public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug target/58320] New: [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0
@ 2013-09-05 10:06 doko at gcc dot gnu.org
2013-09-05 10:36 ` [Bug target/58320] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: doko at gcc dot gnu.org @ 2013-09-05 10:06 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58320
Bug ID: 58320
Summary: [4.7 / 4.8 / 4.9 Regression] code used in autoconf
test fails with -O2, works with -O0
Product: gcc
Version: 4.7.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: doko at gcc dot gnu.org
seen on arm-linux-gnueabihf, as part of an autoconf test in librep:
$ cat stack.c
#include <stdlib.h>
void inner (char *foo) {
char bar;
exit (!(foo >= &bar));
}
void main () {
char foo;
inner (&foo);
}
$ gcc-4.6 -o conftest -O2 stack.c && ./conftest ; echo $?
0
$ gcc-4.7 -o conftest -O2 stack.c && ./conftest ; echo $?
1
$ gcc-4.8 -o conftest -O2 stack.c && ./conftest ; echo $?
1
$ gcc-4.8 -o conftest -O0 stack.c && ./conftest ; echo $?
0
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/58320] [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0
2013-09-05 10:06 [Bug target/58320] New: [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0 doko at gcc dot gnu.org
@ 2013-09-05 10:36 ` rguenth at gcc dot gnu.org
2013-09-05 12:12 ` schwab@linux-m68k.org
2013-09-05 13:01 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-09-05 10:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58320
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Well, it's clearly a bogus test - you are comparing addresses of two distinct
objects which invokes undefined behavior.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/58320] [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0
2013-09-05 10:06 [Bug target/58320] New: [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0 doko at gcc dot gnu.org
2013-09-05 10:36 ` [Bug target/58320] " rguenth at gcc dot gnu.org
@ 2013-09-05 12:12 ` schwab@linux-m68k.org
2013-09-05 13:01 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: schwab@linux-m68k.org @ 2013-09-05 12:12 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58320
--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
Casting to uintptr_t should probably make this work as intented.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/58320] [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0
2013-09-05 10:06 [Bug target/58320] New: [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0 doko at gcc dot gnu.org
2013-09-05 10:36 ` [Bug target/58320] " rguenth at gcc dot gnu.org
2013-09-05 12:12 ` schwab@linux-m68k.org
@ 2013-09-05 13:01 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-09-05 13:01 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58320
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Well, until the compiler comes along and inlines 'inner'.
This is really a GIGO test.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-09-05 13:01 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-09-05 10:06 [Bug target/58320] New: [4.7 / 4.8 / 4.9 Regression] code used in autoconf test fails with -O2, works with -O0 doko at gcc dot gnu.org
2013-09-05 10:36 ` [Bug target/58320] " rguenth at gcc dot gnu.org
2013-09-05 12:12 ` schwab@linux-m68k.org
2013-09-05 13:01 ` rguenth 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).