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support: Do not require overflow builtin in support/blob_repeat.c

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It is only available in GCC 5 and later.

Tested-by: Romain Naour <romain.naour@gmail.com>
(cherry picked from commit 0c1719e65b)
This commit is contained in:
Florian Weimer 2018-12-15 18:58:09 +01:00
parent 4d7af7815a
commit 1a8db070fa
2 changed files with 29 additions and 3 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2018-12-15 Florian Weimer <fweimer@redhat.com>
* support/blob_repeat.c (check_mul_overflow_size_t): New function.
(minimum_stride_size): Use it.
(support_blob_repeat_allocate): Likewise.
2018-12-13 Andreas Schwab <schwab@suse.de>
[BZ #23861]

26
support/blob_repeat.c
View File

@ -34,6 +34,26 @@
optimization because mappings carry a lot of overhead. */
static const size_t maximum_small_size = 4 * 1024 * 1024;
/* Set *RESULT to LEFT * RIGHT. Return true if the multiplication
overflowed. See <malloc/malloc-internal.h>. */
static inline bool
check_mul_overflow_size_t (size_t left, size_t right, size_t *result)
{
#if __GNUC__ >= 5
return __builtin_mul_overflow (left, right, result);
#else
/* size_t is unsigned so the behavior on overflow is defined. */
*result = left * right;
size_t half_size_t = ((size_t) 1) << (8 * sizeof (size_t) / 2);
if (__glibc_unlikely ((left | right) >= half_size_t))
{
if (__glibc_unlikely (right != 0 && *result / right != left))
return true;
}
return false;
#endif
}
/* Internal helper for fill. */
static void
fill0 (char *target, const char *element, size_t element_size,
@ -118,8 +138,8 @@ minimum_stride_size (size_t page_size, size_t element_size)
common multiple, it appears only once. Therefore, shift one
factor. */
size_t multiple;
if (__builtin_mul_overflow (page_size >> common_zeros, element_size,
&multiple))
if (check_mul_overflow_size_t (page_size >> common_zeros, element_size,
&multiple))
return 0;
return multiple;
}
@ -255,7 +275,7 @@ support_blob_repeat_allocate (const void *element, size_t element_size,
size_t count)
{
size_t total_size;
if (__builtin_mul_overflow (element_size, count, &total_size))
if (check_mul_overflow_size_t (element_size, count, &total_size))
{
errno = EOVERFLOW;
return (struct support_blob_repeat) { 0 };