2009-03-26 Jonathan Chambers <joncham@gmail.com>

[mono-project.git] / libgc / include / gc.h

/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
 * Copyright 1996-1999 by Silicon Graphics.  All rights reserved.
 * Copyright 1999 by Hewlett-Packard Company.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

/*
 * Note that this defines a large number of tuning hooks, which can
 * safely be ignored in nearly all cases.  For normal use it suffices
 * to call only GC_MALLOC and perhaps GC_REALLOC.
 * For better performance, also look at GC_MALLOC_ATOMIC, and
 * GC_enable_incremental.  If you need an action to be performed
 * immediately before an object is collected, look at GC_register_finalizer.
 * If you are using Solaris threads, look at the end of this file.
 * Everything else is best ignored unless you encounter performance
 * problems.
 */
 
#ifndef _GC_H

# define _GC_H

# include "gc_config_macros.h"

# if defined(__STDC__) || defined(__cplusplus) || defined(_AIX)
#   define GC_PROTO(args) args
    typedef void * GC_PTR;
#   define GC_CONST const
# else
#   define GC_PROTO(args) ()
    typedef char * GC_PTR;
#   define GC_CONST
#  endif

# ifdef __cplusplus
    extern "C" {
# endif


/* Define word and signed_word to be unsigned and signed types of the   */
/* size as char * or void *.  There seems to be no way to do this       */
/* even semi-portably.  The following is probably no better/worse       */
/* than almost anything else.                                           */
/* The ANSI standard suggests that size_t and ptr_diff_t might be       */
/* better choices.  But those had incorrect definitions on some older   */
/* systems.  Notably "typedef int size_t" is WRONG.                     */
#ifndef _WIN64
  typedef unsigned long GC_word;
  typedef long GC_signed_word;
#else
  /* Win64 isn't really supported yet, but this is the first step. And  */
  /* it might cause error messages to show up in more plausible places. */
  /* This needs basetsd.h, which is included by windows.h.              */
  typedef unsigned __int64 GC_word;
  typedef __int64 GC_signed_word;
#endif

/* Public read-only variables */

GC_API GC_word GC_gc_no;/* Counter incremented per collection.          */
                        /* Includes empty GCs at startup.               */

GC_API int GC_parallel; /* GC is parallelized for performance on        */
                        /* multiprocessors.  Currently set only         */
                        /* implicitly if collector is built with        */
                        /* -DPARALLEL_MARK and if either:               */
                        /*  Env variable GC_NPROC is set to > 1, or     */
                        /*  GC_NPROC is not set and this is an MP.      */
                        /* If GC_parallel is set, incremental           */
                        /* collection is only partially functional,     */
                        /* and may not be desirable.                    */
                        

/* Public R/W variables */

GC_API GC_PTR (*GC_oom_fn) GC_PROTO((size_t bytes_requested));
                        /* When there is insufficient memory to satisfy */
                        /* an allocation request, we return             */
                        /* (*GC_oom_fn)().  By default this just        */
                        /* returns 0.                                   */
                        /* If it returns, it must return 0 or a valid   */
                        /* pointer to a previously allocated heap       */
                        /* object.                                      */

typedef enum {
        GC_EVENT_START,
        GC_EVENT_MARK_START,
        GC_EVENT_MARK_END,
        GC_EVENT_RECLAIM_START,
        GC_EVENT_RECLAIM_END,
        GC_EVENT_END,
        GC_EVENT_PRE_STOP_WORLD,
        GC_EVENT_POST_STOP_WORLD,
        GC_EVENT_PRE_START_WORLD,
        GC_EVENT_POST_START_WORLD
} GCEventType;

GC_API void (*GC_notify_event) GC_PROTO((GCEventType event_type));
                        /* Invoked at specific points during every collection.
                         */
                         
GC_API void (*GC_on_heap_resize) GC_PROTO((size_t new_size));
                        /* Invoked when the heap grows or shrinks        */

GC_API int GC_find_leak;
                        /* Do not actually garbage collect, but simply  */
                        /* report inaccessible memory that was not      */
                        /* deallocated with GC_free.  Initial value     */
                        /* is determined by FIND_LEAK macro.            */

GC_API int GC_all_interior_pointers;
                        /* Arrange for pointers to object interiors to  */
                        /* be recognized as valid.  May not be changed  */
                        /* after GC initialization.                     */
                        /* Initial value is determined by               */
                        /* -DALL_INTERIOR_POINTERS.                     */
                        /* Unless DONT_ADD_BYTE_AT_END is defined, this */
                        /* also affects whether sizes are increased by  */
                        /* at least a byte to allow "off the end"       */
                        /* pointer recognition.                         */
                        /* MUST BE 0 or 1.                              */

GC_API int GC_quiet;    /* Disable statistics output.  Only matters if  */
                        /* collector has been compiled with statistics  */
                        /* enabled.  This involves a performance cost,  */
                        /* and is thus not the default.                 */

GC_API int GC_finalize_on_demand;
                        /* If nonzero, finalizers will only be run in   */
                        /* response to an explicit GC_invoke_finalizers */
                        /* call.  The default is determined by whether  */
                        /* the FINALIZE_ON_DEMAND macro is defined      */
                        /* when the collector is built.                 */

GC_API int GC_java_finalization;
                        /* Mark objects reachable from finalizable      */
                        /* objects in a separate postpass.  This makes  */
                        /* it a bit safer to use non-topologically-     */
                        /* ordered finalization.  Default value is      */
                        /* determined by JAVA_FINALIZATION macro.       */

GC_API void (* GC_finalizer_notifier)(void);
                        /* Invoked by the collector when there are      */
                        /* objects to be finalized.  Invoked at most    */
                        /* once per GC cycle.  Never invoked unless     */
                        /* GC_finalize_on_demand is set.                */
                        /* Typically this will notify a finalization    */
                        /* thread, which will call GC_invoke_finalizers */
                        /* in response.                                 */

