| 1 |
/* alloca.c -- allocate automatically reclaimed memory |
| 2 |
(Mostly) portable public-domain implementation -- D A Gwyn |
| 3 |
|
| 4 |
This implementation of the PWB library alloca function, |
| 5 |
which is used to allocate space off the run-time stack so |
| 6 |
that it is automatically reclaimed upon procedure exit, |
| 7 |
was inspired by discussions with J. Q. Johnson of Cornell. |
| 8 |
J.Otto Tennant <jot@cray.com> contributed the Cray support. |
| 9 |
|
| 10 |
There are some preprocessor constants that can |
| 11 |
be defined when compiling for your specific system, for |
| 12 |
improved efficiency; however, the defaults should be okay. |
| 13 |
|
| 14 |
The general concept of this implementation is to keep |
| 15 |
track of all alloca-allocated blocks, and reclaim any |
| 16 |
that are found to be deeper in the stack than the current |
| 17 |
invocation. This heuristic does not reclaim storage as |
| 18 |
soon as it becomes invalid, but it will do so eventually. |
| 19 |
|
| 20 |
As a special case, alloca(0) reclaims storage without |
| 21 |
allocating any. It is a good idea to use alloca(0) in |
| 22 |
your main control loop, etc. to force garbage collection. */ |
| 23 |
|
| 24 |
#ifdef HAVE_CONFIG_H |
| 25 |
# include <config.h> |
| 26 |
#endif |
| 27 |
|
| 28 |
#ifdef emacs |
| 29 |
# include "blockinput.h" |
| 30 |
#endif |
| 31 |
|
| 32 |
/* If compiling with GCC 2, this file's not needed. */ |
| 33 |
#if !defined (__GNUC__) || __GNUC__ < 2 |
| 34 |
|
| 35 |
/* If someone has defined alloca as a macro, |
| 36 |
there must be some other way alloca is supposed to work. */ |
| 37 |
# ifndef alloca |
| 38 |
|
| 39 |
# ifdef emacs |
| 40 |
# ifdef static |
| 41 |
/* actually, only want this if static is defined as "" |
| 42 |
-- this is for usg, in which emacs must undefine static |
| 43 |
in order to make unexec workable |
| 44 |
*/ |
| 45 |
# ifndef STACK_DIRECTION |
| 46 |
you |
| 47 |
lose |
| 48 |
-- must know STACK_DIRECTION at compile-time |
| 49 |
# endif /* STACK_DIRECTION undefined */ |
| 50 |
# endif /* static */ |
| 51 |
# endif /* emacs */ |
| 52 |
|
| 53 |
/* If your stack is a linked list of frames, you have to |
| 54 |
provide an "address metric" ADDRESS_FUNCTION macro. */ |
| 55 |
|
| 56 |
# if defined (CRAY) && defined (CRAY_STACKSEG_END) |
| 57 |
long i00afunc (); |
| 58 |
# define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) |
| 59 |
# else |
| 60 |
# define ADDRESS_FUNCTION(arg) &(arg) |
| 61 |
# endif |
| 62 |
|
| 63 |
# if __STDC__ |
| 64 |
typedef void *pointer; |
| 65 |
# else |
| 66 |
typedef char *pointer; |
| 67 |
# endif |
| 68 |
|
| 69 |
# ifndef NULL |
| 70 |
# define NULL 0 |
| 71 |
# endif |
| 72 |
|
| 73 |
/* Different portions of Emacs need to call different versions of |
| 74 |
malloc. The Emacs executable needs alloca to call xmalloc, because |
| 75 |
ordinary malloc isn't protected from input signals. On the other |
| 76 |
hand, the utilities in lib-src need alloca to call malloc; some of |
| 77 |
them are very simple, and don't have an xmalloc routine. |
| 78 |
|
| 79 |
Non-Emacs programs expect this to call xmalloc. |
| 80 |
|
| 81 |
Callers below should use malloc. */ |
| 82 |
|
| 83 |
# ifndef emacs |
| 84 |
# define malloc xmalloc |
| 85 |
# endif |
| 86 |
extern pointer malloc (); |
| 87 |
|
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/* Define STACK_DIRECTION if you know the direction of stack |
| 89 |
growth for your system; otherwise it will be automatically |
| 90 |
deduced at run-time. |
| 91 |
|
| 92 |
STACK_DIRECTION > 0 => grows toward higher addresses |
| 93 |
STACK_DIRECTION < 0 => grows toward lower addresses |
| 94 |
STACK_DIRECTION = 0 => direction of growth unknown */ |
| 95 |
|
| 96 |
# ifndef STACK_DIRECTION |
| 97 |
# define STACK_DIRECTION 0 /* Direction unknown. */ |
| 98 |
# endif |
| 99 |
|
| 100 |
# if STACK_DIRECTION != 0 |
| 101 |
|
| 102 |
# define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ |
| 103 |
|
| 104 |
# else /* STACK_DIRECTION == 0; need run-time code. */ |
| 105 |
|
| 106 |
static int stack_dir; /* 1 or -1 once known. */ |
| 107 |
# define STACK_DIR stack_dir |
| 108 |
|
| 109 |
static void |
| 110 |
find_stack_direction () |
| 111 |
{ |
| 112 |
static char *addr = NULL; /* Address of first `dummy', once known. */ |
| 113 |
auto char dummy; /* To get stack address. */ |
| 114 |
|
| 115 |
if (addr == NULL) |
| 116 |
{ /* Initial entry. */ |
| 117 |
addr = ADDRESS_FUNCTION (dummy); |
| 118 |
|
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find_stack_direction (); /* Recurse once. */ |
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} |
| 121 |
else |
| 122 |
{ |
| 123 |
/* Second entry. */ |
| 124 |
if (ADDRESS_FUNCTION (dummy) > addr) |
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stack_dir = 1; /* Stack grew upward. */ |
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else |
| 127 |
stack_dir = -1; /* Stack grew downward. */ |
| 128 |
} |
| 129 |
} |
| 130 |
|
| 131 |
# endif /* STACK_DIRECTION == 0 */ |
| 132 |
|
| 133 |
/* An "alloca header" is used to: |
| 134 |
(a) chain together all alloca'ed blocks; |
| 135 |
(b) keep track of stack depth. |
| 136 |
|
| 137 |
It is very important that sizeof(header) agree with malloc |
| 138 |
alignment chunk size. The following default should work okay. */ |
| 139 |
|
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# ifndef ALIGN_SIZE |
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# define ALIGN_SIZE sizeof(double) |
| 142 |
# endif |
| 143 |
|
| 144 |
typedef union hdr |
| 145 |
{ |
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char align[ALIGN_SIZE]; /* To force sizeof(header). */ |
| 147 |
struct |
| 148 |
{ |
| 149 |
union hdr *next; /* For chaining headers. */ |
| 150 |
char *deep; /* For stack depth measure. */ |
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} h; |
| 152 |
} header; |
| 153 |
|
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static header *last_alloca_header = NULL; /* -> last alloca header. */ |
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|
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/* Return a pointer to at least SIZE bytes of storage, |
| 157 |
which will be automatically reclaimed upon exit from |
| 158 |
the procedure that called alloca. Originally, this space |
| 159 |
was supposed to be taken from the current stack frame of the |
| 160 |
caller, but that method cannot be made to work for some |
| 161 |
implementations of C, for example under Gould's UTX/32. */ |
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|
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pointer |
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alloca (size) |
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unsigned size; |
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{ |
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auto char probe; /* Probes stack depth: */ |
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register char *depth = ADDRESS_FUNCTION (probe); |
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|
| 170 |
# if STACK_DIRECTION == 0 |
| 171 |
if (STACK_DIR == 0) /* Unknown growth direction. */ |
| 172 |
find_stack_direction (); |
| 173 |
# endif |
| 174 |
|
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/* Reclaim garbage, defined as all alloca'd storage that |
| 176 |
was allocated from deeper in the stack than currently. */ |
| 177 |
|
| 178 |
{ |
| 179 |
register header *hp; /* Traverses linked list. */ |
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|
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# ifdef emacs |
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BLOCK_INPUT; |
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# endif |
| 184 |
|
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for (hp = last_alloca_header; hp != NULL;) |
| 186 |
if ((STACK_DIR > 0 && hp->h.deep > depth) |
| 187 |
|| (STACK_DIR < 0 && hp->h.deep < depth)) |
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{ |
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register header *np = hp->h.next; |
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|
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free ((pointer) hp); /* Collect garbage. */ |
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|
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hp = np; /* -> next header. */ |
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} |
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else |
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break; /* Rest are not deeper. */ |
| 197 |
|
| 198 |
last_alloca_header = hp; /* -> last valid storage. */ |
| 199 |
|
| 200 |
# ifdef emacs |
| 201 |
UNBLOCK_INPUT; |
| 202 |
# endif |
| 203 |
} |
| 204 |
|
| 205 |
if (size == 0) |
| 206 |
return NULL; /* No allocation required. */ |
| 207 |
|
| 208 |
/* Allocate combined header + user data storage. */ |
| 209 |
|
| 210 |
{ |
| 211 |
register pointer new = malloc (sizeof (header) + size); |
| 212 |
/* Address of header. */ |
| 213 |
|
| 214 |
((header *) new)->h.next = last_alloca_header; |
| 215 |
((header *) new)->h.deep = depth; |
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|
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last_alloca_header = (header *) new; |
| 218 |
|
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/* User storage begins just after header. */ |
| 220 |
|
| 221 |
return (pointer) ((char *) new + sizeof (header)); |
| 222 |
} |
| 223 |
} |
| 224 |
|
| 225 |
# if defined (CRAY) && defined (CRAY_STACKSEG_END) |
| 226 |
|
| 227 |
# ifdef DEBUG_I00AFUNC |
| 228 |
# include <stdio.h> |
| 229 |
# endif |
| 230 |
|
| 231 |
# ifndef CRAY_STACK |
| 232 |
# define CRAY_STACK |
| 233 |
# ifndef CRAY2 |
| 234 |
/* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ |
| 235 |
struct stack_control_header |
| 236 |
{ |
| 237 |
long shgrow:32; /* Number of times stack has grown. */ |
| 238 |
long shaseg:32; /* Size of increments to stack. */ |
| 239 |
long shhwm:32; /* High water mark of stack. */ |
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long shsize:32; /* Current size of stack (all segments). */ |
| 241 |
}; |
| 242 |
|
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/* The stack segment linkage control information occurs at |
| 244 |
the high-address end of a stack segment. (The stack |
| 245 |
grows from low addresses to high addresses.) The initial |
| 246 |
part of the stack segment linkage control information is |
| 247 |
0200 (octal) words. This provides for register storage |
| 248 |
for the routine which overflows the stack. */ |
| 249 |
|
| 250 |
struct stack_segment_linkage |
| 251 |
{ |
| 252 |
long ss[0200]; /* 0200 overflow words. */ |
| 253 |
long sssize:32; /* Number of words in this segment. */ |
| 254 |
long ssbase:32; /* Offset to stack base. */ |
| 255 |
long:32; |
| 256 |
long sspseg:32; /* Offset to linkage control of previous |
| 257 |
segment of stack. */ |
| 258 |
long:32; |
| 259 |
long sstcpt:32; /* Pointer to task common address block. */ |
| 260 |
long sscsnm; /* Private control structure number for |
| 261 |
microtasking. */ |
| 262 |
long ssusr1; /* Reserved for user. */ |
| 263 |
long ssusr2; /* Reserved for user. */ |
| 264 |
long sstpid; /* Process ID for pid based multi-tasking. */ |
| 265 |
long ssgvup; /* Pointer to multitasking thread giveup. */ |
| 266 |
long sscray[7]; /* Reserved for Cray Research. */ |
| 267 |
long ssa0; |
| 268 |
long ssa1; |
| 269 |
long ssa2; |
| 270 |
long ssa3; |
| 271 |
long ssa4; |
| 272 |
long ssa5; |
| 273 |
long ssa6; |
| 274 |
long ssa7; |
| 275 |
long sss0; |
| 276 |
long sss1; |
| 277 |
long sss2; |
| 278 |
long sss3; |
| 279 |
long sss4; |
| 280 |
long sss5; |
| 281 |
long sss6; |
| 282 |
long sss7; |
| 283 |
}; |
| 284 |
|
| 285 |
# else /* CRAY2 */ |
| 286 |
/* The following structure defines the vector of words |
| 287 |
returned by the STKSTAT library routine. */ |
| 288 |
struct stk_stat |
| 289 |
{ |
| 290 |
long now; /* Current total stack size. */ |
| 291 |
long maxc; /* Amount of contiguous space which would |
| 292 |
be required to satisfy the maximum |
| 293 |
stack demand to date. */ |
| 294 |
long high_water; /* Stack high-water mark. */ |
| 295 |
long overflows; /* Number of stack overflow ($STKOFEN) calls. */ |
| 296 |
long hits; /* Number of internal buffer hits. */ |
| 297 |
long extends; /* Number of block extensions. */ |
| 298 |
long stko_mallocs; /* Block allocations by $STKOFEN. */ |
| 299 |
long underflows; /* Number of stack underflow calls ($STKRETN). */ |
| 300 |
long stko_free; /* Number of deallocations by $STKRETN. */ |
| 301 |
long stkm_free; /* Number of deallocations by $STKMRET. */ |
| 302 |
long segments; /* Current number of stack segments. */ |
| 303 |
long maxs; /* Maximum number of stack segments so far. */ |
| 304 |
long pad_size; /* Stack pad size. */ |
| 305 |
long current_address; /* Current stack segment address. */ |
| 306 |
long current_size; /* Current stack segment size. This |
| 307 |
number is actually corrupted by STKSTAT to |
| 308 |
include the fifteen word trailer area. */ |
| 309 |
long initial_address; /* Address of initial segment. */ |
| 310 |
long initial_size; /* Size of initial segment. */ |
| 311 |
}; |
| 312 |
|
| 313 |
/* The following structure describes the data structure which trails |
| 314 |
any stack segment. I think that the description in 'asdef' is |
| 315 |
out of date. I only describe the parts that I am sure about. */ |
| 316 |
|
| 317 |
struct stk_trailer |
| 318 |
{ |
| 319 |
long this_address; /* Address of this block. */ |
| 320 |
long this_size; /* Size of this block (does not include |
| 321 |
this trailer). */ |
| 322 |
long unknown2; |
| 323 |
long unknown3; |
| 324 |
long link; /* Address of trailer block of previous |
| 325 |
segment. */ |
| 326 |
long unknown5; |
| 327 |
long unknown6; |
| 328 |
long unknown7; |
| 329 |
long unknown8; |
| 330 |
long unknown9; |
| 331 |
long unknown10; |
| 332 |
long unknown11; |
| 333 |
long unknown12; |
| 334 |
long unknown13; |
| 335 |
long unknown14; |
| 336 |
}; |
| 337 |
|
| 338 |
# endif /* CRAY2 */ |
| 339 |
# endif /* not CRAY_STACK */ |
| 340 |
|
| 341 |
# ifdef CRAY2 |
| 342 |
/* Determine a "stack measure" for an arbitrary ADDRESS. |
| 343 |
I doubt that "lint" will like this much. */ |
| 344 |
|
| 345 |
static long |
| 346 |
i00afunc (long *address) |
| 347 |
{ |
| 348 |
struct stk_stat status; |
| 349 |
struct stk_trailer *trailer; |
| 350 |
long *block, size; |
| 351 |
long result = 0; |
| 352 |
|
| 353 |
/* We want to iterate through all of the segments. The first |
| 354 |
step is to get the stack status structure. We could do this |
| 355 |
more quickly and more directly, perhaps, by referencing the |
| 356 |
$LM00 common block, but I know that this works. */ |
| 357 |
|
| 358 |
STKSTAT (&status); |
| 359 |
|
| 360 |
/* Set up the iteration. */ |
| 361 |
|
| 362 |
trailer = (struct stk_trailer *) (status.current_address |
| 363 |
+ status.current_size |
| 364 |
- 15); |
| 365 |
|
| 366 |
/* There must be at least one stack segment. Therefore it is |
| 367 |
a fatal error if "trailer" is null. */ |
| 368 |
|
| 369 |
if (trailer == 0) |
| 370 |
abort (); |
| 371 |
|
| 372 |
/* Discard segments that do not contain our argument address. */ |
| 373 |
|
| 374 |
while (trailer != 0) |
| 375 |
{ |
| 376 |
block = (long *) trailer->this_address; |
| 377 |
size = trailer->this_size; |
| 378 |
if (block == 0 || size == 0) |
| 379 |
abort (); |
| 380 |
trailer = (struct stk_trailer *) trailer->link; |
| 381 |
if ((block <= address) && (address < (block + size))) |
| 382 |
break; |
| 383 |
} |
| 384 |
|
| 385 |
/* Set the result to the offset in this segment and add the sizes |
| 386 |
of all predecessor segments. */ |
| 387 |
|
| 388 |
result = address - block; |
| 389 |
|
| 390 |
if (trailer == 0) |
| 391 |
{ |
| 392 |
return result; |
| 393 |
} |
| 394 |
|
| 395 |
do |
| 396 |
{ |
| 397 |
if (trailer->this_size <= 0) |
| 398 |
abort (); |
| 399 |
result += trailer->this_size; |
| 400 |
trailer = (struct stk_trailer *) trailer->link; |
| 401 |
} |
| 402 |
while (trailer != 0); |
| 403 |
|
| 404 |
/* We are done. Note that if you present a bogus address (one |
| 405 |
not in any segment), you will get a different number back, formed |
| 406 |
from subtracting the address of the first block. This is probably |
| 407 |
not what you want. */ |
| 408 |
|
| 409 |
return (result); |
| 410 |
} |
| 411 |
|
| 412 |
# else /* not CRAY2 */ |
| 413 |
/* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. |
| 414 |
Determine the number of the cell within the stack, |
| 415 |
given the address of the cell. The purpose of this |
| 416 |
routine is to linearize, in some sense, stack addresses |
| 417 |
for alloca. */ |
| 418 |
|
| 419 |
static long |
| 420 |
i00afunc (long address) |
| 421 |
{ |
| 422 |
long stkl = 0; |
| 423 |
|
| 424 |
long size, pseg, this_segment, stack; |
| 425 |
long result = 0; |
| 426 |
|
| 427 |
struct stack_segment_linkage *ssptr; |
| 428 |
|
| 429 |
/* Register B67 contains the address of the end of the |
| 430 |
current stack segment. If you (as a subprogram) store |
| 431 |
your registers on the stack and find that you are past |
| 432 |
the contents of B67, you have overflowed the segment. |
| 433 |
|
| 434 |
B67 also points to the stack segment linkage control |
| 435 |
area, which is what we are really interested in. */ |
| 436 |
|
| 437 |
stkl = CRAY_STACKSEG_END (); |
| 438 |
ssptr = (struct stack_segment_linkage *) stkl; |
| 439 |
|
| 440 |
/* If one subtracts 'size' from the end of the segment, |
| 441 |
one has the address of the first word of the segment. |
| 442 |
|
| 443 |
If this is not the first segment, 'pseg' will be |
| 444 |
nonzero. */ |
| 445 |
|
| 446 |
pseg = ssptr->sspseg; |
| 447 |
size = ssptr->sssize; |
| 448 |
|
| 449 |
this_segment = stkl - size; |
| 450 |
|
| 451 |
/* It is possible that calling this routine itself caused |
| 452 |
a stack overflow. Discard stack segments which do not |
| 453 |
contain the target address. */ |
| 454 |
|
| 455 |
while (!(this_segment <= address && address <= stkl)) |
| 456 |
{ |
| 457 |
# ifdef DEBUG_I00AFUNC |
| 458 |
fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); |
| 459 |
# endif |
| 460 |
if (pseg == 0) |
| 461 |
break; |
| 462 |
stkl = stkl - pseg; |
| 463 |
ssptr = (struct stack_segment_linkage *) stkl; |
| 464 |
size = ssptr->sssize; |
| 465 |
pseg = ssptr->sspseg; |
| 466 |
this_segment = stkl - size; |
| 467 |
} |
| 468 |
|
| 469 |
result = address - this_segment; |
| 470 |
|
| 471 |
/* If you subtract pseg from the current end of the stack, |
| 472 |
you get the address of the previous stack segment's end. |
| 473 |
This seems a little convoluted to me, but I'll bet you save |
| 474 |
a cycle somewhere. */ |
| 475 |
|
| 476 |
while (pseg != 0) |
| 477 |
{ |
| 478 |
# ifdef DEBUG_I00AFUNC |
| 479 |
fprintf (stderr, "%011o %011o\n", pseg, size); |
| 480 |
# endif |
| 481 |
stkl = stkl - pseg; |
| 482 |
ssptr = (struct stack_segment_linkage *) stkl; |
| 483 |
size = ssptr->sssize; |
| 484 |
pseg = ssptr->sspseg; |
| 485 |
result += size; |
| 486 |
} |
| 487 |
return (result); |
| 488 |
} |
| 489 |
|
| 490 |
# endif /* not CRAY2 */ |
| 491 |
# endif /* CRAY */ |
| 492 |
|
| 493 |
# endif /* no alloca */ |
| 494 |
#endif /* not GCC version 2 */ |
