE(cv)) {
        CvROOT(cv) = newUNOP(OP_LEAVESUBLV, 0,
                             mod(scalarseq(block), OP_LEAVESUBLV));
    }
    else {
        /* This makes sub {}; work as expected.  */
        if (block->op_type == OP_STUB) {
            op_free(block);
            block = newSTATEOP(0, Nullch, 0);
        }
        CvROOT(cv) = newUNOP(OP_LEAVESUB, 0, scalarseq(block));
    }
    CvROOT(cv)->op_private |= OPpREFCOUNTED;
    OpREFCNT_set(CvROOT(cv), 1);
    CvSTART(cv) = LINKLIST(CvROOT(cv));
    CvROOT(cv)->op_next = 0;
    CALL_PEEP(CvSTART(cv));

    /* now that optimizer has done its work, adjust pad values */

    pad_tidy(CvCLONE(cv) ? padtidy_SUBCLONE : padtidy_SUB);

    if (CvCLONE(cv)) {
        assert(!CvCONST(cv));
        if (ps && !*ps && op_const_sv(block, cv))
            CvCONST_on(cv);
    }

    if (name || aname) {
        char *s;
        char *tname = (name ? name : aname);

        if (PERLDB_SUBLINE && PL_curstash != PL_debstash) {
            SV *sv = NEWSV(0,0);
            SV *tmpstr = sv_newmortal();
            GV *db_postponed = gv_fetchpv("DB::postponed", GV_ADDMULTI, SVt_PVHV);
            CV *pcv;
            HV *hv;

            Perl_sv_setpvf(aTHX_ sv, "%s:%ld-%ld",
                           CopFILE(PL_curcop),
                           (long)PL_subline, (long)CopLINE(PL_curcop));
            gv_efullname3(tmpstr, gv, Nullch);
            hv_store(GvHV(PL_DBsub), SvPVX(tmpstr), SvCUR(tmpstr), sv, 0);
            hv = GvHVn(db_postponed);
            if (HvFILL(hv) > 0 && hv_exists(hv, SvPVX(tmpstr), SvCUR(tmpstr))
                && (pcv = GvCV(db_postponed)))
            {
                dSP;
                PUSHMARK(SP);
                XPUSHs(tmpstr);
                PUTBACK;
                call_sv((SV*)pcv, G_DISCARD);
            }
        }

        if ((s = strrchr(tname,':')))
            s++;
        else
            s = tname;

        if (*s != 'B' && *s != 'E' && *s != 'C' && *s != 'I')
            goto done;

        if (strEQ(s, "BEGIN")) {
            I32 oldscope = PL_scopestack_ix;
            ENTER;
            SAVECOPFILE(&PL_compiling);
            SAVECOPLINE(&PL_compiling);

            if (!PL_beginav)
                PL_beginav = newAV();
            DEBUG_x( dump_sub(gv) );
            av_push(PL_beginav, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
            call_list(oldscope, PL_beginav);

            PL_curcop = &PL_compiling;
            PL_compiling.op_private = (U8)(PL_hints & HINT_PRIVATE_MASK);
            LEAVE;
        }
        else if (strEQ(s, "END") && !PL_error_count) {
            if (!PL_endav)
                PL_endav = newAV();
            DEBUG_x( dump_sub(gv) );
            av_unshift(PL_endav, 1);
            av_store(PL_endav, 0, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
        else if (strEQ(s, "CHECK") && !PL_error_count) {
            if (!PL_checkav)
                PL_checkav = newAV();
            DEBUG_x( dump_sub(gv) );
            if (PL_main_start && ckWARN(WARN_VOID))
                Perl_warner(aTHX_ packWARN(WARN_VOID), "Too late to run CHECK block");
            av_unshift(PL_checkav, 1);
            av_store(PL_checkav, 0, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
        else if (strEQ(s, "INIT") && !PL_error_count) {
            if (!PL_initav)
                PL_initav = newAV();
            DEBUG_x( dump_sub(gv) );
            if (PL_main_start && ckWARN(WARN_VOID))
                Perl_warner(aTHX_ packWARN(WARN_VOID), "Too late to run INIT block");
            av_push(PL_initav, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
    }

  done:
    PL_copline = NOLINE;
    LEAVE_SCOPE(floor);
    return cv;
}

/* XXX unsafe for threads if eval_owner isn't held */
/*
=for apidoc newCONSTSUB

Creates a constant sub equivalent to Perl C<sub FOO () { 123 }> which is
eligible for inlining at compile-time.

=cut
*/

CV *
Perl_newCONSTSUB(pTHX_ HV *stash, char *name, SV *sv)
{
    CV* cv;

    ENTER;

    SAVECOPLINE(PL_curcop);
    CopLINE_set(PL_curcop, PL_copline);

    SAVEHINTS();
    PL_hints &= ~HINT_BLOCK_SCOPE;

    if (stash) {
        SAVESPTR(PL_curstash);
        SAVECOPSTASH(PL_curcop);
        PL_curstash = stash;
        CopSTASH_set(PL_curcop,stash);
    }

    cv = newXS(name, const_sv_xsub, savepv(CopFILE(PL_curcop)));
    CvXSUBANY(cv).any_ptr = sv;
    CvCONST_on(cv);
    sv_setpv((SV*)cv, "");  /* prototype is "" */

    if (stash)
        CopSTASH_free(PL_curcop);

    LEAVE;

    return cv;
}

/*
=for apidoc U||newXS

Used by C<xsubpp> to hook up XSUBs as Perl subs.

=cut
*/

CV *
Perl_newXS(pTHX_ char *name, XSUBADDR_t subaddr, char *filename)
{
    GV *gv = gv_fetchpv(name ? name :
                        (PL_curstash ? "__ANON__" : "__ANON__::__ANON__"),
                        GV_ADDMULTI, SVt_PVCV);
    register CV *cv;

    if ((cv = (name ? GvCV(gv) : Nullcv))) {
        if (GvCVGEN(gv)) {
            /* just a cached method */
            SvREFCNT_dec(cv);
            cv = 0;
        }
        else if (CvROOT(cv) || CvXSUB(cv) || GvASSUMECV(gv)) {
            /* already defined (or promised) */
            if (ckWARN(WARN_REDEFINE) && !(CvGV(cv) && GvSTASH(CvGV(cv))
                            && strEQ(HvNAME(GvSTASH(CvGV(cv))), "autouse"))) {
                line_t oldline = CopLINE(PL_curcop);
                if (PL_copline != NOLINE)
                    CopLINE_set(PL_curcop, PL_copline);
                Perl_warner(aTHX_ packWARN(WARN_REDEFINE),
                            CvCONST(cv) ? "Constant subroutine %s redefined"
                                        : "Subroutine %s redefined"
                            ,name);
                CopLINE_set(PL_curcop, oldline);
            }
            SvREFCNT_dec(cv);
            cv = 0;
        }
    }

    if (cv)                             /* must reuse cv if autoloaded */
        cv_undef(cv);
    else {
        cv = (CV*)NEWSV(1105,0);
        sv_upgrade((SV *)cv, SVt_PVCV);
        if (name) {
            GvCV(gv) = cv;
            GvCVGEN(gv) = 0;
            PL_sub_generation++;
        }
    }
    CvGV(cv) = gv;
#ifdef USE_5005THREADS
    New(666, CvMUTEXP(cv), 1, perl_mutex);
    MUTEX_INIT(CvMUTEXP(cv));
    CvOWNER(cv) = 0;
#endif /* USE_5005THREADS */
    (void)gv_fetchfile(filename);
    CvFILE(cv) = filename;      /* NOTE: not copied, as it is expected to be
                                   an external constant string */
    CvXSUB(cv) = subaddr;

    if (name) {
        char *s = strrchr(name,':');
        if (s)
            s++;
        else
            s = name;

        if (*s != 'B' && *s != 'E' && *s != 'C' && *s != 'I')
            goto done;

        if (strEQ(s, "BEGIN")) {
            if (!PL_beginav)
                PL_beginav = newAV();
            av_push(PL_beginav, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
        else if (strEQ(s, "END")) {
            if (!PL_endav)
                PL_endav = newAV();
            av_unshift(PL_endav, 1);
            av_store(PL_endav, 0, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
        else if (strEQ(s, "CHECK")) {
            if (!PL_checkav)
                PL_checkav = newAV();
            if (PL_main_start && ckWARN(WARN_VOID))
                Perl_warner(aTHX_ packWARN(WARN_VOID), "Too late to run CHECK block");
            av_unshift(PL_checkav, 1);
            av_store(PL_checkav, 0, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
        else if (strEQ(s, "INIT")) {
            if (!PL_initav)
                PL_initav = newAV();
            if (PL_main_start && ckWARN(WARN_VOID))
                Perl_warner(aTHX_ packWARN(WARN_VOID), "Too late to run INIT block");
            av_push(PL_initav, (SV*)cv);
            GvCV(gv) = 0;               /* cv has been hijacked */
        }
    }
    else
        CvANON_on(cv);

done:
    return cv;
}

void
Perl_newFORM(pTHX_ I32 floor, OP *o, OP *block)
{
    register CV *cv;
    char *name;
    GV *gv;
    STRLEN n_a;

    if (o)
        name = SvPVx(cSVOPo->op_sv, n_a);
    else
        name = "STDOUT";
    gv = gv_fetchpv(name,TRUE, SVt_PVFM);
#ifdef GV_UNIQUE_CHECK
    if (GvUNIQUE(gv)) {
        Perl_croak(aTHX_ "Bad symbol for form (GV is unique)");
    }
#endif
    GvMULTI_on(gv);
    if ((cv = GvFORM(gv))) {
        if (ckWARN(WARN_REDEFINE)) {
            line_t oldline = CopLINE(PL_curcop);
            if (PL_copline != NOLINE)
                CopLINE_set(PL_curcop, PL_copline);
            Perl_warner(aTHX_ packWARN(WARN_REDEFINE), "Format %s redefined",name);
            CopLINE_set(PL_curcop, oldline);
        }
        SvREFCNT_dec(cv);
    }
    cv = PL_compcv;
    GvFORM(gv) = cv;
    CvGV(cv) = gv;
    CvFILE_set_from_cop(cv, PL_curcop);


    pad_tidy(padtidy_FORMAT);
    CvROOT(cv) = newUNOP(OP_LEAVEWRITE, 0, scalarseq(block));
    CvROOT(cv)->op_private |= OPpREFCOUNTED;
    OpREFCNT_set(CvROOT(cv), 1);
    CvSTART(cv) = LINKLIST(CvROOT(cv));
    CvROOT(cv)->op_next = 0;
    CALL_PEEP(CvSTART(cv));
    op_free(o);
    PL_copline = NOLINE;
    LEAVE_SCOPE(floor);
}

OP *
Perl_newANONLIST(pTHX_ OP *o)
{
    return newUNOP(OP_REFGEN, 0,
        mod(list(convert(OP_ANONLIST, 0, o)), OP_REFGEN));
}

OP *
Perl_newANONHASH(pTHX_ OP *o)
{
    return newUNOP(OP_REFGEN, 0,
        mod(list(convert(OP_ANONHASH, 0, o)), OP_REFGEN));
}

OP *
Perl_newANONSUB(pTHX_ I32 floor, OP *proto, OP *block)
{
    return newANONATTRSUB(floor, proto, Nullop, block);
}

OP *
Perl_newANONATTRSUB(pTHX_ I32 floor, OP *proto, OP *attrs, OP *block)
{
    return newUNOP(OP_REFGEN, 0,
        newSVOP(OP_ANONCODE, 0,
                (SV*)newATTRSUB(floor, 0, proto, attrs, block)));
}

