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only use memcpy realloc to shrink if an exact-sized free chunk exists

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otherwise, shrink in-place. as explained in the description of commit
3e16313f8f, the split here is valid
without holding split_merge_lock because all chunks involved are in
the in-use state.
This commit is contained in:
Rich Felker 2020-06-16 00:53:57 -04:00
parent cb5babdc8d
commit fca7428c09
1 changed files with 12 additions and 0 deletions
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12
src/malloc/oldmalloc/malloc.c
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@ -385,6 +385,18 @@ void *realloc(void *p, size_t n)
/* Crash on corrupted footer (likely from buffer overflow) */
if (next->psize != self->csize) a_crash();
if (n < n0) {
int i = bin_index_up(n);
int j = bin_index(n0);
if (i<j && (mal.binmap & (1ULL << i)))
goto copy_realloc;
struct chunk *split = (void *)((char *)self + n);
self->csize = split->psize = n | C_INUSE;
split->csize = next->psize = n0-n | C_INUSE;
__bin_chunk(split);
return CHUNK_TO_MEM(self);
}
lock(mal.split_merge_lock);
size_t nsize = next->csize & C_INUSE ? 0 : CHUNK_SIZE(next);