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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/94444] __attribute__((access(...))) ignored for memcpy when compiling with -Os Date: Wed, 01 Apr 2020 16:05:35 +0000 [thread overview] Message-ID: <bug-94444-4-j9AddW8XSs@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-94444-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94444 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2020-04-01 CC| |msebor at gcc dot gnu.org Ever confirmed|0 |1 Status|UNCONFIRMED |WAITING --- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> --- Can you include a small test case that reproduce the problem (and the full command line used to reproduce it)? I can't think of a reason why the attribute would be completely ineffective with -Os and a simple test case confirms it does the right thing even with with -fno-builtin-memcpy (if the built-in happens to be disabled while building libc). GCC recognizes __builtin_memcpy as special (built-ins aren't decorated with the attribute in GCC 10) so it should have the same detection as functions explicitly declared with the attribute. $ cat z.c && gcc -Os -S -fno-builtin-memcpy z.c __attribute__ ((access (write_only, 1, 3), access (read_only, 2, 3))) void* memcpy (void*, const void*, __SIZE_TYPE__); char a[3]; void f (const void *s) { memcpy (a, s, 5); } void g (const void *s) { __builtin_memcpy (a, s, 5); } z.c: In function ‘f’: z.c:8:3: warning: ‘memcpy’ writing 5 bytes into a region of size 3 overflows the destination [-Wstringop-overflow=] 8 | memcpy (a, s, 5); | ^~~~~~~~~~~~~~~~ z.c:2:7: note: in a call to function ‘memcpy’ declared with attribute ‘write_only (1, 3)’ 2 | void* memcpy (void*, const void*, __SIZE_TYPE__); | ^~~~~~ z.c: In function ‘g’: z.c:13:3: warning: ‘__builtin_memcpy’ writing 5 bytes into a region of size 3 overflows the destination [-Wstringop-overflow=] 13 | __builtin_memcpy (a, s, 5); | ^~~~~~~~~~~~~~~~~~~~~~~~~~
next prev parent reply other threads:[~2020-04-01 16:05 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-01 15:31 [Bug c/94444] New: " felix-gcc at fefe dot de 2020-04-01 15:49 ` [Bug c/94444] " jakub at gcc dot gnu.org 2020-04-01 16:05 ` msebor at gcc dot gnu.org [this message] 2020-04-01 17:04 ` rguenth at gcc dot gnu.org 2020-04-01 17:17 ` felix-gcc at fefe dot de 2020-04-01 19:46 ` msebor at gcc dot gnu.org
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