| From 037283cbc74739b72f36dfec827d120faa243406 Mon Sep 17 00:00:00 2001 |
| From: Florian Weimer <fweimer at redhat dot com> |
| Date: Thu, 6 Jul 2017 11:50:55 +0200 |
| Subject: [PATCH 26/26] assert: Suppress pedantic warning caused by statement |
| expression [BZ# 21242] |
| |
| On 07/05/2017 10:15 PM, Zack Weinberg wrote: |
| > On Wed, Jul 5, 2017 at 11:51 AM, Florian Weimer <fweimer@redhat.com> wrote: |
| >> On 07/05/2017 05:46 PM, Zack Weinberg wrote: |
| >>> A problem occurs to me: expressions involving VLAs _are_ evaluated |
| >>> inside sizeof. |
| >> |
| >> The type of the sizeof argument would still be int (due to the |
| >> comparison against 0), so this doesn't actually occur. |
| > |
| > I rechecked what C99 says about sizeof and VLAs, and you're right - |
| > the operand of sizeof is only evaluated when sizeof is _directly_ |
| > applied to a VLA. So this is indeed safe, but I think this wrinkle |
| > should be mentioned in the comment. Perhaps |
| > |
| > /* The first occurrence of EXPR is not evaluated due to the sizeof, |
| > but will trigger any pedantic warnings masked by the __extension__ |
| > for the second occurrence. The explicit comparison against zero |
| > ensures that sizeof is not directly applied to a function pointer or |
| > bit-field (which would be ill-formed) or VLA (which would be evaluated). */ |
| > |
| > zw |
| |
| What about the attached patch? |
| |
| Siddhesh, is this okay during the freeze? I'd like to backport it to |
| 2.25 as well. |
| |
| Thanks, |
| Florian |
| |
| assert: Suppress pedantic warning caused by statement expression |
| |
| 2017-07-06 Florian Weimer <fweimer@redhat.com> |
| |
| [BZ #21242] |
| * assert/assert.h [__GNUC__ && !__STRICT_ANSI__] (assert): |
| Suppress pedantic warning resulting from statement expression. |
| (__ASSERT_FUNCTION): Add missing __extendsion__. |
| --- |
| |
| Upstream-Status: Submitted |
| Signed-off-by: Khem Raj <raj.khem@gmail.com> |
| |
| assert/assert.h | 12 +++++++++--- |
| 1 file changed, 9 insertions(+), 3 deletions(-) |
| |
| diff --git a/assert/assert.h b/assert/assert.h |
| index 22f019537c..6801cfeb10 100644 |
| --- a/assert/assert.h |
| +++ b/assert/assert.h |
| @@ -91,13 +91,19 @@ __END_DECLS |
| ? __ASSERT_VOID_CAST (0) \ |
| : __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION)) |
| # else |
| +/* The first occurrence of EXPR is not evaluated due to the sizeof, |
| + but will trigger any pedantic warnings masked by the __extension__ |
| + for the second occurrence. The explicit comparison against zero is |
| + required to support function pointers and bit fields in this |
| + context, and to suppress the evaluation of variable length |
| + arrays. */ |
| # define assert(expr) \ |
| - ({ \ |
| + ((void) sizeof ((expr) == 0), __extension__ ({ \ |
| if (expr) \ |
| ; /* empty */ \ |
| else \ |
| __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION); \ |
| - }) |
| + })) |
| # endif |
| |
| # ifdef __USE_GNU |
| @@ -113,7 +119,7 @@ __END_DECLS |
| C9x has a similar variable called __func__, but prefer the GCC one since |
| it demangles C++ function names. */ |
| # if defined __cplusplus ? __GNUC_PREREQ (2, 6) : __GNUC_PREREQ (2, 4) |
| -# define __ASSERT_FUNCTION __PRETTY_FUNCTION__ |
| +# define __ASSERT_FUNCTION __extension__ __PRETTY_FUNCTION__ |
| # else |
| # if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L |
| # define __ASSERT_FUNCTION __func__ |
| -- |
| 2.13.3 |
| |