GC_API int GC_dont_gc;  /* != 0 ==> Dont collect.  In versions 6.2a1+,  */
                        /* this overrides explicit GC_gcollect() calls. */
                        /* Used as a counter, so that nested enabling   */
                        /* and disabling work correctly.  Should        */
                        /* normally be updated with GC_enable() and     */
                        /* GC_disable() calls.                          */
                        /* Direct assignment to GC_dont_gc is           */
                        /* deprecated.                                  */

GC_API int GC_dont_expand;
                        /* Dont expand heap unless explicitly requested */
                        /* or forced to.                                */

GC_API int GC_use_entire_heap;
                /* Causes the nonincremental collector to use the       */
                /* entire heap before collecting.  This was the only    */
                /* option for GC versions < 5.0.  This sometimes        */
                /* results in more large block fragmentation, since     */
                /* very larg blocks will tend to get broken up          */
                /* during each GC cycle.  It is likely to result in a   */
                /* larger working set, but lower collection             */
                /* frequencies, and hence fewer instructions executed   */
                /* in the collector.                                    */

GC_API int GC_full_freq;    /* Number of partial collections between    */
                            /* full collections.  Matters only if       */
                            /* GC_incremental is set.                   */
                            /* Full collections are also triggered if   */
                            /* the collector detects a substantial      */
                            /* increase in the number of in-use heap    */
                            /* blocks.  Values in the tens are now      */
                            /* perfectly reasonable, unlike for         */
                            /* earlier GC versions.                     */
                        
GC_API GC_word GC_non_gc_bytes;
                        /* Bytes not considered candidates for collection. */
                        /* Used only to control scheduling of collections. */
                        /* Updated by GC_malloc_uncollectable and GC_free. */
                        /* Wizards only.                                   */

GC_API int GC_no_dls;
                        /* Don't register dynamic library data segments. */
                        /* Wizards only.  Should be used only if the     */
                        /* application explicitly registers all roots.   */
                        /* In Microsoft Windows environments, this will  */
                        /* usually also prevent registration of the      */
                        /* main data segment as part of the root set.    */

GC_API GC_word GC_free_space_divisor;
                        /* We try to make sure that we allocate at      */
                        /* least N/GC_free_space_divisor bytes between  */
                        /* collections, where N is the heap size plus   */
                        /* a rough estimate of the root set size.       */
                        /* Initially, GC_free_space_divisor = 3.        */
                        /* Increasing its value will use less space     */
                        /* but more collection time.  Decreasing it     */
                        /* will appreciably decrease collection time    */
                        /* at the expense of space.                     */
                        /* GC_free_space_divisor = 1 will effectively   */
                        /* disable collections.                         */

GC_API GC_word GC_max_retries;
                        /* The maximum number of GCs attempted before   */
                        /* reporting out of memory after heap           */
                        /* expansion fails.  Initially 0.               */
                        

GC_API char *GC_stackbottom;    /* Cool end of user stack.              */
                                /* May be set in the client prior to    */
                                /* calling any GC_ routines.  This      */
                                /* avoids some overhead, and            */
                                /* potentially some signals that can    */
                                /* confuse debuggers.  Otherwise the    */
                                /* collector attempts to set it         */
                                /* automatically.                       */
                                /* For multithreaded code, this is the  */
                                /* cold end of the stack for the        */
                                /* primordial thread.                   */      
                                
GC_API int GC_dont_precollect;  /* Don't collect as part of             */
                                /* initialization.  Should be set only  */
                                /* if the client wants a chance to      */
                                /* manually initialize the root set     */
                                /* before the first collection.         */
                                /* Interferes with blacklisting.        */
                                /* Wizards only.                        */

GC_API unsigned long GC_time_limit;
                                /* If incremental collection is enabled, */
                                /* We try to terminate collections       */
                                /* after this many milliseconds.  Not a  */
                                /* hard time bound.  Setting this to     */
                                /* GC_TIME_UNLIMITED will essentially    */
                                /* disable incremental collection while  */
                                /* leaving generational collection       */
                                /* enabled.                              */
#       define GC_TIME_UNLIMITED 999999
                                /* Setting GC_time_limit to this value   */
                                /* will disable the "pause time exceeded"*/
                                /* tests.                                */

/* Public procedures */

/* Initialize the collector.  This is only required when using thread-local
 * allocation, since unlike the regular allocation routines, GC_local_malloc
 * is not self-initializing.  If you use GC_local_malloc you should arrange
 * to call this somehow (e.g. from a constructor) before doing any allocation.
 * For win32 threads, it needs to be called explicitly.
 */
GC_API void GC_init GC_PROTO((void));

/*
 * general purpose allocation routines, with roughly malloc calling conv.
 * The atomic versions promise that no relevant pointers are contained
 * in the object.  The nonatomic versions guarantee that the new object
 * is cleared.  GC_malloc_stubborn promises that no changes to the object
 * will occur after GC_end_stubborn_change has been called on the
 * result of GC_malloc_stubborn. GC_malloc_uncollectable allocates an object
 * that is scanned for pointers to collectable objects, but is not itself
 * collectable.  The object is scanned even if it does not appear to
 * be reachable.  GC_malloc_uncollectable and GC_free called on the resulting
 * object implicitly update GC_non_gc_bytes appropriately.
 *
 * Note that the GC_malloc_stubborn support is stubbed out by default
 * starting in 6.0.  GC_malloc_stubborn is an alias for GC_malloc unless
 * the collector is built with STUBBORN_ALLOC defined.
 */
GC_API GC_PTR GC_malloc GC_PROTO((size_t size_in_bytes));
GC_API GC_PTR GC_malloc_atomic GC_PROTO((size_t size_in_bytes));
GC_API GC_PTR GC_malloc_uncollectable GC_PROTO((size_t size_in_bytes));
GC_API GC_PTR GC_malloc_stubborn GC_PROTO((size_t size_in_bytes));

/* The following is only defined if the library has been suitably       */
/* compiled:                                                            */
GC_API GC_PTR GC_malloc_atomic_uncollectable GC_PROTO((size_t size_in_bytes));

/* Explicitly deallocate an object.  Dangerous if used incorrectly.     */
/* Requires a pointer to the base of an object.                         */
/* If the argument is stubborn, it should not be changeable when freed. */
/* An object should not be enable for finalization when it is           */
/* explicitly deallocated.                                              */
/* GC_free(0) is a no-op, as required by ANSI C for free.               */
GC_API void GC_free GC_PROTO((GC_PTR object_addr));

/*
 * Stubborn objects may be changed only if the collector is explicitly informed.
 * The collector is implicitly informed of coming change when such
 * an object is first allocated.  The following routines inform the
 * collector that an object will no longer be changed, or that it will
 * once again be changed.  Only nonNIL pointer stores into the object
 * are considered to be changes.  The argument to GC_end_stubborn_change
 * must be exacly the value returned by GC_malloc_stubborn or passed to
 * GC_change_stubborn.  (In the second case it may be an interior pointer
 * within 512 bytes of the beginning of the objects.)
 * There is a performance penalty for allowing more than
 * one stubborn object to be changed at once, but it is acceptable to
 * do so.  The same applies to dropping stubborn objects that are still
 * changeable.
 */
GC_API void GC_change_stubborn GC_PROTO((GC_PTR));
GC_API void GC_end_stubborn_change GC_PROTO((GC_PTR));

/* Return a pointer to the base (lowest address) of an object given     */
/* a pointer to a location within the object.                           */
/* I.e. map an interior pointer to the corresponding bas pointer.       */
/* Note that with debugging allocation, this returns a pointer to the   */
/* actual base of the object, i.e. the debug information, not to        */
/* the base of the user object.                                         */
/* Return 0 if displaced_pointer doesn't point to within a valid        */
/* object.                                                              */
/* Note that a deallocated object in the garbage collected heap         */
/* may be considered valid, even if it has been deallocated with        */
/* GC_free.                                                             */
GC_API GC_PTR GC_base GC_PROTO((GC_PTR displaced_pointer));

/* Given a pointer to the base of an object, return its size in bytes.  */
/* The returned size may be slightly larger than what was originally    */
/* requested.                                                           */
GC_API size_t GC_size GC_PROTO((GC_PTR object_addr));

/* For compatibility with C library.  This is occasionally faster than  */
/* a malloc followed by a bcopy.  But if you rely on that, either here  */
/* or with the standard C library, your code is broken.  In my          */
/* opinion, it shouldn't have been invented, but now we're stuck. -HB   */
/* The resulting object has the same kind as the original.              */
/* If the argument is stubborn, the result will have changes enabled.   */
/* It is an error to have changes enabled for the original object.      */
/* Follows ANSI comventions for NULL old_object.                        */
GC_API GC_PTR GC_realloc
        GC_PROTO((GC_PTR old_object, size_t new_size_in_bytes));
                                   
/* Explicitly increase the heap size.   */
/* Returns 0 on failure, 1 on success.  */
GC_API int GC_expand_hp GC_PROTO((size_t number_of_bytes));

/* Limit the heap size to n bytes.  Useful when you're debugging,       */
/* especially on systems that don't handle running out of memory well.  */
/* n == 0 ==> unbounded.  This is the default.                          */
GC_API void GC_set_max_heap_size GC_PROTO((GC_word n));

/* Inform the collector that a certain section of statically allocated  */
/* memory contains no pointers to garbage collected memory.  Thus it    */
/* need not be scanned.  This is sometimes important if the application */
/* maps large read/write files into the address space, which could be   */
/* mistaken for dynamic library data segments on some systems.          */
GC_API void GC_exclude_static_roots GC_PROTO((GC_PTR start, GC_PTR finish));

/* Clear the set of root segments.  Wizards only. */
GC_API void GC_clear_roots GC_PROTO((void));

/* Add a root segment.  Wizards only. */
GC_API void GC_add_roots GC_PROTO((char * low_address,
                                   char * high_address_plus_1));

/* Remove a root segment.  Wizards only. */
GC_API void GC_remove_roots GC_PROTO((char * low_address, 
    char * high_address_plus_1));

/* Add a displacement to the set of those considered valid by the       */
/* collector.  GC_register_displacement(n) means that if p was returned */
/* by GC_malloc, then (char *)p + n will be considered to be a valid    */
/* pointer to p.  N must be small and less than the size of p.          */
/* (All pointers to the interior of objects from the stack are          */
/* considered valid in any case.  This applies to heap objects and      */
/* static data.)                                                        */
/* Preferably, this should be called before any other GC procedures.    */
/* Calling it later adds to the probability of excess memory            */
/* retention.                                                           */
/* This is a no-op if the collector has recognition of                  */
/* arbitrary interior pointers enabled, which is now the default.       */
GC_API void GC_register_displacement GC_PROTO((GC_word n));

/* The following version should be used if any debugging allocation is  */
/* being done.                                                          */
GC_API void GC_debug_register_displacement GC_PROTO((GC_word n));

/* Explicitly trigger a full, world-stop collection.    */
GC_API void GC_gcollect GC_PROTO((void));

/* Trigger a full world-stopped collection.  Abort the collection if    */
/* and when stop_func returns a nonzero value.  Stop_func will be       */
/* called frequently, and should be reasonably fast.  This works even   */
/* if virtual dirty bits, and hence incremental collection is not       */
/* available for this architecture.  Collections can be aborted faster  */
/* than normal pause times for incremental collection.  However,        */
/* aborted collections do no useful work; the next collection needs     */
/* to start from the beginning.                                         */
/* Return 0 if the collection was aborted, 1 if it succeeded.           */
typedef int (* GC_stop_func) GC_PROTO((void));
GC_API int GC_try_to_collect GC_PROTO((GC_stop_func stop_func));

/* Return the number of bytes in the heap.  Excludes collector private  */
/* data structures.  Includes empty blocks and fragmentation loss.      */
/* Includes some pages that were allocated but never written.           */
GC_API size_t GC_get_heap_size GC_PROTO((void));

/* Return a lower bound on the number of free bytes in the heap.        */
GC_API size_t GC_get_free_bytes GC_PROTO((void));

/* Return the number of bytes allocated since the last collection.      */
GC_API size_t GC_get_bytes_since_gc GC_PROTO((void));