OP *
Perl_oopsAV(pTHX_ OP *o)
{
    switch (o->op_type) {
    case OP_PADSV:
        o->op_type = OP_PADAV;
        o->op_ppaddr = PL_ppaddr[OP_PADAV];
        return ref(o, OP_RV2AV);

    case OP_RV2SV:
        o->op_type = OP_RV2AV;
        o->op_ppaddr = PL_ppaddr[OP_RV2AV];
        ref(o, OP_RV2AV);
        break;

    default:
        if (ckWARN_d(WARN_INTERNAL))
            Perl_warner(aTHX_ packWARN(WARN_INTERNAL), "oops: oopsAV");
        break;
    }
    return o;
}

OP *
Perl_oopsHV(pTHX_ OP *o)
{
    switch (o->op_type) {
    case OP_PADSV:
    case OP_PADAV:
        o->op_type = OP_PADHV;
        o->op_ppaddr = PL_ppaddr[OP_PADHV];
        return ref(o, OP_RV2HV);

    case OP_RV2SV:
    case OP_RV2AV:
        o->op_type = OP_RV2HV;
        o->op_ppaddr = PL_ppaddr[OP_RV2HV];
        ref(o, OP_RV2HV);
        break;

    default:
        if (ckWARN_d(WARN_INTERNAL))
            Perl_warner(aTHX_ packWARN(WARN_INTERNAL), "oops: oopsHV");
        break;
    }
    return o;
}

OP *
Perl_newAVREF(pTHX_ OP *o)
{
    if (o->op_type == OP_PADANY) {
        o->op_type = OP_PADAV;
        o->op_ppaddr = PL_ppaddr[OP_PADAV];
        return o;
    }
    else if ((o->op_type == OP_RV2AV || o->op_type == OP_PADAV)
                && ckWARN(WARN_DEPRECATED)) {
        Perl_warner(aTHX_ packWARN(WARN_DEPRECATED),
                "Using an array as a reference is deprecated");
    }
    return newUNOP(OP_RV2AV, 0, scalar(o));
}

OP *
Perl_newGVREF(pTHX_ I32 type, OP *o)
{
    if (type == OP_MAPSTART || type == OP_GREPSTART || type == OP_SORT)
        return newUNOP(OP_NULL, 0, o);
    return ref(newUNOP(OP_RV2GV, OPf_REF, o), type);
}

OP *
Perl_newHVREF(pTHX_ OP *o)
{
    if (o->op_type == OP_PADANY) {
        o->op_type = OP_PADHV;
        o->op_ppaddr = PL_ppaddr[OP_PADHV];
        return o;
    }
    else if ((o->op_type == OP_RV2HV || o->op_type == OP_PADHV)
                && ckWARN(WARN_DEPRECATED)) {
        Perl_warner(aTHX_ packWARN(WARN_DEPRECATED),
                "Using a hash as a reference is deprecated");
    }
    return newUNOP(OP_RV2HV, 0, scalar(o));
}

OP *
Perl_oopsCV(pTHX_ OP *o)
{
    Perl_croak(aTHX_ "NOT IMPL LINE %d",__LINE__);
    /* STUB */
    return o;
}

OP *
Perl_newCVREF(pTHX_ I32 flags, OP *o)
{
    return newUNOP(OP_RV2CV, flags, scalar(o));
}

OP *
Perl_newSVREF(pTHX_ OP *o)
{
    if (o->op_type == OP_PADANY) {
        o->op_type = OP_PADSV;
        o->op_ppaddr = PL_ppaddr[OP_PADSV];
        return o;
    }
    else if (o->op_type == OP_THREADSV && !(o->op_flags & OPpDONE_SVREF)) {
        o->op_flags |= OPpDONE_SVREF;
        return o;
    }
    return newUNOP(OP_RV2SV, 0, scalar(o));
}

/* Check routines. See the comments at the top of this file for details
 * on when these are called */

OP *
Perl_ck_anoncode(pTHX_ OP *o)
{
    cSVOPo->op_targ = pad_add_anon(cSVOPo->op_sv, o->op_type);
    cSVOPo->op_sv = Nullsv;
    return o;
}

OP *
Perl_ck_bitop(pTHX_ OP *o)
{
#define OP_IS_NUMCOMPARE(op) \
        ((op) == OP_LT   || (op) == OP_I_LT || \
         (op) == OP_GT   || (op) == OP_I_GT || \
         (op) == OP_LE   || (op) == OP_I_LE || \
         (op) == OP_GE   || (op) == OP_I_GE || \
         (op) == OP_EQ   || (op) == OP_I_EQ || \
         (op) == OP_NE   || (op) == OP_I_NE || \
         (op) == OP_NCMP || (op) == OP_I_NCMP)
    o->op_private = (U8)(PL_hints & HINT_PRIVATE_MASK);
    if (!(o->op_flags & OPf_STACKED) /* Not an assignment */
            && (o->op_type == OP_BIT_OR
             || o->op_type == OP_BIT_AND
             || o->op_type == OP_BIT_XOR))
    {
        OP * left = cBINOPo->op_first;
        OP * right = left->op_sibling;
        if ((OP_IS_NUMCOMPARE(left->op_type) &&
                (left->op_flags & OPf_PARENS) == 0) ||
            (OP_IS_NUMCOMPARE(right->op_type) &&
                (right->op_flags & OPf_PARENS) == 0))
            if (ckWARN(WARN_PRECEDENCE))
                Perl_warner(aTHX_ packWARN(WARN_PRECEDENCE),
                        "Possible precedence problem on bitwise %c operator",
                        o->op_type == OP_BIT_OR ? '|'
                            : o->op_type == OP_BIT_AND ? '&' : '^'
                        );
    }
    return o;
}

OP *
Perl_ck_concat(pTHX_ OP *o)
{
    OP *kid = cUNOPo->op_first;
    if (kid->op_type == OP_CONCAT && !(kid->op_private & OPpTARGET_MY) &&
            !(kUNOP->op_first->op_flags & OPf_MOD))
        o->op_flags |= OPf_STACKED;
    return o;
}

OP *
Perl_ck_spair(pTHX_ OP *o)
{
    if (o->op_flags & OPf_KIDS) {
        OP* newop;
        OP* kid;
        OPCODE type = o->op_type;
        o = modkids(ck_fun(o), type);
        kid = cUNOPo->op_first;
        newop = kUNOP->op_first->op_sibling;
        if (newop &&
            (newop->op_sibling ||
             !(PL_opargs[newop->op_type] & OA_RETSCALAR) ||
             newop->op_type == OP_PADAV || newop->op_type == OP_PADHV ||
             newop->op_type == OP_RV2AV || newop->op_type == OP_RV2HV)) {

            return o;
        }
        op_free(kUNOP->op_first);
        kUNOP->op_first = newop;
    }
    o->op_ppaddr = PL_ppaddr[++o->op_type];
    return ck_fun(o);
}

OP *
Perl_ck_delete(pTHX_ OP *o)
{
    o = ck_fun(o);
    o->op_private = 0;
    if (o->op_flags & OPf_KIDS) {
        OP *kid = cUNOPo->op_first;
        switch (kid->op_type) {
        case OP_ASLICE:
            o->op_flags |= OPf_SPECIAL;
            /* FALL THROUGH */
        case OP_HSLICE:
            o->op_private |= OPpSLICE;
            break;
        case OP_AELEM:
            o->op_flags |= OPf_SPECIAL;
            /* FALL THROUGH */
        case OP_HELEM:
            break;
        default:
            Perl_croak(aTHX_ "%s argument is not a HASH or ARRAY element or slice",
                  OP_DESC(o));
        }
        op_null(kid);
    }
    return o;
}

OP *
Perl_ck_die(pTHX_ OP *o)
{
#ifdef VMS
    if (VMSISH_HUSHED) o->op_private |= OPpHUSH_VMSISH;
#endif
    return ck_fun(o);
}

OP *
Perl_ck_eof(pTHX_ OP *o)
{
    I32 type = o->op_type;

    if (o->op_flags & OPf_KIDS) {
        if (cLISTOPo->op_first->op_type == OP_STUB) {
            op_free(o);
            o = newUNOP(type, OPf_SPECIAL, newGVOP(OP_GV, 0, PL_argvgv));
        }
        return ck_fun(o);
    }
    return o;
}

OP *
Perl_ck_eval(pTHX_ OP *o)
{
    PL_hints |= HINT_BLOCK_SCOPE;
    if (o->op_flags & OPf_KIDS) {
        SVOP *kid = (SVOP*)cUNOPo->op_first;

        if (!kid) {
            o->op_flags &= ~OPf_KIDS;
            op_null(o);
        }
        else if (kid->op_type == OP_LINESEQ || kid->op_type == OP_STUB) {
            LOGOP *enter;

            cUNOPo->op_first = 0;
            op_free(o);

            NewOp(1101, enter, 1, LOGOP);
            enter->op_type = OP_ENTERTRY;
            enter->op_ppaddr = PL_ppaddr[OP_ENTERTRY];
            enter->op_private = 0;

            /* establish postfix order */
            enter->op_next = (OP*)enter;

            o = prepend_elem(OP_LINESEQ, (OP*)enter, (OP*)kid);
            o->op_type = OP_LEAVETRY;
            o->op_ppaddr = PL_ppaddr[OP_LEAVETRY];
            enter->op_other = o;
            return o;
        }
        else
            scalar((OP*)kid);
    }
    else {
        op_free(o);
        o = newUNOP(OP_ENTEREVAL, 0, newDEFSVOP());
    }
    o->op_targ = (PADOFFSET)PL_hints;
    return o;
}

OP *
Perl_ck_exit(pTHX_ OP *o)
{
#ifdef VMS
    HV *table = GvHV(PL_hintgv);
    if (table) {
       SV **svp = hv_fetch(table, "vmsish_exit", 11, FALSE);
       if (svp && *svp && SvTRUE(*svp))
           o->op_private |= OPpEXIT_VMSISH;
    }
    if (VMSISH_HUSHED) o->op_private |= OPpHUSH_VMSISH;
#endif
    return ck_fun(o);
}

OP *
Perl_ck_exec(pTHX_ OP *o)
{
    OP *kid;
    if (o->op_flags & OPf_STACKED) {
        o = ck_fun(o);
        kid = cUNOPo->op_first->op_sibling;
        if (kid->op_type == OP_RV2GV)
            op_null(kid);
    }
    else
        o = listkids(o);
    return o;
}

OP *
Perl_ck_exists(pTHX_ OP *o)
{
    o = ck_fun(o);
    if (o->op_flags & OPf_KIDS) {
        OP *kid = cUNOPo->op_first;
        if (kid->op_type == OP_ENTERSUB) {
            (void) ref(kid, o->op_type);
            if (kid->op_type != OP_RV2CV && !PL_error_count)
                Perl_croak(aTHX_ "%s argument is not a subroutine name",
                            OP_DESC(o));
            o->op_private |= OPpEXISTS_SUB;
        }
        else if (kid->op_type == OP_AELEM)
            o->op_flags |= OPf_SPECIAL;
        else if (kid->op_type != OP_HELEM)
            Perl_croak(aTHX_ "%s argument is not a HASH or ARRAY element",
                        OP_DESC(o));
        op_null(kid);
    }
    return o;
}

#if 0
OP *
Perl_ck_gvconst(pTHX_ register OP *o)
{
    o = fold_constants(o);
    if (o->op_type == OP_CONST)
        o->op_type = OP_GV;
    return o;
}
#endif

OP *
Perl_ck_rvconst(pTHX_ register OP *o)
{
    SVOP *kid = (SVOP*)cUNOPo->op_first;

    o->op_private |= (PL_hints & HINT_STRICT_REFS);
    if (kid->op_type == OP_CONST) {
        char *name;
        int iscv;
        GV *gv;
        SV *kidsv = kid->op_sv;
        STRLEN n_a;

        /* Is it a constant from cv_const_sv()? */
        if (SvROK(kidsv) && SvREADONLY(kidsv)) {
            SV *rsv = SvRV(kidsv);
            int svtype = SvTYPE(rsv);
            char *badtype = Nullch;

            switch (o->op_type) {
            case OP_RV2SV:
                if (svtype > SVt_PVMG)
                    badtype = "a SCALAR";
                break;
            case OP_RV2AV:
                if (svtype != SVt_PVAV)
                    badtype = "an ARRAY";
                break;
            case OP_RV2HV:
                if (svtype != SVt_PVHV) {
                    if (svtype == SVt_PVAV) {   /* pseudohash? */
                        SV **ksv = av_fetch((AV*)rsv, 0, FALSE);
                        if (ksv && SvROK(*ksv)
                            && SvTYPE(SvRV(*ksv)) == SVt_PVHV)
                        {
                                break;
                        }
                    }
                    badtype = "a HASH";
                }
                break;
            case OP_RV2CV:
                if (svtype != SVt_PVCV)
                    badtype = "a CODE";
                break;
            }
            if (badtype)
                Perl_croak(aTHX_ "Constant is not %s reference", badtype);
            return o;
        }
        name = SvPV(kidsv, n_a);
        if ((PL_hints & HINT_STRICT_REFS) && (kid->op_private & OPpCONST_BARE)) {
            char *badthing = Nullch;
            switch (o->op_type) {
            case OP_RV2SV:
                badthing = "a SCALAR";
                break;
            case OP_RV2AV:
                badthing = "an ARRAY";
                break;
            case OP_RV2HV:
                badthing = "a HASH";
                break;
            }
            if (badthing)
                Perl_croak(aTHX_
          "Can't use bareword (\"%s\") as %s ref while \"strict refs\" in use",
                      name, badthing);
        }
        /*
         * This is a little tricky.  We only want to add the symbol if we
         * didn't add it in the lexer.  Otherwise we get duplicate strict
         * warnings.  But if we didn't add it in the lexer, we must at
         * least pretend like we wanted to add it even if it existed before,
         * or we get possible typo warnings.  OPpCONST_ENTERED says
         * whether the lexer already added THIS instance of this symbol.
         */
        iscv = (o->op_type == OP_RV2CV) * 2;
        do {
            gv = gv_fetchpv(name,
                iscv | !(kid->op_private & OPpCONST_ENTERED),
                iscv
                    ? SVt_PVCV
                    : o->op_type == OP_RV2SV
                        ? SVt_PV
                        : o->op_type == OP_RV2AV
                            ? SVt_PVAV
                            : o->op_type == OP_RV2HV
                                ? SVt_PVHV
                                : SVt_PVGV);
        } while (!gv && !(kid->op_private & OPpCONST_ENTERED) && !iscv++);
        if (gv) {
            kid->op_type = OP_GV;
            SvREFCNT_dec(kid->op_sv);
#ifdef USE_ITHREADS
            /* XXX hack: dependence on sizeof(PADOP) <= sizeof(SVOP) */
            kPADOP->op_padix = pad_alloc(OP_GV, SVs_PADTMP);
            SvREFCNT_dec(PAD_SVl(kPADOP->op_padix));
            GvIN_PAD_on(gv);
            PAD_SETSV(kPADOP->op_padix, (SV*) SvREFCNT_inc(gv));
#else
            kid->op_sv = SvREFCNT_inc(gv);
#endif
            kid->op_private = 0;
            kid->op_ppaddr = PL_ppaddr[OP_GV];
        }
    }
    return o;
}

OP *
Perl_ck_ftst(pTHX_ OP *o)
{
    I32 type = o->op_type;

    if (o->op_flags & OPf_REF) {
        /* nothing */
    }
    else if (o->op_flags & OPf_KIDS && cUNOPo->op_first->op_type != OP_STUB) {
        SVOP *kid = (SVOP*)cUNOPo->op_first;

        if (kid->op_type == OP_CONST && (kid->op_private & OPpCONST_BARE)) {
            STRLEN n_a;
            OP *newop = newGVOP(type, OPf_REF,
                gv_fetchpv(SvPVx(kid->op_sv, n_a), TRUE, SVt_PVIO));
            op_free(o);
            o = newop;
        }
        else {
          if ((PL_hints & HINT_FILETEST_ACCESS) &&
              OP_IS_FILETEST_ACCESS(o))
            o->op_private |= OPpFT_ACCESS;
        }
    }
    else {
        op_free(o);
        if (type == OP_FTTTY)
            o = newGVOP(type, OPf_REF, PL_stdingv);
        else
            o = newUNOP(type, 0, newDEFSVOP());
    }
    return o;
}

OP *
Perl_ck_fun(pTHX_ OP *o)
{
    register OP *kid;
    OP **tokid;
    OP *sibl;
    I32 numargs = 0;
    int type = o->op_type;
    register I32 oa = PL_opargs[type] >> OASHIFT;

    if (o->op_flags & OPf_STACKED) {
        if ((oa & OA_OPTIONAL) && (oa >> 4) && !((oa >> 4) & OA_OPTIONAL))
            oa &= ~OA_OPTIONAL;
        else
            return no_fh_allowed(o);
    }

    if (o->op_flags & OPf_KIDS) {
        STRLEN n_a;
        tokid = &cLISTOPo->op_first;
        kid = cLISTOPo->op_first;
        if (kid->op_type == OP_PUSHMARK ||
            (kid->op_type == OP_NULL && kid->op_targ == OP_PUSHMARK))
        {
            tokid = &kid->op_sibling;
            kid = kid->op_sibling;
        }
        if (!kid && PL_opargs[type] & OA_DEFGV)
            *tokid = kid = newDEFSVOP();

        while (oa && kid) {
            numargs++;
            sibl = kid->op_sibling;
            switch (oa & 7) {
            case OA_SCALAR:
                /* list seen where single (scalar) arg expected? */
                if (numargs == 1 && !(oa >> 4)
                    && kid->op_type == OP_LIST && type != OP_SCALAR)
                {
                    return too_many_arguments(o,PL_op_desc[type]);
                }
                scalar(kid);
                break;
            case OA_LIST:
                if (oa < 16) {
                    kid = 0;
                    continue;
                }
                else
                    list(kid);
                break;
            case OA_AVREF:
                if ((type == OP_PUSH || type == OP_UNSHIFT)
                    && !kid->op_sibling && ckWARN(WARN_SYNTAX))
                    Perl_warner(aTHX_ packWARN(WARN_SYNTAX),
                        "Useless use of %s with no values",
                        PL_op_desc[type]);

                if (kid->op_type == OP_CONST &&
                    (kid->op_private & OPpCONST_BARE))
                {
                    char *name = SvPVx(((SVOP*)kid)->op_sv, n_a);
                    OP *newop = newAVREF(newGVOP(OP_GV, 0,
                        gv_fetchpv(name, TRUE, SVt_PVAV) ));
                    if (ckWARN2(WARN_DEPRECATED, WARN_SYNTAX))
                        Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                            "Array @%s missing the @ in argument %"IVdf" of %s()",
                            name, (IV)numargs, PL_op_desc[type]);
                    op_free(kid);
                    kid = newop;
                    kid->op_sibling = sibl;
                    *tokid = kid;
                }
                else if (kid->op_type != OP_RV2AV && kid->op_type != OP_PADAV)
                    bad_type(numargs, "array", PL_op_desc[type], kid);
                mod(kid, type);
                break;
            case OA_HVREF:
                if (kid->op_type == OP_CONST &&
                    (kid->op_private & OPpCONST_BARE))
                {
                    char *name = SvPVx(((SVOP*)kid)->op_sv, n_a);
                    OP *newop = newHVREF(newGVOP(OP_GV, 0,
                        gv_fetchpv(name, TRUE, SVt_PVHV) ));
                    if (ckWARN2(WARN_DEPRECATED, WARN_SYNTAX))
                        Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                            "Hash %%%s missing the %% in argument %"IVdf" of %s()",
                            name, (IV)numargs, PL_op_desc[type]);
                    op_free(kid);
                    kid = newop;
                    kid->op_sibling = sibl;
                    *tokid = kid;
                }
                else if (kid->op_type != OP_RV2HV && kid->op_type != OP_PADHV)
                    bad_type(numargs, "hash", PL_op_desc[type], kid);
                mod(kid, type);
                break;
            case OA_CVREF:
                {
                    OP *newop = newUNOP(OP_NULL, 0, kid);
                    kid->op_sibling = 0;
                    linklist(kid);
                    newop->op_next = newop;
                    kid = newop;
                    kid->op_sibling = sibl;
                    *tokid = kid;
                }
                break;
            case OA_FILEREF:
                if (kid->op_type != OP_GV && kid->op_type != OP_RV2GV) {
                    if (kid->op_type == OP_CONST &&
                        (kid->op_private & OPpCONST_BARE))
                    {
                        OP *newop = newGVOP(OP_GV, 0,
                            gv_fetchpv(SvPVx(((SVOP*)kid)->op_sv, n_a), TRUE,
                                        SVt_PVIO) );
                        if (!(o->op_private & 1) && /* if not unop */
                            kid == cLISTOPo->op_last)
                            cLISTOPo->op_last = newop;
                        op_free(kid);
                        kid = newop;
                    }
                    else if (kid->op_type == OP_READLINE) {
                        /* neophyte patrol: open(<FH>), close(<FH>) etc. */
                        bad_type(numargs, "HANDLE", OP_DESC(o), kid);
                    }
                    else {
                        I32 flags = OPf_SPECIAL;
                        I32 priv = 0;
                        PADOFFSET targ = 0;

                        /* is this op a FH constructor? */
                        if (is_handle_constructor(o,numargs)) {
                            char *name = Nullch;
                            STRLEN len = 0;

                            flags = 0;
                            /* Set a flag to tell rv2gv to vivify
                             * need to "prove" flag does not mean something
                             * else already - NI-S 1999/05/07
                             */
                            priv = OPpDEREF;
                            if (kid->op_type == OP_PADSV) {
                                /*XXX DAPM 2002.08.25 tmp assert test */
                                /*XXX*/ assert(av_fetch(PL_comppad_name, (kid->op_targ), FALSE));
                                /*XXX*/ assert(*av_fetch(PL_comppad_name, (kid->op_targ), FALSE));

                                name = PAD_COMPNAME_PV(kid->op_targ);
                                /* SvCUR of a pad namesv can't be trusted
                                 * (see PL_generation), so calc its length
                                 * manually */
                                if (name)
                                    len = strlen(name);

                            }
                            else if (kid->op_type == OP_RV2SV
                                     && kUNOP->op_first->op_type == OP_GV)
                            {
                                GV *gv = cGVOPx_gv(kUNOP->op_first);
                                name = GvNAME(gv);
                                len = GvNAMELEN(gv);
                            }
                            else if (kid->op_type == OP_AELEM
                                     || kid->op_type == OP_HELEM)
                            {
                                 OP *op;

