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MINOR: memprof: add one pointer size to the size of allocations

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The current model causes an issue when trying to spot memory leaks,
because malloc(0) or realloc(0) do not count as allocations since we only
account for the application-usable size. This is the problem that made
issue #1406 not to appear as a leak.

What we're doing now is to account for one extra pointer (the one that
memory allocators usually place before the returned area), so that a
malloc(0) will properly account for 4 or 8 bytes. We don't need something
exact, we just need something non-zero so that a realloc(X) followed by a
realloc(0) without a free() gives a small non-zero result.

It was verified that the results are stable including in the presence
of lots of malloc/realloc/free as happens when stressing Lua.

It would make sense to backport this to 2.4 as it helps in bug reports.
This commit is contained in:
Willy Tarreau 2021-10-22 16:33:53 +02:00
parent 8cce4d79ff
commit 1de51eb727
1 changed files with 7 additions and 3 deletions
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10
src/activity.c
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@ -241,7 +241,7 @@ void *malloc(size_t size)
return memprof_malloc_handler(size);
ret = memprof_malloc_handler(size);
size = malloc_usable_size(ret);
size = malloc_usable_size(ret) + sizeof(void *);
bin = memprof_get_bin(__builtin_return_address(0), MEMPROF_METH_MALLOC);
_HA_ATOMIC_ADD(&bin->alloc_calls, 1);
@ -266,7 +266,7 @@ void *calloc(size_t nmemb, size_t size)
return memprof_calloc_handler(nmemb, size);
ret = memprof_calloc_handler(nmemb, size);
size = malloc_usable_size(ret);
size = malloc_usable_size(ret) + sizeof(void *);
bin = memprof_get_bin(__builtin_return_address(0), MEMPROF_METH_CALLOC);
_HA_ATOMIC_ADD(&bin->alloc_calls, 1);
@ -297,6 +297,10 @@ void *realloc(void *ptr, size_t size)
ret = memprof_realloc_handler(ptr, size);
size = malloc_usable_size(ret);
/* only count the extra link for new allocations */
if (!ptr)
size += sizeof(void *);
bin = memprof_get_bin(__builtin_return_address(0), MEMPROF_METH_REALLOC);
if (size > size_before) {
_HA_ATOMIC_ADD(&bin->alloc_calls, 1);
@ -329,7 +333,7 @@ void free(void *ptr)
return;
}
size_before = malloc_usable_size(ptr);
size_before = malloc_usable_size(ptr) + sizeof(void *);
memprof_free_handler(ptr);
bin = memprof_get_bin(__builtin_return_address(0), MEMPROF_METH_FREE);