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* [Bug c/45884] New: Incorrect removal of check for "less than zero" after adding value to (signed) long
@ 2010-10-04 17:58 anders_jagd at yahoo dot com
2010-10-04 18:01 ` [Bug c/45884] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: anders_jagd at yahoo dot com @ 2010-10-04 17:58 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45884
Summary: Incorrect removal of check for "less than zero" after
adding value to (signed) long
Product: gcc
Version: 4.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: anders_jagd@yahoo.com
Created attachment 21959
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=21959
Source (test.c), Makefile, Binaries, test.i, gcc -dumpspecs etc. See README.txt
When compiled with -O2, the below (val < 0) check is, under some conditions
(see attachment), optimized away:
...
long val10, val;
char *s;
...
if((*s >= '0') && (*s <= '9')) {
val10 = val * 10; // Skip overflow check, not the issue we are showing
val = val10 + (*s - '0');
/****** OPTIMIZED AWAY IN CASE OF -O2 ******/
if(val < 0) {
/* Overflow */
return -1;
}
...
}
Build on ubuntu (2.6.32-25-generic)
gcc version 4.4.3-4ubuntu5
machine i486-linux-gnu
Attaching complete test case with:
Makefile
Source (test.c)
Binaries
Result from compiling with -save-temps (test.i)
System configuration, gcc -dumpspecs, etc.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/45884] Incorrect removal of check for "less than zero" after adding value to (signed) long
2010-10-04 17:58 [Bug c/45884] New: Incorrect removal of check for "less than zero" after adding value to (signed) long anders_jagd at yahoo dot com
@ 2010-10-04 18:01 ` pinskia at gcc dot gnu.org
2010-10-04 18:12 ` anders_jagd at yahoo dot com
2010-10-04 18:13 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2010-10-04 18:01 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45884
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-10-04 18:01:46 UTC ---
Signed integer overflow is undefined so what GCC is doing is correct. Use
-fwarpv if you want it to be defined to wrapping.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/45884] Incorrect removal of check for "less than zero" after adding value to (signed) long
2010-10-04 17:58 [Bug c/45884] New: Incorrect removal of check for "less than zero" after adding value to (signed) long anders_jagd at yahoo dot com
2010-10-04 18:01 ` [Bug c/45884] " pinskia at gcc dot gnu.org
@ 2010-10-04 18:12 ` anders_jagd at yahoo dot com
2010-10-04 18:13 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: anders_jagd at yahoo dot com @ 2010-10-04 18:12 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45884
--- Comment #2 from Anders Jagd <anders_jagd at yahoo dot com> 2010-10-04 18:12:16 UTC ---
(In reply to comment #1)
> Signed integer overflow is undefined so what GCC is doing is correct. Use
> -fwarpv if you want it to be defined to wrapping.
I acknowledge that ISO/IEC 9899 defines integer overflow to be undefined. What
GCC doing is thus "not incorrect". However, would this maybe be a bit too
aggressive optimization at -O2 ?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/45884] Incorrect removal of check for "less than zero" after adding value to (signed) long
2010-10-04 17:58 [Bug c/45884] New: Incorrect removal of check for "less than zero" after adding value to (signed) long anders_jagd at yahoo dot com
2010-10-04 18:01 ` [Bug c/45884] " pinskia at gcc dot gnu.org
2010-10-04 18:12 ` anders_jagd at yahoo dot com
@ 2010-10-04 18:13 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2010-10-04 18:13 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45884
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-10-04 18:13:15 UTC ---
See -fstrict-overflow too.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2010-10-04 17:58 [Bug c/45884] New: Incorrect removal of check for "less than zero" after adding value to (signed) long anders_jagd at yahoo dot com
2010-10-04 18:01 ` [Bug c/45884] " pinskia at gcc dot gnu.org
2010-10-04 18:12 ` anders_jagd at yahoo dot com
2010-10-04 18:13 ` pinskia at gcc dot gnu.org
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