2 * Copyright (c) 1994 by Xerox Corporation. All rights reserved.
3 * Copyright (c) 1996 by Silicon Graphics. All rights reserved.
4 * Copyright (c) 1998 by Fergus Henderson. All rights reserved.
5 * Copyright (c) 2000-2009 by Hewlett-Packard Development Company.
8 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
9 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
11 * Permission is hereby granted to use or copy this program
12 * for any purpose, provided the above notices are retained on all copies.
13 * Permission to modify the code and to distribute modified code is granted,
14 * provided the above notices are retained, and a notice that the code was
15 * modified is included with the above copyright notice.
19 * This is a simple API to implement pointer back tracing, i.e.
20 * to answer questions such as "who is pointing to this" or
21 * "why is this object being retained by the collector"
23 * This API assumes that we have an ANSI C compiler.
25 * Most of these calls yield useful information on only after
26 * a garbage collection. Usually the client will first force
27 * a full collection and then gather information, preferably
28 * before much intervening allocation.
30 * The implementation of the interface is only about 99.9999%
31 * correct. It is intended to be good enough for profiling,
32 * but is not intended to be used with production code.
34 * Results are likely to be much more useful if all allocation is
35 * accomplished through the debugging allocators.
37 * The implementation idea is due to A. Demers.
51 /* Store information about the object referencing dest in *base_p */
53 /* If multiple objects or roots point to dest, the one reported */
54 /* will be the last on used by the garbage collector to trace the */
56 /* source is root ==> *base_p = address, *offset_p = 0 */
57 /* source is heap object ==> *base_p != 0, *offset_p = offset */
58 /* Returns 1 on success, 0 if source couldn't be determined. */
59 /* Dest can be any address within a heap object. */
61 GC_UNREFERENCED, /* No reference info available. */
62 GC_NO_SPACE, /* Dest not allocated with debug alloc. */
63 GC_REFD_FROM_ROOT, /* Referenced directly by root *base_p. */
64 GC_REFD_FROM_REG, /* Referenced from a register, i.e. */
65 /* a root without an address. */
66 GC_REFD_FROM_HEAP, /* Referenced from another heap obj. */
67 GC_FINALIZER_REFD /* Finalizable and hence accessible. */
70 GC_API GC_ref_kind GC_CALL GC_get_back_ptr_info(void * /* dest */,
72 size_t * /* offset_p */);
74 /* Generate a random heap address. */
75 /* The resulting address is in the heap, but */
76 /* not necessarily inside a valid object. */
77 GC_API void * GC_CALL GC_generate_random_heap_address(void);
79 /* Generate a random address inside a valid marked heap object. */
80 GC_API void * GC_CALL GC_generate_random_valid_address(void);
82 /* Force a garbage collection and generate a backtrace from a */
83 /* random heap address. */
84 /* This uses the GC logging mechanism (GC_printf) to produce */
85 /* output. It can often be called from a debugger. The */
86 /* source in dbg_mlc.c also serves as a sample client. */
87 GC_API void GC_CALL GC_generate_random_backtrace(void);
89 /* Print a backtrace from a specific address. Used by the */
90 /* above. The client should call GC_gcollect() immediately */
91 /* before invocation. */
92 GC_API void GC_CALL GC_print_backtrace(void *);
95 } /* end of extern "C" */
98 #endif /* GC_BACKPTR_H */