                                 name = 0;
                                 if ((op = ((BINOP*)kid)->op_first)) {
                                      SV *tmpstr = Nullsv;
                                      char *a =
                                           kid->op_type == OP_AELEM ?
                                           "[]" : "{}";
                                      if (((op->op_type == OP_RV2AV) ||
                                           (op->op_type == OP_RV2HV)) &&
                                          (op = ((UNOP*)op)->op_first) &&
                                          (op->op_type == OP_GV)) {
                                           /* packagevar $a[] or $h{} */
                                           GV *gv = cGVOPx_gv(op);
                                           if (gv)
                                                tmpstr =
                                                     Perl_newSVpvf(aTHX_
                                                                   "%s%c...%c",
                                                                   GvNAME(gv),
                                                                   a[0], a[1]);
                                      }
                                      else if (op->op_type == OP_PADAV
                                               || op->op_type == OP_PADHV) {
                                           /* lexicalvar $a[] or $h{} */
                                           char *padname =
                                                PAD_COMPNAME_PV(op->op_targ);
                                           if (padname)
                                                tmpstr =
                                                     Perl_newSVpvf(aTHX_
                                                                   "%s%c...%c",
                                                                   padname + 1,
                                                                   a[0], a[1]);
                                           
                                      }
                                      if (tmpstr) {
                                           name = SvPV(tmpstr, len);
                                           sv_2mortal(tmpstr);
                                      }
                                 }
                                 if (!name) {
                                      name = "__ANONIO__";
                                      len = 10;
                                 }
                                 mod(kid, type);
                            }
                            if (name) {
                                SV *namesv;
                                targ = pad_alloc(OP_RV2GV, SVs_PADTMP);
                                namesv = PAD_SVl(targ);
                                (void)SvUPGRADE(namesv, SVt_PV);
                                if (*name != '$')
                                    sv_setpvn(namesv, "$", 1);
                                sv_catpvn(namesv, name, len);
                            }
                        }
                        kid->op_sibling = 0;
                        kid = newUNOP(OP_RV2GV, flags, scalar(kid));
                        kid->op_targ = targ;
                        kid->op_private |= priv;
                    }
                    kid->op_sibling = sibl;
                    *tokid = kid;
                }
                scalar(kid);
                break;
            case OA_SCALARREF:
                mod(scalar(kid), type);
                break;
            }
            oa >>= 4;
            tokid = &kid->op_sibling;
            kid = kid->op_sibling;
        }
        o->op_private |= numargs;
        if (kid)
            return too_many_arguments(o,OP_DESC(o));
        listkids(o);
    }
    else if (PL_opargs[type] & OA_DEFGV) {
        op_free(o);
        return newUNOP(type, 0, newDEFSVOP());
    }

    if (oa) {
        while (oa & OA_OPTIONAL)
            oa >>= 4;
        if (oa && oa != OA_LIST)
            return too_few_arguments(o,OP_DESC(o));
    }
    return o;
}

OP *
Perl_ck_glob(pTHX_ OP *o)
{
    GV *gv;

    o = ck_fun(o);
    if ((o->op_flags & OPf_KIDS) && !cLISTOPo->op_first->op_sibling)
        append_elem(OP_GLOB, o, newDEFSVOP());

    if (!((gv = gv_fetchpv("glob", FALSE, SVt_PVCV))
          && GvCVu(gv) && GvIMPORTED_CV(gv)))
    {
        gv = gv_fetchpv("CORE::GLOBAL::glob", FALSE, SVt_PVCV);
    }

#if !defined(PERL_EXTERNAL_GLOB)
    /* XXX this can be tightened up and made more failsafe. */
    if (!(gv && GvCVu(gv) && GvIMPORTED_CV(gv))) {
        GV *glob_gv;
        ENTER;
        Perl_load_module(aTHX_ PERL_LOADMOD_NOIMPORT,
                newSVpvn("File::Glob", 10), Nullsv, Nullsv, Nullsv);
        gv = gv_fetchpv("CORE::GLOBAL::glob", FALSE, SVt_PVCV);
        glob_gv = gv_fetchpv("File::Glob::csh_glob", FALSE, SVt_PVCV);
        GvCV(gv) = GvCV(glob_gv);
        SvREFCNT_inc((SV*)GvCV(gv));
        GvIMPORTED_CV_on(gv);
        LEAVE;
    }
#endif /* PERL_EXTERNAL_GLOB */

    if (gv && GvCVu(gv) && GvIMPORTED_CV(gv)) {
        append_elem(OP_GLOB, o,
                    newSVOP(OP_CONST, 0, newSViv(PL_glob_index++)));
        o->op_type = OP_LIST;
        o->op_ppaddr = PL_ppaddr[OP_LIST];
        cLISTOPo->op_first->op_type = OP_PUSHMARK;
        cLISTOPo->op_first->op_ppaddr = PL_ppaddr[OP_PUSHMARK];
        cLISTOPo->op_first->op_targ = 0;
        o = newUNOP(OP_ENTERSUB, OPf_STACKED,
                    append_elem(OP_LIST, o,
                                scalar(newUNOP(OP_RV2CV, 0,
                                               newGVOP(OP_GV, 0, gv)))));
        o = newUNOP(OP_NULL, 0, ck_subr(o));
        o->op_targ = OP_GLOB;           /* hint at what it used to be */
        return o;
    }
    gv = newGVgen("main");
    gv_IOadd(gv);
    append_elem(OP_GLOB, o, newGVOP(OP_GV, 0, gv));
    scalarkids(o);
    return o;
}

OP *
Perl_ck_grep(pTHX_ OP *o)
{
    LOGOP *gwop;
    OP *kid;
    OPCODE type = o->op_type == OP_GREPSTART ? OP_GREPWHILE : OP_MAPWHILE;

    o->op_ppaddr = PL_ppaddr[OP_GREPSTART];
    NewOp(1101, gwop, 1, LOGOP);

    if (o->op_flags & OPf_STACKED) {
        OP* k;
        o = ck_sort(o);
        kid = cLISTOPo->op_first->op_sibling;
        if (!cUNOPx(kid)->op_next)
            Perl_croak(aTHX_ "panic: ck_grep");
        for (k = cUNOPx(kid)->op_first; k; k = k->op_next) {
            kid = k;
        }
        kid->op_next = (OP*)gwop;
        o->op_flags &= ~OPf_STACKED;
    }
    kid = cLISTOPo->op_first->op_sibling;
    if (type == OP_MAPWHILE)
        list(kid);
    else
        scalar(kid);
    o = ck_fun(o);
    if (PL_error_count)
        return o;
    kid = cLISTOPo->op_first->op_sibling;
    if (kid->op_type != OP_NULL)
        Perl_croak(aTHX_ "panic: ck_grep");
    kid = kUNOP->op_first;

    gwop->op_type = type;
    gwop->op_ppaddr = PL_ppaddr[type];
    gwop->op_first = listkids(o);
    gwop->op_flags |= OPf_KIDS;
    gwop->op_private = 1;
    gwop->op_other = LINKLIST(kid);
    gwop->op_targ = pad_alloc(type, SVs_PADTMP);
    kid->op_next = (OP*)gwop;

    kid = cLISTOPo->op_first->op_sibling;
    if (!kid || !kid->op_sibling)
        return too_few_arguments(o,OP_DESC(o));
    for (kid = kid->op_sibling; kid; kid = kid->op_sibling)
        mod(kid, OP_GREPSTART);

    return (OP*)gwop;
}

OP *
Perl_ck_index(pTHX_ OP *o)
{
    if (o->op_flags & OPf_KIDS) {
        OP *kid = cLISTOPo->op_first->op_sibling;       /* get past pushmark */
        if (kid)
            kid = kid->op_sibling;                      /* get past "big" */
        if (kid && kid->op_type == OP_CONST)
            fbm_compile(((SVOP*)kid)->op_sv, 0);
    }
    return ck_fun(o);
}

OP *
Perl_ck_lengthconst(pTHX_ OP *o)
{
    /* XXX length optimization goes here */
    return ck_fun(o);
}

OP *
Perl_ck_lfun(pTHX_ OP *o)
{
    OPCODE type = o->op_type;
    return modkids(ck_fun(o), type);
}

OP *
Perl_ck_defined(pTHX_ OP *o)            /* 19990527 MJD */
{
    if ((o->op_flags & OPf_KIDS) && ckWARN2(WARN_DEPRECATED, WARN_SYNTAX)) {
        switch (cUNOPo->op_first->op_type) {
        case OP_RV2AV:
            /* This is needed for
               if (defined %stash::)
               to work.   Do not break Tk.
               */
            break;                      /* Globals via GV can be undef */
        case OP_PADAV:
        case OP_AASSIGN:                /* Is this a good idea? */
            Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                        "defined(@array) is deprecated");
            Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                        "\t(Maybe you should just omit the defined()?)\n");
        break;
        case OP_RV2HV:
            /* This is needed for
               if (defined %stash::)
               to work.   Do not break Tk.
               */
            break;                      /* Globals via GV can be undef */
        case OP_PADHV:
            Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                        "defined(%%hash) is deprecated");
            Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
                        "\t(Maybe you should just omit the defined()?)\n");
            break;
        default:
            /* no warning */
            break;
        }
    }
    return ck_rfun(o);
}

OP *
Perl_ck_rfun(pTHX_ OP *o)
{
    OPCODE type = o->op_type;
    return refkids(ck_fun(o), type);
}

OP *
Perl_ck_listiob(pTHX_ OP *o)
{
    register OP *kid;

    kid = cLISTOPo->op_first;
    if (!kid) {
        o = force_list(o);
        kid = cLISTOPo->op_first;
    }
    if (kid->op_type == OP_PUSHMARK)
        kid = kid->op_sibling;
    if (kid && o->op_flags & OPf_STACKED)
        kid = kid->op_sibling;
    else if (kid && !kid->op_sibling) {         /* print HANDLE; */
        if (kid->op_type == OP_CONST && kid->op_private & OPpCONST_BARE) {
            o->op_flags |= OPf_STACKED; /* make it a filehandle */
            kid = newUNOP(OP_RV2GV, OPf_REF, scalar(kid));
            cLISTOPo->op_first->op_sibling = kid;
            cLISTOPo->op_last = kid;
            kid = kid->op_sibling;
        }
    }

    if (!kid)
        append_elem(o->op_type, o, newDEFSVOP());

    return listkids(o);
}

OP *
Perl_ck_sassign(pTHX_ OP *o)
{
    OP *kid = cLISTOPo->op_first;
    /* has a disposable target? */
    if ((PL_opargs[kid->op_type] & OA_TARGLEX)
        && !(kid->op_flags & OPf_STACKED)
        /* Cannot steal the second time! */
        && !(kid->op_private & OPpTARGET_MY))
    {
        OP *kkid = kid->op_sibling;

        /* Can just relocate the target. */
        if (kkid && kkid->op_type == OP_PADSV
            && !(kkid->op_private & OPpLVAL_INTRO))
        {
            kid->op_targ = kkid->op_targ;
            kkid->op_targ = 0;
            /* Now we do not need PADSV and SASSIGN. */
            kid->op_sibling = o->op_sibling;    /* NULL */
            cLISTOPo->op_first = NULL;
            op_free(o);
            op_free(kkid);
            kid->op_private |= OPpTARGET_MY;    /* Used for context settings */
            return kid;
        }
    }
    /* optimise C<my $x = undef> to C<my $x> */
    if (kid->op_type == OP_UNDEF) {
        OP *kkid = kid->op_sibling;
        if (kkid && kkid->op_type == OP_PADSV
                && (kkid->op_private & OPpLVAL_INTRO))
        {
            cLISTOPo->op_first = NULL;
            kid->op_sibling = NULL;
            op_free(o);
            op_free(kid);
            return kkid;
        }
    }
    return o;
}

OP *
Perl_ck_match(pTHX_ OP *o)
{
    o->op_private |= OPpRUNTIME;
    return o;
}

OP *
Perl_ck_method(pTHX_ OP *o)
{
    OP *kid = cUNOPo->op_first;
    if (kid->op_type == OP_CONST) {
        SV* sv = kSVOP->op_sv;
        if (!(strchr(SvPVX(sv), ':') || strchr(SvPVX(sv), '\''))) {
            OP *cmop;
            if (!SvREADONLY(sv) || !SvFAKE(sv)) {
                sv = newSVpvn_share(SvPVX(sv), SvCUR(sv), 0);
            }
            else {
                kSVOP->op_sv = Nullsv;
            }
            cmop = newSVOP(OP_METHOD_NAMED, 0, sv);
            op_free(o);
            return cmop;
        }
    }
    return o;
}

OP *
Perl_ck_null(pTHX_ OP *o)
{
    return o;
}

OP *
Perl_ck_open(pTHX_ OP *o)
{
    HV *table = GvHV(PL_hintgv);
    if (table) {
        SV **svp;
        I32 mode;
        svp = hv_fetch(table, "open_IN", 7, FALSE);
        if (svp && *svp) {
            mode = mode_from_discipline(*svp);
            if (mode & O_BINARY)
                o->op_private |= OPpOPEN_IN_RAW;
            else if (mode & O_TEXT)
                o->op_private |= OPpOPEN_IN_CRLF;
        }

        svp = hv_fetch(table, "open_OUT", 8, FALSE);
        if (svp && *svp) {
            mode = mode_from_discipline(*svp);
            if (mode & O_BINARY)
                o->op_private |= OPpOPEN_OUT_RAW;
            else if (mode & O_TEXT)
                o->op_private |= OPpOPEN_OUT_CRLF;
        }
    }
    if (o->op_type == OP_BACKTICK)
        return o;
    {
         /* In case of three-arg dup open remove strictness
          * from the last arg if it is a bareword. */
         OP *first = cLISTOPx(o)->op_first; /* The pushmark. */
         OP *last  = cLISTOPx(o)->op_last;  /* The bareword. */
         OP *oa;
         char *mode;

         if ((last->op_type == OP_CONST) &&             /* The bareword. */
             (last->op_private & OPpCONST_BARE) &&
             (last->op_private & OPpCONST_STRICT) &&
             (oa = first->op_sibling) &&                /* The fh. */
             (oa = oa->op_sibling) &&                   /* The mode. */
             SvPOK(((SVOP*)oa)->op_sv) &&
             (mode = SvPVX(((SVOP*)oa)->op_sv)) &&
             mode[0] == '>' && mode[1] == '&' &&        /* A dup open. */
             (last == oa->op_sibling))                  /* The bareword. */
              last->op_private &= ~OPpCONST_STRICT;
    }
    return ck_fun(o);
}

OP *
Perl_ck_repeat(pTHX_ OP *o)
{
    if (cBINOPo->op_first->op_flags & OPf_PARENS) {
        o->op_private |= OPpREPEAT_DOLIST;
        cBINOPo->op_first = force_list(cBINOPo->op_first);
    }
    else
        scalar(o);
    return o;
}

OP *
Perl_ck_require(pTHX_ OP *o)
{
    GV* gv;

    if (o->op_flags & OPf_KIDS) {       /* Shall we supply missing .pm? */
        SVOP *kid = (SVOP*)cUNOPo->op_first;

        if (kid->op_type == OP_CONST && (kid->op_private & OPpCONST_BARE)) {
            char *s;
            for (s = SvPVX(kid->op_sv); *s; s++) {
                if (*s == ':' && s[1] == ':') {
                    *s = '/';
                    Move(s+2, s+1, strlen(s+2)+1, char);
                    --SvCUR(kid->op_sv);
                }
            }
            if (SvREADONLY(kid->op_sv)) {
                SvREADONLY_off(kid->op_sv);
                sv_catpvn(kid->op_sv, ".pm", 3);
                SvREADONLY_on(kid->op_sv);
            }
            else
                sv_catpvn(kid->op_sv, ".pm", 3);
        }
    }

    /* handle override, if any */
    gv = gv_fetchpv("require", FALSE, SVt_PVCV);
    if (!(gv && GvCVu(gv) && GvIMPORTED_CV(gv)))
        gv = gv_fetchpv("CORE::GLOBAL::require", FALSE, SVt_PVCV);

    if (gv && GvCVu(gv) && GvIMPORTED_CV(gv)) {
        OP *kid = cUNOPo->op_first;
        cUNOPo->op_first = 0;
        op_free(o);
        return ck_subr(newUNOP(OP_ENTERSUB, OPf_STACKED,
                               append_elem(OP_LIST, kid,
                                           scalar(newUNOP(OP_RV2CV, 0,
                                                          newGVOP(OP_GV, 0,
                                                                  gv))))));
    }

    return ck_fun(o);
}

OP *
Perl_ck_return(pTHX_ OP *o)
{
    OP *kid;
    if (CvLVALUE(PL_compcv)) {
        for (kid = cLISTOPo->op_first->op_sibling; kid; kid = kid->op_sibling)
            mod(kid, OP_LEAVESUBLV);
    }
    return o;
}

#if 0
OP *
Perl_ck_retarget(pTHX_ OP *o)
{
    Perl_croak(aTHX_ "NOT IMPL LINE %d",__LINE__);
    /* STUB */
    return o;
}
#endif

OP *
Perl_ck_select(pTHX_ OP *o)
{
    OP* kid;
    if (o->op_flags & OPf_KIDS) {
        kid = cLISTOPo->op_first->op_sibling;   /* get past pushmark */
        if (kid && kid->op_sibling) {
            o->op_type = OP_SSELECT;
            o->op_ppaddr = PL_ppaddr[OP_SSELECT];
            o = ck_fun(o);
            return fold_constants(o);
        }
    }
    o = ck_fun(o);
    kid = cLISTOPo->op_first->op_sibling;    /* get past pushmark */
    if (kid && kid->op_type == OP_RV2GV)
        kid->op_private &= ~HINT_STRICT_REFS;
    return o;
}

OP *
Perl_ck_shift(pTHX_ OP *o)
{
    I32 type = o->op_type;

    if (!(o->op_flags & OPf_KIDS)) {
        OP *argop;

        op_free(o);
#ifdef USE_5005THREADS
        if (!CvUNIQUE(PL_compcv)) {
            argop = newOP(OP_PADAV, OPf_REF);
            argop->op_targ = 0;         /* PAD_SV(0) is @_ */
        }
        else {
            argop = newUNOP(OP_RV2AV, 0,
                scalar(newGVOP(OP_GV, 0,
                    gv_fetchpv("ARGV", TRUE, SVt_PVAV))));
        }
#else
        argop = newUNOP(OP_RV2AV, 0,
            scalar(newGVOP(OP_GV, 0, CvUNIQUE(PL_compcv) ? PL_argvgv : PL_defgv)));
#endif /* USE_5005THREADS */
        return newUNOP(type, 0, scalar(argop));
    }
    return scalar(modkids(ck_fun(o), type));
}

OP *
Perl_ck_sort(pTHX_ OP *o)
{
    OP *firstkid;

    if (o->op_type == OP_SORT && o->op_flags & OPf_STACKED)
        simplify_sort(o);
    firstkid = cLISTOPo->op_first->op_sibling;          /* get past pushmark */
    if (o->op_flags & OPf_STACKED) {                    /* may have been cleared */
        OP *k = NULL;
        OP *kid = cUNOPx(firstkid)->op_first;           /* get past null */

        if (kid->op_type == OP_SCOPE || kid->op_type == OP_LEAVE) {
            linklist(kid);
            if (kid->op_type == OP_SCOPE) {
                k = kid->op_next;
                kid->op_next = 0;
            }
            else if (kid->op_type == OP_LEAVE) {
                if (o->op_type == OP_SORT) {
                    op_null(kid);                       /* wipe out leave */
                    kid->op_next = kid;

                    for (k = kLISTOP->op_first->op_next; k; k = k->op_next) {
                        if (k->op_next == kid)
                            k->op_next = 0;
                        /* don't descend into loops */
                        else if (k->op_type == OP_ENTERLOOP
                                 || k->op_type == OP_ENTERITER)
                        {
                            k = cLOOPx(k)->op_lastop;
                        }
                    }
                }
                else
                    kid->op_next = 0;           /* just disconnect the leave */
                k = kLISTOP->op_first;
            }
            CALL_PEEP(k);

            kid = firstkid;
            if (o->op_type == OP_SORT) {
                /* provide scalar context for comparison function/block */
                kid = scalar(kid);
                kid->op_next = kid;
            }
            else
                kid->op_next = k;
            o->op_flags |= OPf_SPECIAL;
        }
        else if (kid->op_type == OP_RV2SV || kid->op_type == OP_PADSV)
            op_null(firstkid);

        firstkid = firstkid->op_sibling;
    }

    /* provide list context for arguments */
    if (o->op_type == OP_SORT)
        list(firstkid);

    return o;
}

STATIC void
S_simplify_sort(pTHX_ OP *o)
{
    register OP *kid = cLISTOPo->op_first->op_sibling;  /* get past pushmark */
    OP *k;
    int descending;
    GV *gv;
    const char *gvname;
    if (!(o->op_flags & OPf_STACKED))
        return;
    GvMULTI_on(gv_fetchpv("a", TRUE, SVt_PV));
    GvMULTI_on(gv_fetchpv("b", TRUE, SVt_PV));
    kid = kUNOP->op_first;                              /* get past null */
    if (kid->op_type != OP_SCOPE)
        return;
    kid = kLISTOP->op_last;                             /* get past scope */
    switch(kid->op_type) {
        case OP_NCMP:
        case OP_I_NCMP:
        case OP_SCMP:
            break;
        default:
            return;
    }
    k = kid;                                            /* remember this node*/
    if (kBINOP->op_first->op_type != OP_RV2SV)
        return;
    kid = kBINOP->op_first;                             /* get past cmp */
    if (kUNOP->op_first->op_type != OP_GV)
        return;
    kid = kUNOP->op_first;                              /* get past rv2sv */
    gv = kGVOP_gv;
    if (GvSTASH(gv) != PL_curstash)
        return;
    gvname = GvNAME(gv);
    if (*gvname == 'a' && gvname[1] == '\0')
        descending = 0;
    else if (*gvname == 'b' && gvname[1] == '\0')
        descending = 1;
    else
        return;

    kid = k;                                            /* back to cmp */
    if (kBINOP->op_last->op_type != OP_RV2SV)
        return;
    kid = kBINOP->op_last;                              /* down to 2nd arg */
    if (kUNOP->op_first->op_type != OP_GV)
        return;
    kid = kUNOP->op_first;                              /* get past rv2sv */
    gv = kGVOP_gv;
    if (GvSTASH(gv) != PL_curstash)
        return;
    gvname = GvNAME(gv);
    if ( descending
         ? !(*gvname == 'a' && gvname[1] == '\0')
         : !(*gvname == 'b' && gvname[1] == '\0'))
        return;
    o->op_flags &= ~(OPf_STACKED | OPf_SPECIAL);
    if (descending)
        o->op_private |= OPpSORT_DESCEND;
    if (k->op_type == OP_NCMP)
        o->op_private |= OPpSORT_NUMERIC;
    if (k->op_type == OP_I_NCMP)
        o->op_private |= OPpSORT_NUMERIC | OPpSORT_INTEGER;
    kid = cLISTOPo->op_first->op_sibling;
    cLISTOPo->op_first->op_sibling = kid->op_sibling; /* bypass old block */
    op_free(kid);                                     /* then delete it */
}

