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From: "mikpe at it dot uu.se" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/50012] New: C++ front end misses -Wsign-compare warnings when extraneous parentheses are present
Date: Sun, 07 Aug 2011 11:22:00 -0000 [thread overview]
Message-ID: <bug-50012-4@http.gcc.gnu.org/bugzilla/> (raw)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50012
Summary: C++ front end misses -Wsign-compare warnings when
extraneous parentheses are present
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: mikpe@it.uu.se
In this test case two similar functions compare an unsigned int with a signed
int, differing only in whether the unsigned sub-expression has an extra pair of
parentheses around it or not. The C FE correctly issues a -Wsign-compare
diagnostic for both functions, but the C++ FE fails to do so for the function
with the extra parentheses.
> cat bug.c
int foo(unsigned int *a, int b)
{
return (*a) <= b;
}
int bar(unsigned int *a, int b)
{
return *a <= b;
}
> gcc/xgcc -Bgcc/ -O2 -Wsign-compare -S bug.c
bug.c: In function 'foo':
bug.c:3:17: warning: comparison between signed and unsigned integer expressions
[-Wsign-compare]
bug.c: In function 'bar':
bug.c:8:15: warning: comparison between signed and unsigned integer expressions
[-Wsign-compare]
> gcc/g++ -Bgcc/ -O2 -Wsign-compare -S /tmp/bug.c
/tmp/bug.c: In function 'int bar(unsigned int*, int)':
/tmp/bug.c:8:18: warning: comparison between signed and unsigned integer
expressions [-Wsign-compare]
This difference exists in 4.7-20110806, 4.6.1, and 4.5.3, but not in 4.4.6.
The test case is derived from ipa-inline-analysis.c, specifically Jan Hubicka's
recent change in r177484. That change introduced a signed/unsigned comparison,
but due to this C++ FE bug and the recent "build stage2 etc with g++ by
default" change, the error went undetected. That is, until people started
using --disable-build-poststage1-with-cxx to reduce bootstrap times, where it
ultimately breaks bootstrap, see PR50005.
next reply other threads:[~2011-08-07 11:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-07 11:22 mikpe at it dot uu.se [this message]
2011-08-07 19:52 ` [Bug c++/50012] " mikpe at it dot uu.se
2011-08-08 10:09 ` [Bug c++/50012] [4.5/4.6/4.7 Regression] " rguenth at gcc dot gnu.org
2011-08-14 12:43 ` mikpe at it dot uu.se
2011-08-19 7:34 ` jakub at gcc dot gnu.org
2011-10-10 12:19 ` rguenth at gcc dot gnu.org
2011-12-19 15:00 ` jakub at gcc dot gnu.org
2012-01-05 17:43 ` jakub at gcc dot gnu.org
2012-01-07 1:32 ` ian at airs dot com
2012-01-14 0:26 ` ian at gcc dot gnu.org
2012-01-14 0:27 ` [Bug c++/50012] [4.5/4.6 " ian at airs dot com
2012-07-02 12:07 ` rguenth at gcc dot gnu.org
2012-11-13 11:24 ` [Bug c++/50012] [4.6 " paolo.carlini at oracle dot com
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