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Annotation of OpenXM_contrib/gc/backptr.h, Revision 1.1

1.1     ! maekawa     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: /* Store information about the object referencing dest in *base_p     */
        !            24: /* and *offset_p.                                                     */
        !            25: /* If multiple objects or roots point to dest, the one reported              */
        !            26: /* will be the last on used by the garbage collector to trace the     */
        !            27: /* object.                                                           */
        !            28: /*   source is root ==> *base_p = address, *offset_p = 0             */
        !            29: /*   source is heap object ==> *base_p != 0, *offset_p = offset       */
        !            30: /*   Returns 1 on success, 0 if source couldn't be determined.        */
        !            31: /* Dest can be any address within a heap object.                      */
        !            32: typedef enum {  GC_UNREFERENCED, /* No refence info available.         */
        !            33:                GC_NO_SPACE,    /* Dest not allocated with debug alloc  */
        !            34:                GC_REFD_FROM_ROOT, /* Referenced directly by root *base_p */
        !            35:                GC_REFD_FROM_HEAP, /* Referenced from another heap obj. */
        !            36:                GC_FINALIZER_REFD /* Finalizable and hence accessible.  */
        !            37: } GC_ref_kind;
        !            38:
        !            39: GC_ref_kind GC_get_back_ptr_info(void *dest, void **base_p, size_t *offset_p);
        !            40:
        !            41: /* Generate a random heap address.            */
        !            42: /* The resulting address is in the heap, but  */
        !            43: /* not necessarily inside a valid object.     */
        !            44: void * GC_generate_random_heap_address(void);
        !            45:
        !            46: /* Generate a random address inside a valid marked heap object. */
        !            47: void * GC_generate_random_valid_address(void);
        !            48:
        !            49: /* Force a garbage collection and generate a backtrace from a */
        !            50: /* random heap address.                                       */
        !            51: /* This uses the GC logging mechanism (GC_printf) to produce  */
        !            52: /* output.  It can often be called from a debugger.  The      */
        !            53: /* source in dbg_mlc.c also serves as a sample client.       */
        !            54: void GC_generate_random_backtrace(void);
        !            55:
        !            56: