/
__libc_calloc.c
142 lines (123 loc) · 3.3 KB
/
__libc_calloc.c
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void *
__libc_calloc (size_t n, size_t elem_size)
{
mstate av;
mchunkptr oldtop, p;
INTERNAL_SIZE_T bytes, sz, csz, oldtopsize;
void *mem;
unsigned long clearsize;
unsigned long nclears;
INTERNAL_SIZE_T *d;
/* size_t is unsigned so the behavior on overflow is defined. */
bytes = n * elem_size;
#define HALF_INTERNAL_SIZE_T \
(((INTERNAL_SIZE_T) 1) << (8 * sizeof (INTERNAL_SIZE_T) / 2))
if (__builtin_expect ((n | elem_size) >= HALF_INTERNAL_SIZE_T, 0))
{
if (elem_size != 0 && bytes / elem_size != n)
{
__set_errno (ENOMEM);
return 0;
}
}
void *(*hook) (size_t, const void *) =
atomic_forced_read (__malloc_hook);
if (__builtin_expect (hook != NULL, 0))
{
sz = bytes;
mem = (*hook)(sz, RETURN_ADDRESS (0));
if (mem == 0)
return 0;
return memset (mem, 0, sz);
}
sz = bytes;
arena_get (av, sz);
if (av)
{
/* Check if we hand out the top chunk, in which case there may be no
need to clear. */
#if MORECORE_CLEARS
oldtop = top (av);
oldtopsize = chunksize (top (av));
# if MORECORE_CLEARS < 2
/* Only newly allocated memory is guaranteed to be cleared. */
if (av == &main_arena &&
oldtopsize < mp_.sbrk_base + av->max_system_mem - (char *) oldtop)
oldtopsize = (mp_.sbrk_base + av->max_system_mem - (char *) oldtop);
# endif
if (av != &main_arena)
{
heap_info *heap = heap_for_ptr (oldtop);
if (oldtopsize < (char *) heap + heap->mprotect_size - (char *) oldtop)
oldtopsize = (char *) heap + heap->mprotect_size - (char *) oldtop;
}
#endif
}
else
{
/* No usable arenas. */
oldtop = 0;
oldtopsize = 0;
}
mem = _int_malloc (av, sz);
assert (!mem || chunk_is_mmapped (mem2chunk (mem)) ||
av == arena_for_chunk (mem2chunk (mem)));
if (mem == 0 && av != NULL)
{
LIBC_PROBE (memory_calloc_retry, 1, sz);
av = arena_get_retry (av, sz);
mem = _int_malloc (av, sz);
}
if (av != NULL)
(void) mutex_unlock (&av->mutex);
/* Allocation failed even after a retry. */
if (mem == 0)
return 0;
p = mem2chunk (mem);
/* Two optional cases in which clearing not necessary */
if (chunk_is_mmapped (p))
{
if (__builtin_expect (perturb_byte, 0))
return memset (mem, 0, sz);
return mem;
}
csz = chunksize (p);
#if MORECORE_CLEARS
if (perturb_byte == 0 && (p == oldtop && csz > oldtopsize))
{
/* clear only the bytes from non-freshly-sbrked memory */
csz = oldtopsize;
}
#endif
/* Unroll clear of <= 36 bytes (72 if 8byte sizes). We know that
contents have an odd number of INTERNAL_SIZE_T-sized words;
minimally 3. */
d = (INTERNAL_SIZE_T *) mem;
clearsize = csz - SIZE_SZ;
nclears = clearsize / sizeof (INTERNAL_SIZE_T);
assert (nclears >= 3);
if (nclears > 9)
return memset (d, 0, clearsize);
else
{
*(d + 0) = 0;
*(d + 1) = 0;
*(d + 2) = 0;
if (nclears > 4)
{
*(d + 3) = 0;
*(d + 4) = 0;
if (nclears > 6)
{
*(d + 5) = 0;
*(d + 6) = 0;
if (nclears > 8)
{
*(d + 7) = 0;
*(d + 8) = 0;
}
}
}
}
return mem;
}