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malloc: Cleanup libc_realloc

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Minor cleanup of libc_realloc: remove unnecessary special cases for mmap, move
ar_ptr initialization, first check for oldmem == NULL.
This commit is contained in:
Wilco Dijkstra
2025-05-28 15:17:43 +00:00
parent 4b74591022
commit dea1e52af3
1 changed files with 11 additions and 15 deletions
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26
malloc/malloc.c
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@@ -3501,17 +3501,17 @@ __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 && oldmem != NULL)
if (bytes == 0)
{
__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))
@@ -3529,19 +3529,13 @@ __libc_realloc (void *oldmem, size_t bytes)
if (bytes <= usable)
{
size_t difference = usable - bytes;
if ((unsigned long) difference < 2 * sizeof (INTERNAL_SIZE_T)
|| (chunk_is_mmapped (oldp) && difference <= GLRO (dl_pagesize)))
if ((unsigned long) difference < 2 * sizeof (INTERNAL_SIZE_T))
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
@@ -3574,9 +3568,9 @@ __libc_realloc (void *oldmem, size_t bytes)
return tag_new_usable (newmem);
}
#endif
/* Note the extra SIZE_SZ overhead. */
if (oldsize - SIZE_SZ >= nb)
return oldmem; /* do nothing */
/* Return if shrinking and mremap was unsuccessful. */
if (bytes <= usable)
return oldmem;
/* Must alloc, copy, free. */
newmem = __libc_malloc (bytes);
@@ -3588,6 +3582,8 @@ __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);