/* Return the total number of bytes allocated in this process.          */
/* Never decreases, except due to wrapping.                             */
GC_API size_t GC_get_total_bytes GC_PROTO((void));

/* Disable garbage collection.  Even GC_gcollect calls will be          */
/* ineffective.                                                         */
GC_API void GC_disable GC_PROTO((void));

/* Reenable garbage collection.  GC_disable() and GC_enable() calls     */
/* nest.  Garbage collection is enabled if the number of calls to both  */
/* both functions is equal.                                             */
GC_API void GC_enable GC_PROTO((void));

/* Enable incremental/generational collection.  */
/* Not advisable unless dirty bits are          */
/* available or most heap objects are           */
/* pointerfree(atomic) or immutable.            */
/* Don't use in leak finding mode.              */
/* Ignored if GC_dont_gc is true.               */
/* Only the generational piece of this is       */
/* functional if GC_parallel is TRUE            */
/* or if GC_time_limit is GC_TIME_UNLIMITED.    */
/* Causes GC_local_gcj_malloc() to revert to    */
/* locked allocation.  Must be called           */
/* before any GC_local_gcj_malloc() calls.      */
GC_API void GC_enable_incremental GC_PROTO((void));

/* Does incremental mode write-protect pages?  Returns zero or  */
/* more of the following, or'ed together:                       */
#define GC_PROTECTS_POINTER_HEAP  1 /* May protect non-atomic objs.     */
#define GC_PROTECTS_PTRFREE_HEAP  2
#define GC_PROTECTS_STATIC_DATA   4 /* Curently never.                  */
#define GC_PROTECTS_STACK         8 /* Probably impractical.            */

#define GC_PROTECTS_NONE 0
GC_API int GC_incremental_protection_needs GC_PROTO((void));

/* Perform some garbage collection work, if appropriate.        */
/* Return 0 if there is no more work to be done.                */
/* Typically performs an amount of work corresponding roughly   */
/* to marking from one page.  May do more work if further       */
/* progress requires it, e.g. if incremental collection is      */
/* disabled.  It is reasonable to call this in a wait loop      */
/* until it returns 0.                                          */
GC_API int GC_collect_a_little GC_PROTO((void));

/* Allocate an object of size lb bytes.  The client guarantees that     */
/* as long as the object is live, it will be referenced by a pointer    */
/* that points to somewhere within the first 256 bytes of the object.   */
/* (This should normally be declared volatile to prevent the compiler   */
/* from invalidating this assertion.)  This routine is only useful      */
/* if a large array is being allocated.  It reduces the chance of       */
/* accidentally retaining such an array as a result of scanning an      */
/* integer that happens to be an address inside the array.  (Actually,  */
/* it reduces the chance of the allocator not finding space for such    */
/* an array, since it will try hard to avoid introducing such a false   */
/* reference.)  On a SunOS 4.X or MS Windows system this is recommended */
/* for arrays likely to be larger than 100K or so.  For other systems,  */
/* or if the collector is not configured to recognize all interior      */
/* pointers, the threshold is normally much higher.                     */
GC_API GC_PTR GC_malloc_ignore_off_page GC_PROTO((size_t lb));
GC_API GC_PTR GC_malloc_atomic_ignore_off_page GC_PROTO((size_t lb));

#if defined(__sgi) && !defined(__GNUC__) && _COMPILER_VERSION >= 720
#   define GC_ADD_CALLER
#   define GC_RETURN_ADDR (GC_word)__return_address
#endif

#ifdef __linux__
# include <features.h>
# if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1 || __GLIBC__ > 2) \
     && !defined(__ia64__)
#   ifndef GC_HAVE_BUILTIN_BACKTRACE
#     define GC_HAVE_BUILTIN_BACKTRACE
#   endif
# endif
# if defined(__i386__) || defined(__x86_64__)
#   define GC_CAN_SAVE_CALL_STACKS
# endif
#endif

#if defined(GC_HAVE_BUILTIN_BACKTRACE) && !defined(GC_CAN_SAVE_CALL_STACKS)
# define GC_CAN_SAVE_CALL_STACKS
#endif

#if defined(__sparc__)
#   define GC_CAN_SAVE_CALL_STACKS
#endif

/* If we're on an a platform on which we can't save call stacks, but    */
/* gcc is normally used, we go ahead and define GC_ADD_CALLER.          */
/* We make this decision independent of whether gcc is actually being   */
/* used, in order to keep the interface consistent, and allow mixing    */
/* of compilers.                                                        */
/* This may also be desirable if it is possible but expensive to        */
/* retrieve the call chain.                                             */
#if (defined(__linux__) || defined(__NetBSD__) || defined(__OpenBSD__) \
     || defined(__FreeBSD__)) & !defined(GC_CAN_SAVE_CALL_STACKS)
# define GC_ADD_CALLER
# if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95) 
    /* gcc knows how to retrieve return address, but we don't know */
    /* how to generate call stacks.                                */
#   define GC_RETURN_ADDR (GC_word)__builtin_return_address(0)
# else
    /* Just pass 0 for gcc compatibility. */
#   define GC_RETURN_ADDR 0
# endif
#endif

#ifdef GC_ADD_CALLER
#  define GC_EXTRAS GC_RETURN_ADDR, __FILE__, __LINE__
#  define GC_EXTRA_PARAMS GC_word ra, GC_CONST char * s, int i
#else
#  define GC_EXTRAS __FILE__, __LINE__
#  define GC_EXTRA_PARAMS GC_CONST char * s, int i
#endif

/* Debugging (annotated) allocation.  GC_gcollect will check            */
/* objects allocated in this way for overwrites, etc.                   */
GC_API GC_PTR GC_debug_malloc
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API GC_PTR GC_debug_malloc_atomic
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API GC_PTR GC_debug_malloc_uncollectable
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API GC_PTR GC_debug_malloc_stubborn
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API GC_PTR GC_debug_malloc_ignore_off_page
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API GC_PTR GC_debug_malloc_atomic_ignore_off_page
        GC_PROTO((size_t size_in_bytes, GC_EXTRA_PARAMS));
GC_API void GC_debug_free GC_PROTO((GC_PTR object_addr));
GC_API GC_PTR GC_debug_realloc
        GC_PROTO((GC_PTR old_object, size_t new_size_in_bytes,
                  GC_EXTRA_PARAMS));
GC_API void GC_debug_change_stubborn GC_PROTO((GC_PTR));
GC_API void GC_debug_end_stubborn_change GC_PROTO((GC_PTR));

