From patchwork Tue Nov 25 13:01:37 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 3899 Received: (qmail 9299 invoked by alias); 25 Nov 2014 13:01:49 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 9287 invoked by uid 89); 25 Nov 2014 13:01:48 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.3 required=5.0 tests=AWL, BAYES_00, SPF_HELO_PASS, SPF_PASS, T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Date: Tue, 25 Nov 2014 18:31:37 +0530 From: Siddhesh Poyarekar To: libc-alpha@sourceware.org Cc: carlos@redhat.com, jakub@redhat.com Subject: [PATCH] Don't use __warn_memset_zero_len for gcc-5.0 or newer Message-ID: <20141125130137.GN12197@spoyarek.pnq.redhat.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.22.1-rc1 (2013-10-16) Hi, gcc now warns when the arguments to memset may have been accidentally transposed (i.e. length set to zero instead of the byte), so we don't need that bit of the code in glibc headers anymore. Tested on x86_64. Coe generated by gcc 4.8 is identical with or without the patch. I also tested gcc master, which does not result in any new failures. It does fail quite a few FORTIFY_SOURCE tests, but those failures are not due to this patch. I'll look at them deeper. OK to commit this? Siddhesh * string/bits/string3.h (__warn_memset_zero_len): Don't declare for gcc newer than 5.0. (memset): Don't test for zero-length __LEN for gcc newer than 5.0. diff --git a/string/bits/string3.h b/string/bits/string3.h index 7606090..801e7ac 100644 --- a/string/bits/string3.h +++ b/string/bits/string3.h @@ -19,8 +19,10 @@ # error "Never use directly; include instead." #endif +#if !__GNUC_PREREQ (5,0) __warndecl (__warn_memset_zero_len, "memset used with constant zero length parameter; this could be due to transposed parameters"); +#endif #ifndef __cplusplus /* XXX This is temporarily. We should not redefine any of the symbols @@ -75,12 +77,16 @@ __NTH (mempcpy (void *__restrict __dest, const void *__restrict __src, __fortify_function void * __NTH (memset (void *__dest, int __ch, size_t __len)) { + /* GCC-5.0 and newer implements these checks in the compiler, so we don't + need them here. */ +#if !__GNUC_PREREQ (5,0) if (__builtin_constant_p (__len) && __len == 0 && (!__builtin_constant_p (__ch) || __ch != 0)) { __warn_memset_zero_len (); return __dest; } +#endif return __builtin___memset_chk (__dest, __ch, __len, __bos0 (__dest)); }