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Revert "malloc: Cleanup libc_realloc" 

This reverts commit dea1e52af3.
This commit is contained in:
Wilco Dijkstra 2025-08-04 17:31:45 +00:00
parent 8c2b6e528d
commit 1bf4a379e8
1 changed files with 15 additions and 11 deletions
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26
malloc/malloc.c
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@ -3504,17 +3504,17 @@ __libc_realloc (void *oldmem, size_t bytes)
void *newp; /* chunk to return */
/* realloc of null is supposed to be same as malloc */
if (oldmem == NULL)
return __libc_malloc (bytes);
#if REALLOC_ZERO_BYTES_FREES
if (bytes == 0)
if (bytes == 0 && oldmem != NULL)
{
__libc_free (oldmem); return NULL;
}
#endif
/* realloc of null is supposed to be same as malloc */
if (oldmem == NULL)
return __libc_malloc (bytes);
/* Perform a quick check to ensure that the pointer's tag matches the
memory's tag. */
if (__glibc_unlikely (mtag_enabled))
@ -3532,13 +3532,19 @@ __libc_realloc (void *oldmem, size_t bytes)
if (bytes <= usable)
{
size_t difference = usable - bytes;
if ((unsigned long) difference < 2 * sizeof (INTERNAL_SIZE_T))
if ((unsigned long) difference < 2 * sizeof (INTERNAL_SIZE_T)
|| (chunk_is_mmapped (oldp) && difference <= GLRO (dl_pagesize)))
return oldmem;
}
/* its size */
const INTERNAL_SIZE_T oldsize = chunksize (oldp);
if (chunk_is_mmapped (oldp))
ar_ptr = NULL;
else
ar_ptr = arena_for_chunk (oldp);
/* Little security check which won't hurt performance: the allocator
never wraps around at the end of the address space. Therefore
we can exclude some size values which might appear here by
@ -3571,9 +3577,9 @@ __libc_realloc (void *oldmem, size_t bytes)
return tag_new_usable (newmem);
}
#endif
/* Return if shrinking and mremap was unsuccessful. */
if (bytes <= usable)
return oldmem;
/* Note the extra SIZE_SZ overhead. */
if (oldsize - SIZE_SZ >= nb)
return oldmem; /* do nothing */
/* Must alloc, copy, free. */
newmem = __libc_malloc (bytes);
@ -3585,8 +3591,6 @@ __libc_realloc (void *oldmem, size_t bytes)
return newmem;
}
ar_ptr = arena_for_chunk (oldp);
if (SINGLE_THREAD_P)
{
newp = _int_realloc (ar_ptr, oldp, oldsize, nb);