/* Routines that allocate objects with debug information (like the      */
/* above), but just fill in dummy file and line number information.     */
/* Thus they can serve as drop-in malloc/realloc replacements.  This    */
/* can be useful for two reasons:                                       */
/* 1) It allows the collector to be built with DBG_HDRS_ALL defined     */
/*    even if some allocation calls come from 3rd party libraries       */
/*    that can't be recompiled.                                         */
/* 2) On some platforms, the file and line information is redundant,    */
/*    since it can be reconstructed from a stack trace.  On such        */
/*    platforms it may be more convenient not to recompile, e.g. for    */
/*    leak detection.  This can be accomplished by instructing the      */
/*    linker to replace malloc/realloc with these.                      */
GC_API GC_PTR GC_debug_malloc_replacement GC_PROTO((size_t size_in_bytes));
GC_API GC_PTR GC_debug_realloc_replacement
              GC_PROTO((GC_PTR object_addr, size_t size_in_bytes));
                                 
# ifdef GC_DEBUG
#   define GC_MALLOC(sz) GC_debug_malloc(sz, GC_EXTRAS)
#   define GC_MALLOC_ATOMIC(sz) GC_debug_malloc_atomic(sz, GC_EXTRAS)
#   define GC_MALLOC_UNCOLLECTABLE(sz) \
                        GC_debug_malloc_uncollectable(sz, GC_EXTRAS)
#   define GC_MALLOC_IGNORE_OFF_PAGE(sz) \
                        GC_debug_malloc_ignore_off_page(sz, GC_EXTRAS)
#   define GC_MALLOC_ATOMIC_IGNORE_OFF_PAGE(sz) \
                        GC_debug_malloc_atomic_ignore_off_page(sz, GC_EXTRAS)
#   define GC_REALLOC(old, sz) GC_debug_realloc(old, sz, GC_EXTRAS)
#   define GC_FREE(p) GC_debug_free(p)
#   define GC_REGISTER_FINALIZER(p, f, d, of, od) \
        GC_debug_register_finalizer(p, f, d, of, od)
#   define GC_REGISTER_FINALIZER_IGNORE_SELF(p, f, d, of, od) \
        GC_debug_register_finalizer_ignore_self(p, f, d, of, od)
#   define GC_REGISTER_FINALIZER_NO_ORDER(p, f, d, of, od) \
        GC_debug_register_finalizer_no_order(p, f, d, of, od)
#   define GC_MALLOC_STUBBORN(sz) GC_debug_malloc_stubborn(sz, GC_EXTRAS);
#   define GC_CHANGE_STUBBORN(p) GC_debug_change_stubborn(p)
#   define GC_END_STUBBORN_CHANGE(p) GC_debug_end_stubborn_change(p)
#   define GC_GENERAL_REGISTER_DISAPPEARING_LINK(link, obj) \
        GC_general_register_disappearing_link(link, GC_base(obj))
#   define GC_REGISTER_DISPLACEMENT(n) GC_debug_register_displacement(n)
# else
#   define GC_MALLOC(sz) GC_malloc(sz)
#   define GC_MALLOC_ATOMIC(sz) GC_malloc_atomic(sz)
#   define GC_MALLOC_UNCOLLECTABLE(sz) GC_malloc_uncollectable(sz)
#   define GC_MALLOC_IGNORE_OFF_PAGE(sz) \
                        GC_malloc_ignore_off_page(sz)
#   define GC_MALLOC_ATOMIC_IGNORE_OFF_PAGE(sz) \
                        GC_malloc_atomic_ignore_off_page(sz)
#   define GC_REALLOC(old, sz) GC_realloc(old, sz)
#   define GC_FREE(p) GC_free(p)
#   define GC_REGISTER_FINALIZER(p, f, d, of, od) \
        GC_register_finalizer(p, f, d, of, od)
#   define GC_REGISTER_FINALIZER_IGNORE_SELF(p, f, d, of, od) \
        GC_register_finalizer_ignore_self(p, f, d, of, od)
#   define GC_REGISTER_FINALIZER_NO_ORDER(p, f, d, of, od) \
        GC_register_finalizer_no_order(p, f, d, of, od)
#   define GC_MALLOC_STUBBORN(sz) GC_malloc_stubborn(sz)
#   define GC_CHANGE_STUBBORN(p) GC_change_stubborn(p)
#   define GC_END_STUBBORN_CHANGE(p) GC_end_stubborn_change(p)
#   define GC_GENERAL_REGISTER_DISAPPEARING_LINK(link, obj) \
        GC_general_register_disappearing_link(link, obj)
#   define GC_REGISTER_DISPLACEMENT(n) GC_register_displacement(n)
# endif
/* The following are included because they are often convenient, and    */
/* reduce the chance for a misspecifed size argument.  But calls may    */
/* expand to something syntactically incorrect if t is a complicated    */
/* type expression.                                                     */
# define GC_NEW(t) (t *)GC_MALLOC(sizeof (t))
# define GC_NEW_ATOMIC(t) (t *)GC_MALLOC_ATOMIC(sizeof (t))
# define GC_NEW_STUBBORN(t) (t *)GC_MALLOC_STUBBORN(sizeof (t))
# define GC_NEW_UNCOLLECTABLE(t) (t *)GC_MALLOC_UNCOLLECTABLE(sizeof (t))

