glibc 2.29: Reminder, only ~3 weeks to freeze!
Commit Message
* Romain Naour:
> Hi Carlos, Joseph,
>
> Le 14/12/2018 à 22:14, Joseph Myers a écrit :
>> On Fri, 14 Dec 2018, Romain Naour wrote:
>>
>>> Actually there is a regression when the toolchain is built with glibc 2.29 and
>>> gcc 4.9 (when USE_ATOMIC_COMPILER_BUILTINS is not defined):
>>
>> What platform is this on?
>
> It's on x86 platform.
>
> There is another issue x86_64 with GCC 4.9:
>
> blob_repeat.c:121:3: error: implicit declaration of function
> '__builtin_mul_overflow' [-Werror=implicit-function-declaration]
> if (__builtin_mul_overflow (page_size >> common_zeros, element_size,
> ^
We should fix that because it's been backported to the release
branches. Please try the patch below.
Thanks,
Florian
-----
Subject: support: Do not require overflow builtin in support/blob_repeat.c
It is only available in GCC 5 and later.
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.
Comments
Hi Florian,
Le 15/12/2018 à 16:23, Florian Weimer a écrit :
> * Romain Naour:
>
>> Hi Carlos, Joseph,
>>
>> Le 14/12/2018 à 22:14, Joseph Myers a écrit :
>>> On Fri, 14 Dec 2018, Romain Naour wrote:
>>>
>>>> Actually there is a regression when the toolchain is built with glibc 2.29 and
>>>> gcc 4.9 (when USE_ATOMIC_COMPILER_BUILTINS is not defined):
>>>
>>> What platform is this on?
>>
>> It's on x86 platform.
>>
>> There is another issue x86_64 with GCC 4.9:
>>
>> blob_repeat.c:121:3: error: implicit declaration of function
>> '__builtin_mul_overflow' [-Werror=implicit-function-declaration]
>> if (__builtin_mul_overflow (page_size >> common_zeros, element_size,
>> ^
>
> We should fix that because it's been backported to the release
> branches. Please try the patch below.
Thanks for the patch, it fixes this issue.
Tested-by: Romain Naour <romain.naour@gmail.com>
Best regards,
Romain
>
> Thanks,
> Florian
>
> -----
> Subject: support: Do not require overflow builtin in support/blob_repeat.c
>
> It is only available in GCC 5 and later.
>
> 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.
>
> diff --git a/support/blob_repeat.c b/support/blob_repeat.c
> index 16c1e448b9..718846d81d 100644
> --- a/support/blob_repeat.c
> +++ b/support/blob_repeat.c
> @@ -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 };
>
@@ -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 };