public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug tree-optimization/48795] New: -Warray-bounds false positive
@ 2011-04-27 23:41 niko.lecam at gmail dot com
2011-04-27 23:43 ` [Bug tree-optimization/48795] " niko.lecam at gmail dot com
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: niko.lecam at gmail dot com @ 2011-04-27 23:41 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795
Summary: -Warray-bounds false positive
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: niko.lecam@gmail.com
$ gcc -v
Utilisation des specs internes.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.6.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configuré avec: /build/src/gcc-4.6-20110415/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --enable-gnu-unique-object
--enable-linker-build-id --with-ppl --enable-cloog-backend=isl --enable-lto
--enable-gold --enable-ld=default --enable-plugin --with-plugin-ld=ld.gold
--enable-multilib --disable-libstdcxx-pch --enable-checking=release
Modèle de thread: posix
gcc version 4.6.0 20110415 (prerelease) (GCC)
$ cat t.c
/* testcase (derived from wine) */
typedef struct
{
int len;
char data[1];
} rec;
int
p(rec *r, int len);
int
f (char prm1, char prm2)
{
char buf[10];
rec *r1 = (rec *)&buf;
r1->len = 10;
r1->data[0] = prm1;
r1->data[1] = prm2;
return p(r1, r1->len);
}
$ gcc -S -O2 -Wall t.c -save-temps
t.c: In function ‘f’:
t.c:19:11: attention : array subscript is above array bounds [-Warray-bounds]
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/48795] -Warray-bounds false positive 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com @ 2011-04-27 23:43 ` niko.lecam at gmail dot com 2011-05-01 7:29 ` d.g.gorbachev at gmail dot com ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: niko.lecam at gmail dot com @ 2011-04-27 23:43 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795 --- Comment #1 from Nicolas Le Cam <niko.lecam at gmail dot com> 2011-04-27 23:42:35 UTC --- Removing the call to p avoid the warning. Also tested by replacing p with a call to memcpy for example, which also triggers the warning. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/48795] -Warray-bounds false positive 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com 2011-04-27 23:43 ` [Bug tree-optimization/48795] " niko.lecam at gmail dot com @ 2011-05-01 7:29 ` d.g.gorbachev at gmail dot com 2011-05-01 10:27 ` niko.lecam at gmail dot com ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: d.g.gorbachev at gmail dot com @ 2011-05-01 7:29 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795 --- Comment #2 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2011-05-01 06:33:06 UTC --- "r1->data[1] = prm2" goes above "char data[1]" bounds. How it's a false positive? ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/48795] -Warray-bounds false positive 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com 2011-04-27 23:43 ` [Bug tree-optimization/48795] " niko.lecam at gmail dot com 2011-05-01 7:29 ` d.g.gorbachev at gmail dot com @ 2011-05-01 10:27 ` niko.lecam at gmail dot com 2011-07-23 22:57 ` pinskia at gcc dot gnu.org 2011-07-24 21:04 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: niko.lecam at gmail dot com @ 2011-05-01 10:27 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795 --- Comment #3 from Nicolas Le Cam <niko.lecam at gmail dot com> 2011-05-01 10:11:47 UTC --- (In reply to comment #2) > "r1->data[1] = prm2" goes above "char data[1]" bounds. How it's a false > positive? Because the structure is a kind of flexible array (code has to follow C89/C90 standard) and is big enough to handle a second member. (Or the warning has to be emitted even if you remove the call to p, which is not the case actually) This example is a deliberate use of overflow to circumvent the absence of flexible arrays in C89/C90, disabling Warray-bounds to avoid the flood it generates isn't the right solution IMHO. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/48795] -Warray-bounds false positive 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com ` (2 preceding siblings ...) 2011-05-01 10:27 ` niko.lecam at gmail dot com @ 2011-07-23 22:57 ` pinskia at gcc dot gnu.org 2011-07-24 21:04 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: pinskia at gcc dot gnu.org @ 2011-07-23 22:57 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-07-23 22:57:42 UTC --- Note you are also violating two things really, aliasing rules and alignment rules of C/C++. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/48795] -Warray-bounds false positive 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com ` (3 preceding siblings ...) 2011-07-23 22:57 ` pinskia at gcc dot gnu.org @ 2011-07-24 21:04 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: pinskia at gcc dot gnu.org @ 2011-07-24 21:04 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48795 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2011.07.24 21:04:04 Ever Confirmed|0 |1 --- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-07-24 21:04:04 UTC --- Confirmed. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-07-24 21:04 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2011-04-27 23:41 [Bug tree-optimization/48795] New: -Warray-bounds false positive niko.lecam at gmail dot com 2011-04-27 23:43 ` [Bug tree-optimization/48795] " niko.lecam at gmail dot com 2011-05-01 7:29 ` d.g.gorbachev at gmail dot com 2011-05-01 10:27 ` niko.lecam at gmail dot com 2011-07-23 22:57 ` pinskia at gcc dot gnu.org 2011-07-24 21:04 ` pinskia at gcc dot gnu.org
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).