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Diffstat (limited to '')
| -rw-r--r-- | gc/backptr.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/gc/backptr.h b/gc/backptr.h new file mode 100644 index 0000000..d34224e --- /dev/null +++ b/gc/backptr.h @@ -0,0 +1,56 @@ +/* + * 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. + */ + +/* 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 refence info available. */ + GC_NO_SPACE, /* Dest not allocated with debug alloc */ + GC_REFD_FROM_ROOT, /* Referenced directly by root *base_p */ + 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); + + |