[thirdparty/gcc.git] / boehm-gc / include / gc_backptr.h

/*
 * This is a simple API to implement pointer back tracing, i.e.
 * to answer questions such as "who is pointing to this" or
 * "why is this object being retained by the collector"
 *
 * This API assumes that we have an ANSI C compiler.
 *
 * Most of these calls yield useful information on only after
 * a garbage collection.  Usually the client will first force
 * a full collection and then gather information, preferably
 * before much intervening allocation.
 *
 * The implementation of the interface is only about 99.9999%
 * correct.  It is intended to be good enough for profiling,
 * but is not intended to be used with production code.
 *
 * Results are likely to be much more useful if all allocation is
 * accomplished through the debugging allocators.
 *
 * The implementation idea is due to A. Demers.
 */

#ifndef GC_BACKPTR_H
#define GC_BACKPTR_H
/* Store information about the object referencing dest in *base_p     */
/* and *offset_p.                                                     */
/* If multiple objects or roots point to dest, the one reported	      */
/* will be the last on used by the garbage collector to trace the     */
/* object.							      */
/*   source is root ==> *base_p = address, *offset_p = 0	      */
/*   source is heap object ==> *base_p != 0, *offset_p = offset       */
/*   Returns 1 on success, 0 if source couldn't be determined.        */
/* Dest can be any address within a heap object.                      */
typedef enum {  GC_UNREFERENCED, /* No reference info available.	*/
		GC_NO_SPACE,	/* Dest not allocated with debug alloc  */
		GC_REFD_FROM_ROOT, /* Referenced directly by root *base_p */
		GC_REFD_FROM_REG,  /* Referenced from a register, i.e.	*/
				   /* a root without an address.	*/
		GC_REFD_FROM_HEAP, /* Referenced from another heap obj. */
		GC_FINALIZER_REFD /* Finalizable and hence accessible.  */
} GC_ref_kind;

GC_ref_kind GC_get_back_ptr_info(void *dest, void **base_p, size_t *offset_p);

/* Generate a random heap address.            */
/* The resulting address is in the heap, but  */
/* not necessarily inside a valid object.     */
void * GC_generate_random_heap_address(void);

/* Generate a random address inside a valid marked heap object. */
void * GC_generate_random_valid_address(void);

/* Force a garbage collection and generate a backtrace from a */
/* random heap address.                                       */
/* This uses the GC logging mechanism (GC_printf) to produce  */
/* output.  It can often be called from a debugger.  The      */
/* source in dbg_mlc.c also serves as a sample client.	      */
void GC_generate_random_backtrace(void);

/* Print a backtrace from a specific address.  Used by the 	*/
/* above.  The client should call GC_gcollect() immediately	*/
/* before invocation.						*/
void GC_print_backtrace(void *);

#endif /* GC_BACKPTR_H */
Commit	Line	Data
f54d4287 BM	1	/*
	2	* This is a simple API to implement pointer back tracing, i.e.
	3	* to answer questions such as "who is pointing to this" or
	4	* "why is this object being retained by the collector"
	5	*
	6	* This API assumes that we have an ANSI C compiler.
	7	*
	8	* Most of these calls yield useful information on only after
	9	* a garbage collection. Usually the client will first force
	10	* a full collection and then gather information, preferably
	11	* before much intervening allocation.
	12	*
	13	* The implementation of the interface is only about 99.9999%
	14	* correct. It is intended to be good enough for profiling,
	15	* but is not intended to be used with production code.
	16	*
	17	* Results are likely to be much more useful if all allocation is
	18	* accomplished through the debugging allocators.
	19	*
	20	* The implementation idea is due to A. Demers.
	21	*/
	22
	23	#ifndef GC_BACKPTR_H
	24	#define GC_BACKPTR_H
	25	/* Store information about the object referencing dest in base_p /
	26	/* and offset_p. /
	27	/* If multiple objects or roots point to dest, the one reported */
	28	/* will be the last on used by the garbage collector to trace the */
	29	/* object. */
	30	/* source is root ==> base_p = address, offset_p = 0 */
	31	/* source is heap object ==> base_p != 0, offset_p = offset */
	32	/* Returns 1 on success, 0 if source couldn't be determined. */
	33	/* Dest can be any address within a heap object. */
	34	typedef enum { GC_UNREFERENCED, /* No reference info available. */
	35	GC_NO_SPACE, /* Dest not allocated with debug alloc */
	36	GC_REFD_FROM_ROOT, /* Referenced directly by root base_p /
	37	GC_REFD_FROM_REG, /* Referenced from a register, i.e. */
	38	/* a root without an address. */
	39	GC_REFD_FROM_HEAP, /* Referenced from another heap obj. */
	40	GC_FINALIZER_REFD /* Finalizable and hence accessible. */
	41	} GC_ref_kind;
	42
	43	GC_ref_kind GC_get_back_ptr_info(void dest, void base_p, size_t offset_p);
	44
	45	/* Generate a random heap address. */
	46	/* The resulting address is in the heap, but */
	47	/* not necessarily inside a valid object. */
	48	void * GC_generate_random_heap_address(void);
	49
	50	/* Generate a random address inside a valid marked heap object. */
	51	void * GC_generate_random_valid_address(void);
	52
	53	/* Force a garbage collection and generate a backtrace from a */
	54	/* random heap address. */
	55	/* This uses the GC logging mechanism (GC_printf) to produce */
	56	/* output. It can often be called from a debugger. The */
	57	/* source in dbg_mlc.c also serves as a sample client. */
	58	void GC_generate_random_backtrace(void);
	59
	60	/* Print a backtrace from a specific address. Used by the */
	61	/* above. The client should call GC_gcollect() immediately */
	62	/* before invocation. */
	63	void GC_print_backtrace(void *);
	64
65	#endif /* GC_BACKPTR_H */