libcoro/coro.h

/*
 * Copyright (c) 2001-2012,2015 Marc Alexander Lehmann <schmorp@schmorp.de>
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 *
 * This library is modelled strictly after Ralf S. Engelschalls article at
 * http://www.gnu.org/software/pth/rse-pmt.ps. So most of the credit must
 * go to Ralf S. Engelschall <rse@engelschall.com>.
 *
 * This coroutine library is very much stripped down. You should either
 * build your own process abstraction using it or - better - just use GNU
 * Portable Threads, http://www.gnu.org/software/pth/.
 *
 */

/*
 * 2006-10-26 Include stddef.h on OS X to work around one of its bugs.
 *            Reported by Michael_G_Schwern.
 * 2006-11-26 Use _setjmp instead of setjmp on GNU/Linux.
 * 2007-04-27 Set unwind frame info if gcc 3+ and ELF is detected.
 *            Use _setjmp instead of setjmp on _XOPEN_SOURCE >= 600.
 * 2007-05-02 Add assembly versions for x86 and amd64 (to avoid reliance
 *            on SIGUSR2 and sigaltstack in Crossfire).
 * 2008-01-21 Disable CFI usage on anything but GNU/Linux.
 * 2008-03-02 Switched to 2-clause BSD license with GPL exception.
 * 2008-04-04 New (but highly unrecommended) pthreads backend.
 * 2008-04-24 Reinstate CORO_LOSER (had wrong stack adjustments).
 * 2008-10-30 Support assembly method on x86 with and without frame pointer.
 * 2008-11-03 Use a global asm statement for CORO_ASM, idea by pippijn.
 * 2008-11-05 Hopefully fix misaligned stacks with CORO_ASM/SETJMP.
 * 2008-11-07 rbp wasn't saved in CORO_ASM on x86_64.
 *            introduce coro_destroy, which is a nop except for pthreads.
 *            speed up CORO_PTHREAD. Do no longer leak threads either.
 *            coro_create now allows one to create source coro_contexts.
 *            do not rely on makecontext passing a void * correctly.
 *            try harder to get _setjmp/_longjmp.
 *            major code cleanup/restructuring.
 * 2008-11-10 the .cfi hacks are no longer needed.
 * 2008-11-16 work around a freebsd pthread bug.
 * 2008-11-19 define coro_*jmp symbols for easier porting.
 * 2009-06-23 tentative win32-backend support for mingw32 (Yasuhiro Matsumoto).
 * 2010-12-03 tentative support for uclibc (which lacks all sorts of things).
 * 2011-05-30 set initial callee-saved-registers to zero with CORO_ASM.
 *            use .cfi_undefined rip on linux-amd64 for better backtraces.
 * 2011-06-08 maybe properly implement weird windows amd64 calling conventions.
 * 2011-07-03 rely on __GCC_HAVE_DWARF2_CFI_ASM for cfi detection.
 * 2011-08-08 cygwin trashes stacks, use pthreads with double stack on cygwin.
 * 2012-12-04 reduce misprediction penalty for x86/amd64 assembly switcher.
 * 2012-12-05 experimental fiber backend (allocates stack twice).
 * 2012-12-07 API version 3 - add coro_stack_alloc/coro_stack_free.
 * 2012-12-21 valgrind stack registering was broken.
 * 2015-12-05 experimental asm be for arm7, based on a patch by Nick Zavaritsky.
 *            use __name__ for predefined symbols, as in libecb.
 *            enable guard pages on arm, aarch64 and mips.
 * 2016-08-27 try to disable _FORTIFY_SOURCE with CORO_SJLJ, as it
 *            breaks setjmp/longjmp. Also disable CORO_ASM for asm by default,
 *            as it was reported to crash.
 */

