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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 |