* config/xtensa/xtensa.c: Formatting.
[official-gcc.git] / boehm-gc / include / gc_backptr.h
blob5899496e0fe59db1065ca13d3b681abffdba8499
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"
6 * This API assumes that we have an ANSI C compiler.
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.
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.
17 * Results are likely to be much more useful if all allocation is
18 * accomplished through the debugging allocators.
20 * The implementation idea is due to A. Demers.
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;
43 GC_ref_kind GC_get_back_ptr_info(void *dest, void **base_p, size_t *offset_p);
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);
50 /* Generate a random address inside a valid marked heap object. */
51 void * GC_generate_random_valid_address(void);
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);
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 *);
65 #endif /* GC_BACKPTR_H */