#ifndef CORO_H
#define CORO_H

#if __cplusplus
extern "C" {
#endif

/*
 * This library consists of only three files
 * coro.h, coro.c and LICENSE (and optionally README)
 *
 * It implements what is known as coroutines, in a hopefully
 * portable way.
 *
 * All compiletime symbols must be defined both when including coro.h
 * (using libcoro) as well as when compiling coro.c (the implementation).
 *
 * You can manually specify which flavour you want. If you don't define
 * any of these, libcoro tries to choose a safe and fast default:
 *
 * -DCORO_UCONTEXT
 *
 *    This flavour uses SUSv2's get/set/swap/makecontext functions that
 *    unfortunately only some unices support, and is quite slow.
 *
 * -DCORO_SJLJ
 *
 *    This flavour uses SUSv2's setjmp/longjmp and sigaltstack functions to
 *    do it's job. Coroutine creation is much slower than UCONTEXT, but
 *    context switching is a bit cheaper. It should work on almost all unices.
 *
 * -DCORO_LINUX
 *
 *    CORO_SJLJ variant.
 *    Old GNU/Linux systems (<= glibc-2.1) only work with this implementation
 *    (it is very fast and therefore recommended over other methods, but
 *    doesn't work with anything newer).
 *
 * -DCORO_LOSER
 *
 *    CORO_SJLJ variant.
 *    Microsoft's highly proprietary platform doesn't support sigaltstack, and
 *    this selects a suitable workaround for this platform. It might not work
 *    with your compiler though - it has only been tested with MSVC 6.
 *
 * -DCORO_FIBER
 *
 *    Slower, but probably more portable variant for the Microsoft operating
 *    system, using fibers. Ignores the passed stack and allocates it internally.
 *    Also, due to bugs in cygwin, this does not work with cygwin.
 *
 * -DCORO_IRIX
 *
 *    CORO_SJLJ variant.
 *    For SGI's version of Microsoft's NT ;)
 *
 * -DCORO_ASM
 *
 *    Hand coded assembly, known to work only on a few architectures/ABI:
 *    GCC + arm7/x86/IA32/amd64/x86_64 + GNU/Linux and a few BSDs. Fastest
 *    choice, if it works.
 *
 * -DCORO_PTHREAD
 *
 *    Use the pthread API. You have to provide <pthread.h> and -lpthread.
 *    This is likely the slowest backend, and it also does not support fork(),
 *    so avoid it at all costs.
 *
 * If you define neither of these symbols, coro.h will try to autodetect
 * the best/safest model. To help with the autodetection, you should check
 * (e.g. using autoconf) and define the following symbols: HAVE_UCONTEXT_H
 * / HAVE_SETJMP_H / HAVE_SIGALTSTACK.
 */

/*
 * Changes when the API changes incompatibly.
 * This is ONLY the API version - there is no ABI compatibility between releases.
 *
 * Changes in API version 2:
 * replaced bogus -DCORO_LOOSE with grammatically more correct -DCORO_LOSER
 * Changes in API version 3:
 * introduced stack management (CORO_STACKALLOC)
 */
#define CORO_VERSION 3

#include <stddef.h>

/*
 * This is the type for the initialization function of a new coroutine.
 */
typedef void (*coro_func)(void *);

/*
 * A coroutine state is saved in the following structure. Treat it as an
 * opaque type. errno and sigmask might be saved, but don't rely on it,
 * implement your own switching primitive if you need that.
 */
typedef struct coro_context coro_context;

/*
 * This function creates a new coroutine. Apart from a pointer to an
 * uninitialised coro_context, it expects a pointer to the entry function
 * and the single pointer value that is given to it as argument.
 *
 * Allocating/deallocating the stack is your own responsibility.
 *
 * As a special case, if coro, arg, sptr and ssze are all zero,
 * then an "empty" coro_context will be created that is suitable
 * as an initial source for coro_transfer.
 *
 * This function is not reentrant, but putting a mutex around it
 * will work.
 */
void coro_create (coro_context *ctx, /* an uninitialised coro_context */
                  coro_func coro,    /* the coroutine code to be executed */
                  void *arg,         /* a single pointer passed to the coro */
                  void *sptr,        /* start of stack area */
                  size_t ssze);      /* size of stack area in bytes */

/*
 * The following prototype defines the coroutine switching function. It is
 * sometimes implemented as a macro, so watch out.
 *
 * This function is thread-safe and reentrant.
 */
#if 0
void coro_transfer (coro_context *prev, coro_context *next);
#endif

/*
 * The following prototype defines the coroutine destroy function. It
 * is sometimes implemented as a macro, so watch out. It also serves no
 * purpose unless you want to use the CORO_PTHREAD backend, where it is
 * used to clean up the thread. You are responsible for freeing the stack
 * and the context itself.
 *
 * This function is thread-safe and reentrant.
 */
#if 0
void coro_destroy (coro_context *ctx);
#endif

/*****************************************************************************/
/* optional stack management                                                 */
/*****************************************************************************/
/*
 * You can disable all of the stack management functions by
 * defining CORO_STACKALLOC to 0. Otherwise, they are enabled by default.
 *
 * If stack management is enabled, you can influence the implementation via these
 * symbols:
 *
 * -DCORO_USE_VALGRIND
 *
 *    If defined, then libcoro will include valgrind/valgrind.h and register
 *    and unregister stacks with valgrind.
 *
 * -DCORO_GUARDPAGES=n
 *
 *    libcoro will try to use the specified number of guard pages to protect against
 *    stack overflow. If n is 0, then the feature will be disabled. If it isn't
 *    defined, then libcoro will choose a suitable default. If guardpages are not
 *    supported on the platform, then the feature will be silently disabled.
 */
#ifndef CORO_STACKALLOC
# define CORO_STACKALLOC 1
#endif

#if CORO_STACKALLOC

/*
 * The only allowed operations on these struct members is to read the
 * "sptr" and "ssze" members to pass it to coro_create, to read the "sptr"
 * member to see if it is false, in which case the stack isn't allocated,
 * and to set the "sptr" member to 0, to indicate to coro_stack_free to
 * not actually do anything.
 */

struct coro_stack
{
  void *sptr;
  size_t ssze;
#if CORO_USE_VALGRIND
  int valgrind_id;
#endif
};

/*
 * Try to allocate a stack of at least the given size and return true if
 * successful, or false otherwise.
 *
 * The size is *NOT* specified in bytes, but in units of sizeof (void *),
 * i.e. the stack is typically 4(8) times larger on 32 bit(64 bit) platforms
 * then the size passed in.
 *
 * If size is 0, then a "suitable" stack size is chosen (usually 1-2MB).
 */
int coro_stack_alloc (struct coro_stack *stack, unsigned int size);

/*
 * Free the stack allocated by coro_stack_alloc again. It is safe to
 * call this function on the coro_stack structure even if coro_stack_alloc
 * failed.
 */
void coro_stack_free (struct coro_stack *stack);

#endif

/*
 * That was it. No other user-serviceable parts below here.
 */

/*****************************************************************************/

#if !defined CORO_LOSER      && !defined CORO_UCONTEXT \
    && !defined CORO_SJLJ    && !defined CORO_LINUX \
    && !defined CORO_IRIX    && !defined CORO_ASM \
    && !defined CORO_PTHREAD && !defined CORO_FIBER
# if defined WINDOWS && (defined __i386__ || (__x86_64__ || defined _M_IX86 || defined _M_AMD64)
#  define CORO_ASM 1
# elif defined WINDOWS || defined _WIN32
#  define CORO_LOSER 1 /* you don't win with windoze */
# elif __linux && (__i386__ || (__x86_64__ && !__ILP32__) /*|| (__arm__ && __ARM_ARCH == 7)), not working */
#  define CORO_ASM 1
# elif defined HAVE_UCONTEXT_H
#  define CORO_UCONTEXT 1
# elif defined HAVE_SETJMP_H && defined HAVE_SIGALTSTACK
#  define CORO_SJLJ 1
# else
error unknown or unsupported architecture
# endif
#endif

/*****************************************************************************/

#if CORO_UCONTEXT

# include <ucontext.h>

struct coro_context
{
  ucontext_t uc;
};

# define coro_transfer(p,n) swapcontext (&((p)->uc), &((n)->uc))
# define coro_destroy(ctx) (void *)(ctx)

#elif CORO_SJLJ || CORO_LOSER || CORO_LINUX || CORO_IRIX

# if defined(CORO_LINUX) && !defined(_GNU_SOURCE)
#  define _GNU_SOURCE /* for glibc */
# endif

/* try to disable well-meant but buggy checks in some libcs */
# ifdef _FORTIFY_SOURCE
#  undef _FORTIFY_SOURCE
#  undef __USE_FORTIFY_LEVEL /* helps some more when too much has been included already */
# endif

# if !CORO_LOSER
#  include <unistd.h>
# endif

/* solaris is hopelessly borked, it expands _XOPEN_UNIX to nothing */
# if __sun
#  undef _XOPEN_UNIX
#  define _XOPEN_UNIX 1
# endif

# include <setjmp.h>

# if _XOPEN_UNIX > 0 || defined (_setjmp)
#  define coro_jmp_buf      jmp_buf
#  define coro_setjmp(env)  _setjmp (env)
#  define coro_longjmp(env) _longjmp ((env), 1)
# elif CORO_LOSER
#  define coro_jmp_buf      jmp_buf
#  define coro_setjmp(env)  setjmp (env)
#  define coro_longjmp(env) longjmp ((env), 1)
# else
#  define coro_jmp_buf      sigjmp_buf
#  define coro_setjmp(env)  sigsetjmp (env, 0)
#  define coro_longjmp(env) siglongjmp ((env), 1)
# endif

struct coro_context
{
  coro_jmp_buf env;
};

# define coro_transfer(p,n) do { if (!coro_setjmp ((p)->env)) coro_longjmp ((n)->env); } while (0)
# define coro_destroy(ctx) (void *)(ctx)

#elif CORO_ASM

struct coro_context
{
  void **sp; /* must be at offset 0 */
};

#if __i386__ || __x86_64__
void __attribute__ ((__noinline__, __regparm__(2)))
#else
void __attribute__ ((__noinline__))
#endif
coro_transfer (coro_context *prev, coro_context *next);

# define coro_destroy(ctx) (void *)(ctx)

#elif CORO_PTHREAD

# include <pthread.h>

extern pthread_mutex_t coro_mutex;

struct coro_context
{
  pthread_cond_t cv;
  pthread_t id;
};

void coro_transfer (coro_context *prev, coro_context *next);
void coro_destroy (coro_context *ctx);

#elif CORO_FIBER

struct coro_context
{
  void *fiber;
  /* only used for initialisation */
  coro_func coro;
  void *arg;
};

void coro_transfer (coro_context *prev, coro_context *next);
void coro_destroy (coro_context *ctx);

#endif

#if __cplusplus
}
#endif

#endif

Revision:	1.58
Committed:	Sat Aug 27 12:54:52 2016 UTC (7 years, 8 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.57:	+3 -2 lines
Log Message:	* empty log message *
#	Content
1	/*
2	* Copyright (c) 2001-2012,2015 Marc Alexander Lehmann <schmorp@schmorp.de>
3	*
4	* Redistribution and use in source and binary forms, with or without modifica-
5	* tion, are permitted provided that the following conditions are met:
6	*
7	* 1. Redistributions of source code must retain the above copyright notice,
8	* this list of conditions and the following disclaimer.
9	*
10	* 2. Redistributions in binary form must reproduce the above copyright
11	* notice, this list of conditions and the following disclaimer in the
12	* documentation and/or other materials provided with the distribution.
13	*
14	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
15	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
16	* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
17	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
18	* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
20	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
21	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
22	* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
23	* OF THE POSSIBILITY OF SUCH DAMAGE.
24	*
25	* Alternatively, the contents of this file may be used under the terms of
26	* the GNU General Public License ("GPL") version 2 or any later version,
27	* in which case the provisions of the GPL are applicable instead of
28	* the above. If you wish to allow the use of your version of this file
29	* only under the terms of the GPL and not to allow others to use your
30	* version of this file under the BSD license, indicate your decision
31	* by deleting the provisions above and replace them with the notice
32	* and other provisions required by the GPL. If you do not delete the
33	* provisions above, a recipient may use your version of this file under
34	* either the BSD or the GPL.
35	*
36	* This library is modelled strictly after Ralf S. Engelschalls article at
37	* http://www.gnu.org/software/pth/rse-pmt.ps. So most of the credit must
38	* go to Ralf S. Engelschall <rse@engelschall.com>.
39	*
40	* This coroutine library is very much stripped down. You should either
41	* build your own process abstraction using it or - better - just use GNU
42	* Portable Threads, http://www.gnu.org/software/pth/.
43	*
44	*/
45
46	/*
47	* 2006-10-26 Include stddef.h on OS X to work around one of its bugs.
48	* Reported by Michael_G_Schwern.
49	* 2006-11-26 Use _setjmp instead of setjmp on GNU/Linux.
50	* 2007-04-27 Set unwind frame info if gcc 3+ and ELF is detected.
51	* Use _setjmp instead of setjmp on _XOPEN_SOURCE >= 600.
52	* 2007-05-02 Add assembly versions for x86 and amd64 (to avoid reliance
53	* on SIGUSR2 and sigaltstack in Crossfire).
54	* 2008-01-21 Disable CFI usage on anything but GNU/Linux.
55	* 2008-03-02 Switched to 2-clause BSD license with GPL exception.
56	* 2008-04-04 New (but highly unrecommended) pthreads backend.
57	* 2008-04-24 Reinstate CORO_LOSER (had wrong stack adjustments).
58	* 2008-10-30 Support assembly method on x86 with and without frame pointer.
59	* 2008-11-03 Use a global asm statement for CORO_ASM, idea by pippijn.
60	* 2008-11-05 Hopefully fix misaligned stacks with CORO_ASM/SETJMP.
61	* 2008-11-07 rbp wasn't saved in CORO_ASM on x86_64.
62	* introduce coro_destroy, which is a nop except for pthreads.
63	* speed up CORO_PTHREAD. Do no longer leak threads either.
64	* coro_create now allows one to create source coro_contexts.
65	* do not rely on makecontext passing a void * correctly.
66	* try harder to get _setjmp/_longjmp.
67	* major code cleanup/restructuring.
68	* 2008-11-10 the .cfi hacks are no longer needed.
69	* 2008-11-16 work around a freebsd pthread bug.
70	* 2008-11-19 define coro_*jmp symbols for easier porting.
71	* 2009-06-23 tentative win32-backend support for mingw32 (Yasuhiro Matsumoto).
72	* 2010-12-03 tentative support for uclibc (which lacks all sorts of things).
73	* 2011-05-30 set initial callee-saved-registers to zero with CORO_ASM.
74	* use .cfi_undefined rip on linux-amd64 for better backtraces.
75	* 2011-06-08 maybe properly implement weird windows amd64 calling conventions.
76	* 2011-07-03 rely on __GCC_HAVE_DWARF2_CFI_ASM for cfi detection.
77	* 2011-08-08 cygwin trashes stacks, use pthreads with double stack on cygwin.
78	* 2012-12-04 reduce misprediction penalty for x86/amd64 assembly switcher.
79	* 2012-12-05 experimental fiber backend (allocates stack twice).
80	* 2012-12-07 API version 3 - add coro_stack_alloc/coro_stack_free.
81	* 2012-12-21 valgrind stack registering was broken.
82	* 2015-12-05 experimental asm be for arm7, based on a patch by Nick Zavaritsky.
83	* use __name__ for predefined symbols, as in libecb.
84	* enable guard pages on arm, aarch64 and mips.
85	* 2016-08-27 try to disable _FORTIFY_SOURCE with CORO_SJLJ, as it
86	* breaks setjmp/longjmp. Also disable CORO_ASM for asm by default,
87	* as it was reported to crash.
88	*/
89
90	#ifndef CORO_H
91	#define CORO_H
92
93	#if __cplusplus
94	extern "C" {
95	#endif
96
97	/*
98	* This library consists of only three files
99	* coro.h, coro.c and LICENSE (and optionally README)
100	*
101	* It implements what is known as coroutines, in a hopefully
102	* portable way.
103	*
104	* All compiletime symbols must be defined both when including coro.h
105	* (using libcoro) as well as when compiling coro.c (the implementation).
106	*
107	* You can manually specify which flavour you want. If you don't define
108	* any of these, libcoro tries to choose a safe and fast default:
109	*
110	* -DCORO_UCONTEXT
111	*
112	* This flavour uses SUSv2's get/set/swap/makecontext functions that
113	* unfortunately only some unices support, and is quite slow.
114	*
115	* -DCORO_SJLJ
116	*
117	* This flavour uses SUSv2's setjmp/longjmp and sigaltstack functions to
118	* do it's job. Coroutine creation is much slower than UCONTEXT, but
119	* context switching is a bit cheaper. It should work on almost all unices.
120	*
121	* -DCORO_LINUX
122	*
123	* CORO_SJLJ variant.
124	* Old GNU/Linux systems (<= glibc-2.1) only work with this implementation
125	* (it is very fast and therefore recommended over other methods, but
126	* doesn't work with anything newer).
127	*
128	* -DCORO_LOSER
129	*
130	* CORO_SJLJ variant.
131	* Microsoft's highly proprietary platform doesn't support sigaltstack, and
132	* this selects a suitable workaround for this platform. It might not work
133	* with your compiler though - it has only been tested with MSVC 6.
134	*
135	* -DCORO_FIBER
136	*
137	* Slower, but probably more portable variant for the Microsoft operating
138	* system, using fibers. Ignores the passed stack and allocates it internally.
139	* Also, due to bugs in cygwin, this does not work with cygwin.
140	*
141	* -DCORO_IRIX
142	*
143	* CORO_SJLJ variant.
144	* For SGI's version of Microsoft's NT ;)
145	*
146	* -DCORO_ASM
147	*
148	* Hand coded assembly, known to work only on a few architectures/ABI:
149	* GCC + arm7/x86/IA32/amd64/x86_64 + GNU/Linux and a few BSDs. Fastest
150	* choice, if it works.
151	*
152	* -DCORO_PTHREAD
153	*
154	* Use the pthread API. You have to provide <pthread.h> and -lpthread.
155	* This is likely the slowest backend, and it also does not support fork(),
156	* so avoid it at all costs.
157	*
158	* If you define neither of these symbols, coro.h will try to autodetect
159	* the best/safest model. To help with the autodetection, you should check
160	* (e.g. using autoconf) and define the following symbols: HAVE_UCONTEXT_H
161	* / HAVE_SETJMP_H / HAVE_SIGALTSTACK.
162	*/
163
164	/*
165	* Changes when the API changes incompatibly.
166	* This is ONLY the API version - there is no ABI compatibility between releases.
167	*
168	* Changes in API version 2:
169	* replaced bogus -DCORO_LOOSE with grammatically more correct -DCORO_LOSER
170	* Changes in API version 3:
171	* introduced stack management (CORO_STACKALLOC)
172	*/
173	#define CORO_VERSION 3
174
175	#include <stddef.h>
176
177	/*
178	* This is the type for the initialization function of a new coroutine.
179	*/
180	typedef void (coro_func)(void );
181
182	/*
183	* A coroutine state is saved in the following structure. Treat it as an
184	* opaque type. errno and sigmask might be saved, but don't rely on it,
185	* implement your own switching primitive if you need that.
186	*/
187	typedef struct coro_context coro_context;
188
189	/*
190	* This function creates a new coroutine. Apart from a pointer to an
191	* uninitialised coro_context, it expects a pointer to the entry function
192	* and the single pointer value that is given to it as argument.
193	*
194	* Allocating/deallocating the stack is your own responsibility.
195	*
196	* As a special case, if coro, arg, sptr and ssze are all zero,
197	* then an "empty" coro_context will be created that is suitable
198	* as an initial source for coro_transfer.
199	*
200	* This function is not reentrant, but putting a mutex around it
201	* will work.
202	*/
203	void coro_create (coro_context ctx, / an uninitialised coro_context */
204	coro_func coro, /* the coroutine code to be executed */
205	void arg, / a single pointer passed to the coro */
206	void sptr, / start of stack area */
207	size_t ssze); /* size of stack area in bytes */
208
209	/*
210	* The following prototype defines the coroutine switching function. It is
211	* sometimes implemented as a macro, so watch out.
212	*
213	* This function is thread-safe and reentrant.
214	*/
215	#if 0
216	void coro_transfer (coro_context prev, coro_context next);
217	#endif
218
219	/*
220	* The following prototype defines the coroutine destroy function. It
221	* is sometimes implemented as a macro, so watch out. It also serves no
222	* purpose unless you want to use the CORO_PTHREAD backend, where it is
223	* used to clean up the thread. You are responsible for freeing the stack
224	* and the context itself.
225	*
226	* This function is thread-safe and reentrant.
227	*/
228	#if 0
229	void coro_destroy (coro_context *ctx);
230	#endif
231
232	/*****************************************************************************/
233	/* optional stack management */
234	/*****************************************************************************/
235	/*
236	* You can disable all of the stack management functions by
237	* defining CORO_STACKALLOC to 0. Otherwise, they are enabled by default.
238	*
239	* If stack management is enabled, you can influence the implementation via these
240	* symbols:
241	*
242	* -DCORO_USE_VALGRIND
243	*
244	* If defined, then libcoro will include valgrind/valgrind.h and register
245	* and unregister stacks with valgrind.
246	*
247	* -DCORO_GUARDPAGES=n
248	*
249	* libcoro will try to use the specified number of guard pages to protect against
250	* stack overflow. If n is 0, then the feature will be disabled. If it isn't
251	* defined, then libcoro will choose a suitable default. If guardpages are not
252	* supported on the platform, then the feature will be silently disabled.
253	*/
254	#ifndef CORO_STACKALLOC
255	# define CORO_STACKALLOC 1
256	#endif
257
258	#if CORO_STACKALLOC
259
260	/*
261	* The only allowed operations on these struct members is to read the
262	* "sptr" and "ssze" members to pass it to coro_create, to read the "sptr"
263	* member to see if it is false, in which case the stack isn't allocated,
264	* and to set the "sptr" member to 0, to indicate to coro_stack_free to
265	* not actually do anything.
266	*/
267
268	struct coro_stack
269	{
270	void *sptr;
271	size_t ssze;
272	#if CORO_USE_VALGRIND
273	int valgrind_id;
274	#endif
275	};
276
277	/*
278	* Try to allocate a stack of at least the given size and return true if
279	* successful, or false otherwise.
280	*
281	* The size is NOT specified in bytes, but in units of sizeof (void *),
282	* i.e. the stack is typically 4(8) times larger on 32 bit(64 bit) platforms
283	* then the size passed in.
284	*
285	* If size is 0, then a "suitable" stack size is chosen (usually 1-2MB).
286	*/
287	int coro_stack_alloc (struct coro_stack *stack, unsigned int size);
288
289	/*
290	* Free the stack allocated by coro_stack_alloc again. It is safe to
291	* call this function on the coro_stack structure even if coro_stack_alloc
292	* failed.
293	*/
294	void coro_stack_free (struct coro_stack *stack);
295
296	#endif
297
298	/*
299	* That was it. No other user-serviceable parts below here.
300	*/
301
302	/*****************************************************************************/
303
304	#if !defined CORO_LOSER && !defined CORO_UCONTEXT \
305	&& !defined CORO_SJLJ && !defined CORO_LINUX \
306	&& !defined CORO_IRIX && !defined CORO_ASM \
307	&& !defined CORO_PTHREAD && !defined CORO_FIBER
308	# if defined WINDOWS && (defined __i386__ \|\| (__x86_64__ \|\| defined _M_IX86 \|\| defined _M_AMD64)
309	# define CORO_ASM 1
310	# elif defined WINDOWS \|\| defined _WIN32
311	# define CORO_LOSER 1 /* you don't win with windoze */
312	# elif __linux && (__i386__ \|\| (__x86_64__ && !__ILP32__) /\|\| (__arm__ && __ARM_ARCH == 7)), not working /
313	# define CORO_ASM 1
314	# elif defined HAVE_UCONTEXT_H
315	# define CORO_UCONTEXT 1
316	# elif defined HAVE_SETJMP_H && defined HAVE_SIGALTSTACK
317	# define CORO_SJLJ 1
318	# else
319	error unknown or unsupported architecture
320	# endif
321	#endif
322
323	/*****************************************************************************/
324
325	#if CORO_UCONTEXT
326
327	# include <ucontext.h>
328
329	struct coro_context
330	{
331	ucontext_t uc;
332	};
333
334	# define coro_transfer(p,n) swapcontext (&((p)->uc), &((n)->uc))
335	# define coro_destroy(ctx) (void *)(ctx)
336
337	#elif CORO_SJLJ \|\| CORO_LOSER \|\| CORO_LINUX \|\| CORO_IRIX
338
339	# if defined(CORO_LINUX) && !defined(_GNU_SOURCE)
340	# define _GNU_SOURCE /* for glibc */
341	# endif
342
343	/* try to disable well-meant but buggy checks in some libcs */
344	# ifdef _FORTIFY_SOURCE
345	# undef _FORTIFY_SOURCE
346	# undef __USE_FORTIFY_LEVEL /* helps some more when too much has been included already */
347	# endif
348
349	# if !CORO_LOSER
350	# include <unistd.h>
351	# endif
352
353	/* solaris is hopelessly borked, it expands _XOPEN_UNIX to nothing */
354	# if __sun
355	# undef _XOPEN_UNIX
356	# define _XOPEN_UNIX 1
357	# endif
358
359	# include <setjmp.h>
360
361	# if _XOPEN_UNIX > 0 \|\| defined (_setjmp)
362	# define coro_jmp_buf jmp_buf
363	# define coro_setjmp(env) _setjmp (env)
364	# define coro_longjmp(env) _longjmp ((env), 1)
365	# elif CORO_LOSER
366	# define coro_jmp_buf jmp_buf
367	# define coro_setjmp(env) setjmp (env)
368	# define coro_longjmp(env) longjmp ((env), 1)
369	# else
370	# define coro_jmp_buf sigjmp_buf
371	# define coro_setjmp(env) sigsetjmp (env, 0)
372	# define coro_longjmp(env) siglongjmp ((env), 1)
373	# endif
374
375	struct coro_context
376	{
377	coro_jmp_buf env;
378	};
379
380	# define coro_transfer(p,n) do { if (!coro_setjmp ((p)->env)) coro_longjmp ((n)->env); } while (0)
381	# define coro_destroy(ctx) (void *)(ctx)
382
383	#elif CORO_ASM
384
385	struct coro_context
386	{
387	void *sp; / must be at offset 0 */
388	};
389
390	#if __i386__ \|\| __x86_64__
391	void __attribute__ ((__noinline__, __regparm__(2)))
392	#else
393	void __attribute__ ((__noinline__))
394	#endif
395	coro_transfer (coro_context prev, coro_context next);
396
397	# define coro_destroy(ctx) (void *)(ctx)
398
399	#elif CORO_PTHREAD
400
401	# include <pthread.h>
402
403	extern pthread_mutex_t coro_mutex;
404
405	struct coro_context
406	{
407	pthread_cond_t cv;
408	pthread_t id;
409	};
410
411	void coro_transfer (coro_context prev, coro_context next);
412	void coro_destroy (coro_context *ctx);
413
414	#elif CORO_FIBER
415
416	struct coro_context
417	{
418	void *fiber;
419	/* only used for initialisation */
420	coro_func coro;
421	void *arg;
422	};
423
424	void coro_transfer (coro_context prev, coro_context next);
425	void coro_destroy (coro_context *ctx);
426
427	#endif
428
429	#if __cplusplus
430	}
431	#endif
432
433	#endif
434