OP *
Perl_ck_split(pTHX_ OP *o)
{
    register OP *kid;

    if (o->op_flags & OPf_STACKED)
        return no_fh_allowed(o);

    kid = cLISTOPo->op_first;
    if (kid->op_type != OP_NULL)
        Perl_croak(aTHX_ "panic: ck_split");
    kid = kid->op_sibling;
    op_free(cLISTOPo->op_first);
    cLISTOPo->op_first = kid;
    if (!kid) {
        cLISTOPo->op_first = kid = newSVOP(OP_CONST, 0, newSVpvn(" ", 1));
        cLISTOPo->op_last = kid; /* There was only one element previously */
    }

    if (kid->op_type != OP_MATCH || kid->op_flags & OPf_STACKED) {
        OP *sibl = kid->op_sibling;
        kid->op_sibling = 0;
        kid = pmruntime( newPMOP(OP_MATCH, OPf_SPECIAL), kid, Nullop);
        if (cLISTOPo->op_first == cLISTOPo->op_last)
            cLISTOPo->op_last = kid;
        cLISTOPo->op_first = kid;
        kid->op_sibling = sibl;
    }

    kid->op_type = OP_PUSHRE;
    kid->op_ppaddr = PL_ppaddr[OP_PUSHRE];
    scalar(kid);
    if (ckWARN(WARN_REGEXP) && ((PMOP *)kid)->op_pmflags & PMf_GLOBAL) {
      Perl_warner(aTHX_ packWARN(WARN_REGEXP),
                  "Use of /g modifier is meaningless in split");
    }

    if (!kid->op_sibling)
        append_elem(OP_SPLIT, o, newDEFSVOP());

    kid = kid->op_sibling;
    scalar(kid);

    if (!kid->op_sibling)
        append_elem(OP_SPLIT, o, newSVOP(OP_CONST, 0, newSViv(0)));

    kid = kid->op_sibling;
    scalar(kid);

    if (kid->op_sibling)
        return too_many_arguments(o,OP_DESC(o));

    return o;
}

OP *
Perl_ck_join(pTHX_ OP *o)
{
    if (ckWARN(WARN_SYNTAX)) {
        OP *kid = cLISTOPo->op_first->op_sibling;
        if (kid && kid->op_type == OP_MATCH) {
            char *pmstr = "STRING";
            if (PM_GETRE(kPMOP))
                pmstr = PM_GETRE(kPMOP)->precomp;
            Perl_warner(aTHX_ packWARN(WARN_SYNTAX),
                        "/%s/ should probably be written as \"%s\"",
                        pmstr, pmstr);
        }
    }
    return ck_fun(o);
}

OP *
Perl_ck_subr(pTHX_ OP *o)
{
    OP *prev = ((cUNOPo->op_first->op_sibling)
             ? cUNOPo : ((UNOP*)cUNOPo->op_first))->op_first;
    OP *o2 = prev->op_sibling;
    OP *cvop;
    char *proto = 0;
    CV *cv = 0;
    GV *namegv = 0;
    int optional = 0;
    I32 arg = 0;
    I32 contextclass = 0;
    char *e = 0;
    STRLEN n_a;

    o->op_private |= OPpENTERSUB_HASTARG;
    for (cvop = o2; cvop->op_sibling; cvop = cvop->op_sibling) ;
    if (cvop->op_type == OP_RV2CV) {
        SVOP* tmpop;
        o->op_private |= (cvop->op_private & OPpENTERSUB_AMPER);
        op_null(cvop);          /* disable rv2cv */
        tmpop = (SVOP*)((UNOP*)cvop)->op_first;
        if (tmpop->op_type == OP_GV && !(o->op_private & OPpENTERSUB_AMPER)) {
            GV *gv = cGVOPx_gv(tmpop);
            cv = GvCVu(gv);
            if (!cv)
                tmpop->op_private |= OPpEARLY_CV;
            else if (SvPOK(cv)) {
                namegv = CvANON(cv) ? gv : CvGV(cv);
                proto = SvPV((SV*)cv, n_a);
            }
        }
    }
    else if (cvop->op_type == OP_METHOD || cvop->op_type == OP_METHOD_NAMED) {
        if (o2->op_type == OP_CONST)
            o2->op_private &= ~OPpCONST_STRICT;
        else if (o2->op_type == OP_LIST) {
            OP *o = ((UNOP*)o2)->op_first->op_sibling;
            if (o && o->op_type == OP_CONST)
                o->op_private &= ~OPpCONST_STRICT;
        }
    }
    o->op_private |= (PL_hints & HINT_STRICT_REFS);
    if (PERLDB_SUB && PL_curstash != PL_debstash)
        o->op_private |= OPpENTERSUB_DB;
    while (o2 != cvop) {
        if (proto) {
            switch (*proto) {
            case '\0':
                return too_many_arguments(o, gv_ename(namegv));
            case ';':
                optional = 1;
                proto++;
                continue;
            case '$':
                proto++;
                arg++;
                scalar(o2);
                break;
            case '%':
            case '@':
                list(o2);
                arg++;
                break;
            case '&':
                proto++;
                arg++;
                if (o2->op_type != OP_REFGEN && o2->op_type != OP_UNDEF)
                    bad_type(arg,
                        arg == 1 ? "block or sub {}" : "sub {}",
                        gv_ename(namegv), o2);
                break;
            case '*':
                /* '*' allows any scalar type, including bareword */
                proto++;
                arg++;
                if (o2->op_type == OP_RV2GV)
                    goto wrapref;       /* autoconvert GLOB -> GLOBref */
                else if (o2->op_type == OP_CONST)
                    o2->op_private &= ~OPpCONST_STRICT;
                else if (o2->op_type == OP_ENTERSUB) {
                    /* accidental subroutine, revert to bareword */
                    OP *gvop = ((UNOP*)o2)->op_first;
                    if (gvop && gvop->op_type == OP_NULL) {
                        gvop = ((UNOP*)gvop)->op_first;
                        if (gvop) {
                            for (; gvop->op_sibling; gvop = gvop->op_sibling)
                                ;
                            if (gvop &&
                                (gvop->op_private & OPpENTERSUB_NOPAREN) &&
                                (gvop = ((UNOP*)gvop)->op_first) &&
                                gvop->op_type == OP_GV)
                            {
                                GV *gv = cGVOPx_gv(gvop);
                                OP *sibling = o2->op_sibling;
                                SV *n = newSVpvn("",0);
                                op_free(o2);
                                gv_fullname4(n, gv, "", FALSE);
                                o2 = newSVOP(OP_CONST, 0, n);
                                prev->op_sibling = o2;
                                o2->op_sibling = sibling;
                            }
                        }
                    }
                }
                scalar(o2);
                break;
            case '[': case ']':
                 goto oops;
                 break;
            case '\\':
                proto++;
                arg++;
            again:
                switch (*proto++) {
                case '[':
                     if (contextclass++ == 0) {
                          e = strchr(proto, ']');
                          if (!e || e == proto)
                               goto oops;
                     }
                     else
                          goto oops;
                     goto again;
                     break;
                case ']':
                     if (contextclass) {
                         char *p = proto;
                         char s = *p;
                         contextclass = 0;
                         *p = '\0';
                         while (*--p != '[');
                         bad_type(arg, Perl_form(aTHX_ "one of %s", p),
                                 gv_ename(namegv), o2);
                         *proto = s;
                     } else
                          goto oops;
                     break;
                case '*':
                     if (o2->op_type == OP_RV2GV)
                          goto wrapref;
                     if (!contextclass)
                          bad_type(arg, "symbol", gv_ename(namegv), o2);
                     break;
                case '&':
                     if (o2->op_type == OP_ENTERSUB)
                          goto wrapref;
                     if (!contextclass)
                          bad_type(arg, "subroutine entry", gv_ename(namegv), o2);
                     break;
                case '$':
                    if (o2->op_type == OP_RV2SV ||
                        o2->op_type == OP_PADSV ||
                        o2->op_type == OP_HELEM ||
                        o2->op_type == OP_AELEM ||
                        o2->op_type == OP_THREADSV)
                         goto wrapref;
                    if (!contextclass)
                        bad_type(arg, "scalar", gv_ename(namegv), o2);
                     break;
                case '@':
                    if (o2->op_type == OP_RV2AV ||
                        o2->op_type == OP_PADAV)
                         goto wrapref;
                    if (!contextclass)
                        bad_type(arg, "array", gv_ename(namegv), o2);
                    break;
                case '%':
                    if (o2->op_type == OP_RV2HV ||
                        o2->op_type == OP_PADHV)
                         goto wrapref;
                    if (!contextclass)
                         bad_type(arg, "hash", gv_ename(namegv), o2);
                    break;
                wrapref:
                    {
                        OP* kid = o2;
                        OP* sib = kid->op_sibling;
                        kid->op_sibling = 0;
                        o2 = newUNOP(OP_REFGEN, 0, kid);
                        o2->op_sibling = sib;
                        prev->op_sibling = o2;
                    }
                    if (contextclass && e) {
                         proto = e + 1;
                         contextclass = 0;
                    }
                    break;
                default: goto oops;
                }
                if (contextclass)
                     goto again;
                break;
            case ' ':
                proto++;
                continue;
            default:
              oops:
                Perl_croak(aTHX_ "Malformed prototype for %s: %"SVf,
                           gv_ename(namegv), cv);
            }
        }
        else
            list(o2);
        mod(o2, OP_ENTERSUB);
        prev = o2;
        o2 = o2->op_sibling;
    }
    if (proto && !optional &&
          (*proto && *proto != '@' && *proto != '%' && *proto != ';'))
        return too_few_arguments(o, gv_ename(namegv));
    return o;
}

OP *
Perl_ck_svconst(pTHX_ OP *o)
{
    SvREADONLY_on(cSVOPo->op_sv);
    return o;
}

OP *
Perl_ck_trunc(pTHX_ OP *o)
{
    if (o->op_flags & OPf_KIDS) {
        SVOP *kid = (SVOP*)cUNOPo->op_first;

        if (kid->op_type == OP_NULL)
            kid = (SVOP*)kid->op_sibling;
        if (kid && kid->op_type == OP_CONST &&
            (kid->op_private & OPpCONST_BARE))
        {
            o->op_flags |= OPf_SPECIAL;
            kid->op_private &= ~OPpCONST_STRICT;
        }
    }
    return ck_fun(o);
}

OP *
Perl_ck_substr(pTHX_ OP *o)
{
    o = ck_fun(o);
    if ((o->op_flags & OPf_KIDS) && o->op_private == 4) {
        OP *kid = cLISTOPo->op_first;

        if (kid->op_type == OP_NULL)
            kid = kid->op_sibling;
        if (kid)
            kid->op_flags |= OPf_MOD;

    }
    return o;
}

/* A peephole optimizer.  We visit the ops in the order they're to execute.
 * See the comments at the top of this file for more details about when
 * peep() is called */

void
Perl_peep(pTHX_ register OP *o)
{
    register OP* oldop = 0;
    STRLEN n_a;

    if (!o || o->op_seq)
        return;
    ENTER;
    SAVEOP();
    SAVEVPTR(PL_curcop);
    for (; o; o = o->op_next) {
        if (o->op_seq)
            break;
        /* The special value -1 is used by the B::C compiler backend to indicate
         * that an op is statically defined and should not be freed */
        if (!PL_op_seqmax || PL_op_seqmax == (U16)-1)
            PL_op_seqmax = 1;
        PL_op = o;
        switch (o->op_type) {
        case OP_SETSTATE:
        case OP_NEXTSTATE:
        case OP_DBSTATE:
            PL_curcop = ((COP*)o);              /* for warnings */
            o->op_seq = PL_op_seqmax++;
            break;

        case OP_CONST:
            if (cSVOPo->op_private & OPpCONST_STRICT)
                no_bareword_allowed(o);
#ifdef USE_ITHREADS
        case OP_METHOD_NAMED:
            /* Relocate sv to the pad for thread safety.
             * Despite being a "constant", the SV is written to,
             * for reference counts, sv_upgrade() etc. */
            if (cSVOP->op_sv) {
                PADOFFSET ix = pad_alloc(OP_CONST, SVs_PADTMP);
                if (o->op_type == OP_CONST && SvPADTMP(cSVOPo->op_sv)) {
                    /* If op_sv is already a PADTMP then it is being used by
                     * some pad, so make a copy. */
                    sv_setsv(PAD_SVl(ix),cSVOPo->op_sv);
                    SvREADONLY_on(PAD_SVl(ix));
                    SvREFCNT_dec(cSVOPo->op_sv);
                }
                else {
                    SvREFCNT_dec(PAD_SVl(ix));
                    SvPADTMP_on(cSVOPo->op_sv);
                    PAD_SETSV(ix, cSVOPo->op_sv);
                    /* XXX I don't know how this isn't readonly already. */
                    SvREADONLY_on(PAD_SVl(ix));
                }
                cSVOPo->op_sv = Nullsv;
                o->op_targ = ix;
            }
#endif
            o->op_seq = PL_op_seqmax++;
            break;

        case OP_CONCAT:
            if (o->op_next && o->op_next->op_type == OP_STRINGIFY) {
                if (o->op_next->op_private & OPpTARGET_MY) {
                    if (o->op_flags & OPf_STACKED) /* chained concats */
                        goto ignore_optimization;
                    else {
                        /* assert(PL_opargs[o->op_type] & OA_TARGLEX); */
                        o->op_targ = o->op_next->op_targ;
                        o->op_next->op_targ = 0;
                        o->op_private |= OPpTARGET_MY;
                    }
                }
                op_null(o->op_next);
            }
          ignore_optimization:
            o->op_seq = PL_op_seqmax++;
            break;
        case OP_STUB:
            if ((o->op_flags & OPf_WANT) != OPf_WANT_LIST) {
                o->op_seq = PL_op_seqmax++;
                break; /* Scalar stub must produce undef.  List stub is noop */
            }
            goto nothin;
        case OP_NULL:
            if (o->op_targ == OP_NEXTSTATE
                || o->op_targ == OP_DBSTATE
                || o->op_targ == OP_SETSTATE)
            {
                PL_curcop = ((COP*)o);
            }
            /* XXX: We avoid setting op_seq here to prevent later calls
               to peep() from mistakenly concluding that optimisation
               has already occurred. This doesn't fix the real problem,
               though (See 20010220.007). AMS 20010719 */
            if (oldop && o->op_next) {
                oldop->op_next = o->op_next;
                continue;
            }
            break;
        case OP_SCALAR:
        case OP_LINESEQ:
        case OP_SCOPE:
          nothin:
            if (oldop && o->op_next) {
                oldop->op_next = o->op_next;
                continue;
            }
            o->op_seq = PL_op_seqmax++;
            break;

        case OP_PADAV:
        case OP_GV:
            if (o->op_type == OP_PADAV || o->op_next->op_type == OP_RV2AV) {
                OP* pop = (o->op_type == OP_PADAV) ?
                            o->op_next : o->op_next->op_next;
                IV i;
                if (pop && pop->op_type == OP_CONST &&
                    ((PL_op = pop->op_next)) &&
                    pop->op_next->op_type == OP_AELEM &&
                    !(pop->op_next->op_private &
                      (OPpLVAL_INTRO|OPpLVAL_DEFER|OPpDEREF|OPpMAYBE_LVSUB)) &&
                    (i = SvIV(((SVOP*)pop)->op_sv) - PL_curcop->cop_arybase)
                                <= 255 &&
                    i >= 0)
                {
                    GV *gv;
                    if (cSVOPx(pop)->op_private & OPpCONST_STRICT)
                        no_bareword_allowed(pop);
                    if (o->op_type == OP_GV)
                        op_null(o->op_next);
                    op_null(pop->op_next);
                    op_null(pop);
                    o->op_flags |= pop->op_next->op_flags & OPf_MOD;
                    o->op_next = pop->op_next->op_next;
                    o->op_ppaddr = PL_ppaddr[OP_AELEMFAST];
                    o->op_private = (U8)i;
                    if (o->op_type == OP_GV) {
                        gv = cGVOPo_gv;
                        GvAVn(gv);
                    }
                    else
                        o->op_flags |= OPf_SPECIAL;
                    o->op_type = OP_AELEMFAST;
                }
                o->op_seq = PL_op_seqmax++;
                break;
            }

            if (o->op_next->op_type == OP_RV2SV) {
                if (!(o->op_next->op_private & OPpDEREF)) {
                    op_null(o->op_next);
                    o->op_private |= o->op_next->op_private & (OPpLVAL_INTRO
                                                               | OPpOUR_INTRO);
                    o->op_next = o->op_next->op_next;
                    o->op_type = OP_GVSV;
                    o->op_ppaddr = PL_ppaddr[OP_GVSV];
                }
            }
            else if ((o->op_private & OPpEARLY_CV) && ckWARN(WARN_PROTOTYPE)) {
                GV *gv = cGVOPo_gv;
                if (SvTYPE(gv) == SVt_PVGV && GvCV(gv) && SvPVX(GvCV(gv))) {
                    /* XXX could check prototype here instead of just carping */
                    SV *sv = sv_newmortal();
                    gv_efullname3(sv, gv, Nullch);
                    Perl_warner(aTHX_ packWARN(WARN_PROTOTYPE),
                                "%"SVf"() called too early to check prototype",
                                sv);
                }
            }
            else if (o->op_next->op_type == OP_READLINE
                    && o->op_next->op_next->op_type == OP_CONCAT
                    && (o->op_next->op_next->op_flags & OPf_STACKED))
            {
                /* Turn "$a .= <FH>" into an OP_RCATLINE. AMS 20010917 */
                o->op_type   = OP_RCATLINE;
                o->op_flags |= OPf_STACKED;
                o->op_ppaddr = PL_ppaddr[OP_RCATLINE];
                op_null(o->op_next->op_next);
                op_null(o->op_next);
            }

            o->op_seq = PL_op_seqmax++;
            break;

        case OP_MAPWHILE:
        case OP_GREPWHILE:
        case OP_AND:
        case OP_OR:
        case OP_ANDASSIGN:
        case OP_ORASSIGN:
        case OP_COND_EXPR:
        case OP_RANGE:
            o->op_seq = PL_op_seqmax++;
            while (cLOGOP->op_other->op_type == OP_NULL)
                cLOGOP->op_other = cLOGOP->op_other->op_next;
            peep(cLOGOP->op_other); /* Recursive calls are not replaced by fptr calls */
            break;

        case OP_ENTERLOOP:
        case OP_ENTERITER:
            o->op_seq = PL_op_seqmax++;
            while (cLOOP->op_redoop->op_type == OP_NULL)
                cLOOP->op_redoop = cLOOP->op_redoop->op_next;
            peep(cLOOP->op_redoop);
            while (cLOOP->op_nextop->op_type == OP_NULL)
                cLOOP->op_nextop = cLOOP->op_nextop->op_next;
            peep(cLOOP->op_nextop);
            while (cLOOP->op_lastop->op_type == OP_NULL)
                cLOOP->op_lastop = cLOOP->op_lastop->op_next;
            peep(cLOOP->op_lastop);
            break;

        case OP_QR:
        case OP_MATCH:
        case OP_SUBST:
            o->op_seq = PL_op_seqmax++;
            while (cPMOP->op_pmreplstart &&
                   cPMOP->op_pmreplstart->op_type == OP_NULL)
                cPMOP->op_pmreplstart = cPMOP->op_pmreplstart->op_next;
            peep(cPMOP->op_pmreplstart);
            break;

        case OP_EXEC:
            o->op_seq = PL_op_seqmax++;
            if (ckWARN(WARN_SYNTAX) && o->op_next
                && o->op_next->op_type == OP_NEXTSTATE) {
                if (o->op_next->op_sibling &&
                        o->op_next->op_sibling->op_type != OP_EXIT &&
                        o->op_next->op_sibling->op_type != OP_WARN &&
                        o->op_next->op_sibling->op_type != OP_DIE) {
                    line_t oldline = CopLINE(PL_curcop);

                    CopLINE_set(PL_curcop, CopLINE((COP*)o->op_next));
                    Perl_warner(aTHX_ packWARN(WARN_EXEC),
                                "Statement unlikely to be reached");
                    Perl_warner(aTHX_ packWARN(WARN_EXEC),
                                "\t(Maybe you meant system() when you said exec()?)\n");
                    CopLINE_set(PL_curcop, oldline);
                }
            }
            break;

        case OP_HELEM: {
            UNOP *rop;
            SV *lexname;
            GV **fields;
            SV **svp, **indsvp, *sv;
            I32 ind;
            char *key = NULL;
            STRLEN keylen;

            o->op_seq = PL_op_seqmax++;

            if (((BINOP*)o)->op_last->op_type != OP_CONST)
                break;

            /* Make the CONST have a shared SV */
            svp = cSVOPx_svp(((BINOP*)o)->op_last);
            if ((!SvFAKE(sv = *svp) || !SvREADONLY(sv)) && !IS_PADCONST(sv)) {
                key = SvPV(sv, keylen);
                lexname = newSVpvn_share(key,
                                         SvUTF8(sv) ? -(I32)keylen : keylen,
                                         0);
                SvREFCNT_dec(sv);
                *svp = lexname;
            }

            if ((o->op_private & (OPpLVAL_INTRO)))
                break;

            rop = (UNOP*)((BINOP*)o)->op_first;
            if (rop->op_type != OP_RV2HV || rop->op_first->op_type != OP_PADSV)
                break;
            lexname = *av_fetch(PL_comppad_name, rop->op_first->op_targ, TRUE);
            if (!(SvFLAGS(lexname) & SVpad_TYPED))
                break;
            fields = (GV**)hv_fetch(SvSTASH(lexname), "FIELDS", 6, FALSE);
            if (!fields || !GvHV(*fields))
                break;
            key = SvPV(*svp, keylen);
            indsvp = hv_fetch(GvHV(*fields), key,
                              SvUTF8(*svp) ? -(I32)keylen : keylen, FALSE);
            if (!indsvp) {
                Perl_croak(aTHX_ "No such pseudo-hash field \"%s\" in variable %s of type %s",
                      key, SvPV(lexname, n_a), HvNAME(SvSTASH(lexname)));
            }
            ind = SvIV(*indsvp);
            if (ind < 1)
                Perl_croak(aTHX_ "Bad index while coercing array into hash");
            rop->op_type = OP_RV2AV;
            rop->op_ppaddr = PL_ppaddr[OP_RV2AV];
            o->op_type = OP_AELEM;
            o->op_ppaddr = PL_ppaddr[OP_AELEM];
            sv = newSViv(ind);
            if (SvREADONLY(*svp))
                SvREADONLY_on(sv);
            SvFLAGS(sv) |= (SvFLAGS(*svp)
                            & (SVs_PADBUSY|SVs_PADTMP|SVs_PADMY));
            SvREFCNT_dec(*svp);
            *svp = sv;
            break;
        }