/* Finalization.  Some of these primitives are grossly unsafe.          */
/* The idea is to make them both cheap, and sufficient to build         */
/* a safer layer, closer to Modula-3, Java, or PCedar finalization.     */
/* The interface represents my conclusions from a long discussion       */
/* with Alan Demers, Dan Greene, Carl Hauser, Barry Hayes,              */
/* Christian Jacobi, and Russ Atkinson.  It's not perfect, and          */
/* probably nobody else agrees with it.     Hans-J. Boehm  3/13/92      */
typedef void (*GC_finalization_proc)
        GC_PROTO((GC_PTR obj, GC_PTR client_data));

GC_API void GC_register_finalizer
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));
GC_API void GC_debug_register_finalizer
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));
        /* When obj is no longer accessible, invoke             */
        /* (*fn)(obj, cd).  If a and b are inaccessible, and    */
        /* a points to b (after disappearing links have been    */
        /* made to disappear), then only a will be              */
        /* finalized.  (If this does not create any new         */
        /* pointers to b, then b will be finalized after the    */
        /* next collection.)  Any finalizable object that       */
        /* is reachable from itself by following one or more    */
        /* pointers will not be finalized (or collected).       */
        /* Thus cycles involving finalizable objects should     */
        /* be avoided, or broken by disappearing links.         */
        /* All but the last finalizer registered for an object  */
        /* is ignored.                                          */
        /* Finalization may be removed by passing 0 as fn.      */
        /* Finalizers are implicitly unregistered just before   */
        /* they are invoked.                                    */
        /* The old finalizer and client data are stored in      */
        /* *ofn and *ocd.                                       */ 
        /* Fn is never invoked on an accessible object,         */
        /* provided hidden pointers are converted to real       */
        /* pointers only if the allocation lock is held, and    */
        /* such conversions are not performed by finalization   */
        /* routines.                                            */
        /* If GC_register_finalizer is aborted as a result of   */
        /* a signal, the object may be left with no             */
        /* finalization, even if neither the old nor new        */
        /* finalizer were NULL.                                 */
        /* Obj should be the nonNULL starting address of an     */
        /* object allocated by GC_malloc or friends.            */
        /* Note that any garbage collectable object referenced  */
        /* by cd will be considered accessible until the        */
        /* finalizer is invoked.                                */

/* Another versions of the above follow.  It ignores            */
/* self-cycles, i.e. pointers from a finalizable object to      */
/* itself.  There is a stylistic argument that this is wrong,   */
/* but it's unavoidable for C++, since the compiler may         */
/* silently introduce these.  It's also benign in that specific */
/* case.  And it helps if finalizable objects are split to      */
/* avoid cycles.                                                */
/* Note that cd will still be viewed as accessible, even if it  */
/* refers to the object itself.                                 */
GC_API void GC_register_finalizer_ignore_self
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));
GC_API void GC_debug_register_finalizer_ignore_self
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));

/* Another version of the above.  It ignores all cycles.        */
/* It should probably only be used by Java implementations.     */
/* Note that cd will still be viewed as accessible, even if it  */
/* refers to the object itself.                                 */
GC_API void GC_register_finalizer_no_order
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));
GC_API void GC_debug_register_finalizer_no_order
        GC_PROTO((GC_PTR obj, GC_finalization_proc fn, GC_PTR cd,
                  GC_finalization_proc *ofn, GC_PTR *ocd));


/* The following routine may be used to break cycles between    */
/* finalizable objects, thus causing cyclic finalizable         */
/* objects to be finalized in the correct order.  Standard      */
/* use involves calling GC_register_disappearing_link(&p),      */
/* where p is a pointer that is not followed by finalization    */
/* code, and should not be considered in determining            */
/* finalization order.                                          */
GC_API int GC_register_disappearing_link GC_PROTO((GC_PTR * /* link */));
        /* Link should point to a field of a heap allocated     */
        /* object obj.  *link will be cleared when obj is       */
        /* found to be inaccessible.  This happens BEFORE any   */
        /* finalization code is invoked, and BEFORE any         */
        /* decisions about finalization order are made.         */
        /* This is useful in telling the finalizer that         */
        /* some pointers are not essential for proper           */
        /* finalization.  This may avoid finalization cycles.   */
        /* Note that obj may be resurrected by another          */
        /* finalizer, and thus the clearing of *link may        */
        /* be visible to non-finalization code.                 */
        /* There's an argument that an arbitrary action should  */
        /* be allowed here, instead of just clearing a pointer. */
        /* But this causes problems if that action alters, or   */
        /* examines connectivity.                               */
        /* Returns 1 if link was already registered, 0          */
        /* otherwise.                                           */
        /* Only exists for backward compatibility.  See below:  */
        
GC_API int GC_general_register_disappearing_link
        GC_PROTO((GC_PTR * /* link */, GC_PTR obj));
        /* A slight generalization of the above. *link is       */
        /* cleared when obj first becomes inaccessible.  This   */
        /* can be used to implement weak pointers easily and    */
        /* safely. Typically link will point to a location      */
        /* holding a disguised pointer to obj.  (A pointer      */
        /* inside an "atomic" object is effectively             */
        /* disguised.)   In this way soft                       */
        /* pointers are broken before any object                */
        /* reachable from them are finalized.  Each link        */
        /* May be registered only once, i.e. with one obj       */
        /* value.  This was added after a long email discussion */
        /* with John Ellis.                                     */
        /* Obj must be a pointer to the first word of an object */
        /* we allocated.  It is unsafe to explicitly deallocate */
        /* the object containing link.  Explicitly deallocating */
        /* obj may or may not cause link to eventually be       */
        /* cleared.                                             */
GC_API int GC_unregister_disappearing_link GC_PROTO((GC_PTR * /* link */));
        /* Returns 0 if link was not actually registered.       */
        /* Undoes a registration by either of the above two     */
        /* routines.                                            */

/* Returns !=0  if GC_invoke_finalizers has something to do.            */
GC_API int GC_should_invoke_finalizers GC_PROTO((void));

GC_API int GC_invoke_finalizers GC_PROTO((void));
        /* Run finalizers for all objects that are ready to     */
        /* be finalized.  Return the number of finalizers       */
        /* that were run.  Normally this is also called         */
        /* implicitly during some allocations.  If              */
        /* GC-finalize_on_demand is nonzero, it must be called  */
        /* explicitly.                                          */

/* GC_set_warn_proc can be used to redirect or filter warning messages. */
/* p may not be a NULL pointer.                                         */
typedef void (*GC_warn_proc) GC_PROTO((char *msg, GC_word arg));
GC_API GC_warn_proc GC_set_warn_proc GC_PROTO((GC_warn_proc p));
    /* Returns old warning procedure.   */

GC_API GC_word GC_set_free_space_divisor GC_PROTO((GC_word value));
    /* Set free_space_divisor.  See above for definition.       */
    /* Returns old value.                                       */
        
/* The following is intended to be used by a higher level       */
/* (e.g. Java-like) finalization facility.  It is expected      */
/* that finalization code will arrange for hidden pointers to   */
/* disappear.  Otherwise objects can be accessed after they     */
/* have been collected.                                         */
/* Note that putting pointers in atomic objects or in           */
/* nonpointer slots of "typed" objects is equivalent to         */
/* disguising them in this way, and may have other advantages.  */
# if defined(I_HIDE_POINTERS) || defined(GC_I_HIDE_POINTERS)
    typedef GC_word GC_hidden_pointer;
#   define HIDE_POINTER(p) (~(GC_hidden_pointer)(p))
#   define REVEAL_POINTER(p) ((GC_PTR)(HIDE_POINTER(p)))
    /* Converting a hidden pointer to a real pointer requires verifying */
    /* that the object still exists.  This involves acquiring the       */
    /* allocator lock to avoid a race with the collector.               */
# endif /* I_HIDE_POINTERS */

typedef GC_PTR (*GC_fn_type) GC_PROTO((GC_PTR client_data));
GC_API GC_PTR GC_call_with_alloc_lock
                GC_PROTO((GC_fn_type fn, GC_PTR client_data));

/* The following routines are primarily intended for use with a         */
/* preprocessor which inserts calls to check C pointer arithmetic.      */
/* They indicate failure by invoking the corresponding _print_proc.     */

/* Check that p and q point to the same object.                 */
/* Fail conspicuously if they don't.                            */
/* Returns the first argument.                                  */
/* Succeeds if neither p nor q points to the heap.              */
/* May succeed if both p and q point to between heap objects.   */
GC_API GC_PTR GC_same_obj GC_PROTO((GC_PTR p, GC_PTR q));

/* Checked pointer pre- and post- increment operations.  Note that      */
/* the second argument is in units of bytes, not multiples of the       */
/* object size.  This should either be invoked from a macro, or the     */
/* call should be automatically generated.                              */
GC_API GC_PTR GC_pre_incr GC_PROTO((GC_PTR *p, size_t how_much));
GC_API GC_PTR GC_post_incr GC_PROTO((GC_PTR *p, size_t how_much));

/* Check that p is visible                                              */
/* to the collector as a possibly pointer containing location.          */
/* If it isn't fail conspicuously.                                      */
/* Returns the argument in all cases.  May erroneously succeed          */
/* in hard cases.  (This is intended for debugging use with             */
/* untyped allocations.  The idea is that it should be possible, though */
/* slow, to add such a call to all indirect pointer stores.)            */
/* Currently useless for multithreaded worlds.                          */
GC_API GC_PTR GC_is_visible GC_PROTO((GC_PTR p));

/* Check that if p is a pointer to a heap page, then it points to       */
/* a valid displacement within a heap object.                           */
/* Fail conspicuously if this property does not hold.                   */
/* Uninteresting with GC_all_interior_pointers.                         */
/* Always returns its argument.                                         */
GC_API GC_PTR GC_is_valid_displacement GC_PROTO((GC_PTR p));

/* Returns 1 if the calling thread is registered with the GC, 0 otherwise */
GC_API int GC_thread_is_registered GC_PROTO((void));

/* Safer, but slow, pointer addition.  Probably useful mainly with      */
/* a preprocessor.  Useful only for heap pointers.                      */
#ifdef GC_DEBUG
#   define GC_PTR_ADD3(x, n, type_of_result) \
        ((type_of_result)GC_same_obj((x)+(n), (x)))
#   define GC_PRE_INCR3(x, n, type_of_result) \
        ((type_of_result)GC_pre_incr(&(x), (n)*sizeof(*x))
#   define GC_POST_INCR2(x, type_of_result) \
        ((type_of_result)GC_post_incr(&(x), sizeof(*x))
#   ifdef __GNUC__
#       define GC_PTR_ADD(x, n) \
            GC_PTR_ADD3(x, n, typeof(x))
#       define GC_PRE_INCR(x, n) \
            GC_PRE_INCR3(x, n, typeof(x))
#       define GC_POST_INCR(x, n) \
            GC_POST_INCR3(x, typeof(x))
#   else
        /* We can't do this right without typeof, which ANSI    */
        /* decided was not sufficiently useful.  Repeatedly     */
        /* mentioning the arguments seems too dangerous to be   */
        /* useful.  So does not casting the result.             */
#       define GC_PTR_ADD(x, n) ((x)+(n))
#   endif
#else   /* !GC_DEBUG */
#   define GC_PTR_ADD3(x, n, type_of_result) ((x)+(n))
#   define GC_PTR_ADD(x, n) ((x)+(n))
#   define GC_PRE_INCR3(x, n, type_of_result) ((x) += (n))
#   define GC_PRE_INCR(x, n) ((x) += (n))
#   define GC_POST_INCR2(x, n, type_of_result) ((x)++)
#   define GC_POST_INCR(x, n) ((x)++)
#endif

/* Safer assignment of a pointer to a nonstack location.        */
#ifdef GC_DEBUG
# if defined(__STDC__) || defined(_AIX)
#   define GC_PTR_STORE(p, q) \
        (*(void **)GC_is_visible(p) = GC_is_valid_displacement(q))
# else
#   define GC_PTR_STORE(p, q) \
        (*(char **)GC_is_visible(p) = GC_is_valid_displacement(q))
# endif
#else /* !GC_DEBUG */
#   define GC_PTR_STORE(p, q) *((p) = (q))
#endif

/* Functions called to report pointer checking errors */
GC_API void (*GC_same_obj_print_proc) GC_PROTO((GC_PTR p, GC_PTR q));

GC_API void (*GC_is_valid_displacement_print_proc)
        GC_PROTO((GC_PTR p));

GC_API void (*GC_is_visible_print_proc)
        GC_PROTO((GC_PTR p));

/* For pthread support, we generally need to intercept a number of      */
/* thread library calls.  We do that here by macro defining them.       */

#if !defined(GC_USE_LD_WRAP) && \
    (defined(GC_PTHREADS) || defined(GC_SOLARIS_THREADS) || defined(GC_DARWIN_THREADS) || defined(GC_MACOSX_THREADS))
#if defined(_IN_LIBGC) || defined(USE_INCLUDED_LIBGC)
# include "gc_pthread_redirects.h"
#else
# include <gc/gc_pthread_redirects.h>
#endif
#endif

# if defined(PCR) || defined(GC_SOLARIS_THREADS) || \
     defined(GC_PTHREADS) || defined(GC_WIN32_THREADS)
        /* Any flavor of threads except SRC_M3. */
/* This returns a list of objects, linked through their first           */
/* word.  Its use can greatly reduce lock contention problems, since    */
/* the allocation lock can be acquired and released many fewer times.   */
/* lb must be large enough to hold the pointer field.                   */
/* It is used internally by gc_local_alloc.h, which provides a simpler  */
/* programming interface on Linux.                                      */
GC_PTR GC_malloc_many(size_t lb);
#define GC_NEXT(p) (*(GC_PTR *)(p))     /* Retrieve the next element    */
                                        /* in returned list.            */
extern void GC_thr_init(void);  /* Needed for Solaris/X86       */

#endif /* THREADS && !SRC_M3 */

#if defined(GC_WIN32_THREADS) && !defined(__CYGWIN32__) && !defined(__CYGWIN__)
# include <windows.h>

   BOOL WINAPI GC_DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved);

  /*
   * All threads must be created using GC_CreateThread, so that they will be
   * recorded in the thread table.  For backwards compatibility, this is not
   * technically true if the GC is built as a dynamic library, since it can
   * and does then use DllMain to keep track of thread creations.  But new code
   * should be built to call GC_CreateThread.
   */
   GC_API HANDLE WINAPI GC_CreateThread(
      LPSECURITY_ATTRIBUTES lpThreadAttributes,
      DWORD dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress,
      LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId );

# if defined(_WIN32_WCE)
  /*
   * win32_threads.c implements the real WinMain, which will start a new thread
   * to call GC_WinMain after initializing the garbage collector.
   */
  int WINAPI GC_WinMain(
      HINSTANCE hInstance,
      HINSTANCE hPrevInstance,
      LPWSTR lpCmdLine,
      int nCmdShow );

#  ifndef GC_BUILD
#    define WinMain GC_WinMain
#    define CreateThread GC_CreateThread
#  endif
# endif /* defined(_WIN32_WCE) */

#endif /* defined(GC_WIN32_THREADS)  && !cygwin */

 /*
  * Fully portable code should call GC_INIT() from the main program
  * before making any other GC_ calls.  On most platforms this is a
  * no-op and the collector self-initializes.  But a number of platforms
  * make that too hard.
  */
#if (defined(sparc) || defined(__sparc)) && defined(sun)
    /*
     * If you are planning on putting
     * the collector in a SunOS 5 dynamic library, you need to call GC_INIT()
     * from the statically loaded program section.
     * This circumvents a Solaris 2.X (X<=4) linker bug.
     */
#   define GC_INIT() { extern end, etext; \
                       GC_noop(&end, &etext); }
#else
# if defined(__CYGWIN32__) || defined (_AIX)
    /*
     * Similarly gnu-win32 DLLs need explicit initialization from
     * the main program, as does AIX.
     */
#   ifdef __CYGWIN32__
      extern int _data_start__[];
      extern int _data_end__[];
      extern int _bss_start__[];
      extern int _bss_end__[];
#     define GC_MAX(x,y) ((x) > (y) ? (x) : (y))
#     define GC_MIN(x,y) ((x) < (y) ? (x) : (y))
#     define GC_DATASTART ((GC_PTR) GC_MIN(_data_start__, _bss_start__))
#     define GC_DATAEND  ((GC_PTR) GC_MAX(_data_end__, _bss_end__))
#     ifdef GC_DLL
#       define GC_INIT() { GC_add_roots(GC_DATASTART, GC_DATAEND); }
#     else
#       define GC_INIT()
#     endif
#   endif
#   if defined(_AIX)
      extern int _data[], _end[];
#     define GC_DATASTART ((GC_PTR)((ulong)_data))
#     define GC_DATAEND ((GC_PTR)((ulong)_end))
#     define GC_INIT() { GC_add_roots(GC_DATASTART, GC_DATAEND); }
#   endif
# else
#  if defined(__APPLE__) && defined(__MACH__) || defined(GC_WIN32_THREADS)
#   define GC_INIT() { GC_init(); }
#  else
#   define GC_INIT()
#  endif /* !__MACH && !GC_WIN32_THREADS */
# endif /* !AIX && !cygwin */
#endif /* !sparc */

#if !defined(_WIN32_WCE) \
    && ((defined(_MSDOS) || defined(_MSC_VER)) && (_M_IX86 >= 300) \
        || defined(_WIN32) && !defined(__CYGWIN32__) && !defined(__CYGWIN__))
  /* win32S may not free all resources on process exit.  */
  /* This explicitly deallocates the heap.               */
    GC_API void GC_win32_free_heap ();
#endif

#if ( defined(_AMIGA) && !defined(GC_AMIGA_MAKINGLIB) )
  /* Allocation really goes through GC_amiga_allocwrapper_do */
# include "gc_amiga_redirects.h"
#endif

#if defined(GC_REDIRECT_TO_LOCAL) && !defined(GC_LOCAL_ALLOC_H)
#  include  "gc_local_alloc.h"
#endif

#ifdef __cplusplus
    }  /* end of extern "C" */
#endif

#endif /* _GC_H */