        case OP_HSLICE: {
            UNOP *rop;
            SV *lexname;
            GV **fields;
            SV **svp, **indsvp, *sv;
            I32 ind;
            char *key;
            STRLEN keylen;
            SVOP *first_key_op, *key_op;

            o->op_seq = PL_op_seqmax++;
            if ((o->op_private & (OPpLVAL_INTRO))
                /* I bet there's always a pushmark... */
                || ((LISTOP*)o)->op_first->op_sibling->op_type != OP_LIST)
                /* hmmm, no optimization if list contains only one key. */
                break;
            rop = (UNOP*)((LISTOP*)o)->op_last;
            if (rop->op_type != OP_RV2HV || rop->op_first->op_type != OP_PADSV)
                break;
            lexname = *av_fetch(PL_comppad_name, rop->op_first->op_targ, TRUE);
            if (!(SvFLAGS(lexname) & SVpad_TYPED))
                break;
            fields = (GV**)hv_fetch(SvSTASH(lexname), "FIELDS", 6, FALSE);
            if (!fields || !GvHV(*fields))
                break;
            /* Again guessing that the pushmark can be jumped over.... */
            first_key_op = (SVOP*)((LISTOP*)((LISTOP*)o)->op_first->op_sibling)
                ->op_first->op_sibling;
            /* Check that the key list contains only constants. */
            for (key_op = first_key_op; key_op;
                 key_op = (SVOP*)key_op->op_sibling)
                if (key_op->op_type != OP_CONST)
                    break;
            if (key_op)
                break;
            rop->op_type = OP_RV2AV;
            rop->op_ppaddr = PL_ppaddr[OP_RV2AV];
            o->op_type = OP_ASLICE;
            o->op_ppaddr = PL_ppaddr[OP_ASLICE];
            for (key_op = first_key_op; key_op;
                 key_op = (SVOP*)key_op->op_sibling) {
                svp = cSVOPx_svp(key_op);
                key = SvPV(*svp, keylen);
                indsvp = hv_fetch(GvHV(*fields), key,
                                  SvUTF8(*svp) ? -(I32)keylen : keylen, FALSE);
                if (!indsvp) {
                    Perl_croak(aTHX_ "No such pseudo-hash field \"%s\" "
                               "in variable %s of type %s",
                          key, SvPV(lexname, n_a), HvNAME(SvSTASH(lexname)));
                }
                ind = SvIV(*indsvp);
                if (ind < 1)
                    Perl_croak(aTHX_ "Bad index while coercing array into hash");
                sv = newSViv(ind);
                if (SvREADONLY(*svp))
                    SvREADONLY_on(sv);
                SvFLAGS(sv) |= (SvFLAGS(*svp)
                                & (SVs_PADBUSY|SVs_PADTMP|SVs_PADMY));
                SvREFCNT_dec(*svp);
                *svp = sv;
            }
            break;
        }

        case OP_SORT: {
            /* will point to RV2AV or PADAV op on LHS/RHS of assign */
            OP *oleft, *oright;
            OP *o2;

            /* check that RHS of sort is a single plain array */
            oright = cUNOPo->op_first;
            if (!oright || oright->op_type != OP_PUSHMARK)
                break;

            /* reverse sort ... can be optimised.  */
            if (!cUNOPo->op_sibling) {
                /* Nothing follows us on the list. */
                OP *reverse = o->op_next;

                if (reverse->op_type == OP_REVERSE &&
                    (reverse->op_flags & OPf_WANT) == OPf_WANT_LIST) {
                    OP *pushmark = cUNOPx(reverse)->op_first;
                    if (pushmark && (pushmark->op_type == OP_PUSHMARK)
                        && (cUNOPx(pushmark)->op_sibling == o)) {
                        /* reverse -> pushmark -> sort */
                        o->op_private |= OPpSORT_REVERSE;
                        op_null(reverse);
                        pushmark->op_next = oright->op_next;
                        op_null(oright);
                    }
                }
            }

            /* make @a = sort @a act in-place */

            o->op_seq = PL_op_seqmax++;

            oright = cUNOPx(oright)->op_sibling;
            if (!oright)
                break;
            if (oright->op_type == OP_NULL) { /* skip sort block/sub */
                oright = cUNOPx(oright)->op_sibling;
            }

            if (!oright ||
                (oright->op_type != OP_RV2AV && oright->op_type != OP_PADAV)
                || oright->op_next != o
                || (oright->op_private & OPpLVAL_INTRO)
            )
                break;

            /* o2 follows the chain of op_nexts through the LHS of the
             * assign (if any) to the aassign op itself */
            o2 = o->op_next;
            if (!o2 || o2->op_type != OP_NULL)
                break;
            o2 = o2->op_next;
            if (!o2 || o2->op_type != OP_PUSHMARK)
                break;
            o2 = o2->op_next;
            if (o2 && o2->op_type == OP_GV)
                o2 = o2->op_next;
            if (!o2
                || (o2->op_type != OP_PADAV && o2->op_type != OP_RV2AV)
                || (o2->op_private & OPpLVAL_INTRO)
            )
                break;
            oleft = o2;
            o2 = o2->op_next;
            if (!o2 || o2->op_type != OP_NULL)
                break;
            o2 = o2->op_next;
            if (!o2 || o2->op_type != OP_AASSIGN
                    || (o2->op_flags & OPf_WANT) != OPf_WANT_VOID)
                break;

            /* check that the sort is the first arg on RHS of assign */

            o2 = cUNOPx(o2)->op_first;
            if (!o2 || o2->op_type != OP_NULL)
                break;
            o2 = cUNOPx(o2)->op_first;
            if (!o2 || o2->op_type != OP_PUSHMARK)
                break;
            if (o2->op_sibling != o)
                break;

            /* check the array is the same on both sides */
            if (oleft->op_type == OP_RV2AV) {
                if (oright->op_type != OP_RV2AV
                    || !cUNOPx(oright)->op_first
                    || cUNOPx(oright)->op_first->op_type != OP_GV
                    ||  cGVOPx_gv(cUNOPx(oleft)->op_first) !=
                        cGVOPx_gv(cUNOPx(oright)->op_first)
                )
                    break;
            }
            else if (oright->op_type != OP_PADAV
                || oright->op_targ != oleft->op_targ
            )
                break;

            /* transfer MODishness etc from LHS arg to RHS arg */
            oright->op_flags = oleft->op_flags;
            o->op_private |= OPpSORT_INPLACE;

            /* excise push->gv->rv2av->null->aassign */
            o2 = o->op_next->op_next;
            op_null(o2); /* PUSHMARK */
            o2 = o2->op_next;
            if (o2->op_type == OP_GV) {
                op_null(o2); /* GV */
                o2 = o2->op_next;
            }
            op_null(o2); /* RV2AV or PADAV */
            o2 = o2->op_next->op_next;
            op_null(o2); /* AASSIGN */

            o->op_next = o2->op_next;

            break;
        }

        case OP_REVERSE: {
            OP *ourmark, *theirmark, *ourlast, *iter, *expushmark, *rv2av;
            OP *gvop = NULL;
            LISTOP *enter, *exlist;
            o->op_seq = PL_op_seqmax++;

            enter = (LISTOP *) o->op_next;
            if (!enter)
                break;
            if (enter->op_type == OP_NULL) {
                enter = (LISTOP *) enter->op_next;
                if (!enter)
                    break;
            }
            /* for $a (...) will have OP_GV then OP_RV2GV here.
               for (...) just has an OP_GV.  */
            if (enter->op_type == OP_GV) {
                gvop = (OP *) enter;
                enter = (LISTOP *) enter->op_next;
                if (!enter)
                    break;
                if (enter->op_type == OP_RV2GV) {
                  enter = (LISTOP *) enter->op_next;
                  if (!enter)
                    break;
                }
            }

            if (enter->op_type != OP_ENTERITER)
                break;

            iter = enter->op_next;
            if (!iter || iter->op_type != OP_ITER)
                break;
            
            expushmark = enter->op_first;
            if (!expushmark || expushmark->op_type != OP_NULL
                || expushmark->op_targ != OP_PUSHMARK)
                break;

            exlist = (LISTOP *) expushmark->op_sibling;
            if (!exlist || exlist->op_type != OP_NULL
                || exlist->op_targ != OP_LIST)
                break;

            if (exlist->op_last != o) {
                /* Mmm. Was expecting to point back to this op.  */
                break;
            }
            theirmark = exlist->op_first;
            if (!theirmark || theirmark->op_type != OP_PUSHMARK)
                break;

            if (theirmark->op_sibling != o) {
                /* There's something between the mark and the reverse, eg
                   for (1, reverse (...))
                   so no go.  */
                break;
            }

            ourmark = ((LISTOP *)o)->op_first;
            if (!ourmark || ourmark->op_type != OP_PUSHMARK)
                break;

            ourlast = ((LISTOP *)o)->op_last;
            if (!ourlast || ourlast->op_next != o)
                break;

            rv2av = ourmark->op_sibling;
            if (rv2av && rv2av->op_type == OP_RV2AV && rv2av->op_sibling == 0
                && rv2av->op_flags == (OPf_WANT_LIST | OPf_KIDS)
                && enter->op_flags == (OPf_WANT_LIST | OPf_KIDS)) {
                /* We're just reversing a single array.  */
                rv2av->op_flags = OPf_WANT_SCALAR | OPf_KIDS | OPf_REF;
                enter->op_flags |= OPf_STACKED;
            }

            /* We don't have control over who points to theirmark, so sacrifice
               ours.  */
            theirmark->op_next = ourmark->op_next;
            theirmark->op_flags = ourmark->op_flags;
            ourlast->op_next = gvop ? gvop : (OP *) enter;
            op_null(ourmark);
            op_null(o);
            enter->op_private |= OPpITER_REVERSED;
            iter->op_private |= OPpITER_REVERSED;
            
            break;
        }
        
        default:
            o->op_seq = PL_op_seqmax++;
            break;
        }
        oldop = o;
    }
    LEAVE;
}


char* Perl_custom_op_name(pTHX_ OP* o)
{
    IV  index = PTR2IV(o->op_ppaddr);
    SV* keysv;
    HE* he;

    if (!PL_custom_op_names) /* This probably shouldn't happen */
        return PL_op_name[OP_CUSTOM];

    keysv = sv_2mortal(newSViv(index));

    he = hv_fetch_ent(PL_custom_op_names, keysv, 0, 0);
    if (!he)
        return PL_op_name[OP_CUSTOM]; /* Don't know who you are */

    return SvPV_nolen(HeVAL(he));
}

char* Perl_custom_op_desc(pTHX_ OP* o)
{
    IV  index = PTR2IV(o->op_ppaddr);
    SV* keysv;
    HE* he;

    if (!PL_custom_op_descs)
        return PL_op_desc[OP_CUSTOM];

    keysv = sv_2mortal(newSViv(index));

    he = hv_fetch_ent(PL_custom_op_descs, keysv, 0, 0);
    if (!he)
        return PL_op_desc[OP_CUSTOM];

    return SvPV_nolen(HeVAL(he));
}


#include "XSUB.h"

/* Efficient sub that returns a constant scalar value. */
static void
const_sv_xsub(pTHX_ CV* cv)
{
    dXSARGS;
    if (items != 0) {
#if 0
        Perl_croak(aTHX_ "usage: %s::%s()",
                   HvNAME(GvSTASH(CvGV(cv))), GvNAME(CvGV(cv)));
#endif
    }
    EXTEND(sp, 1);
    ST(0) = (SV*)XSANY.any_ptr;
    XSRETURN(1);
}
Revision:	1.1
Committed:	Thu Jun 30 14:26:42 2005 UTC (21 years, 3 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *