MantisBT - CMake
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IDProjectCategoryView StatusDate SubmittedLast Update
0013955CMake(No Category)public2013-02-27 03:392016-06-10 14:31
ReporterMathieu Malaterre 
Assigned ToBill Hoffman 
PrioritynormalSeverityminorReproducibilityhave not tried
StatusclosedResolutionmoved 
PlatformOSOS Version
Product Version 
Target VersionFixed in Version 
Summary0013955: warning: assuming signed overflow does not occur when simplifying conditional to constant
DescriptionCmake generates code which confuses gcc optimizer:


/home/mathieu/Perso/gdcm-gcc/Testing/Source/Common/Cxx/gdcmCommonTests.cxx: In function ‘int main(int, char**)’:
/home/mathieu/Perso/gdcm-gcc/Testing/Source/Common/Cxx/gdcmCommonTests.cxx:218: warning: assuming signed overflow does not occur when simplifying conditional to constant [-Wstrict-overflow]

Code generated by cmake is:

...
  /* If partial match is requested. */
  if(testToRun == -1 && ac > 1)
    {
    partial_match = (strcmp(av[1], "-R") == 0) ? 1 : 0;
    }
...


Looks like gcc thinks ac can be negative...
Steps To Reproduce
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Issue History
Date ModifiedUsernameFieldChange
2013-02-27 03:39Mathieu MalaterreNew Issue
2013-02-27 03:43Mathieu MalaterreNote Added: 0032391
2013-02-27 08:29Brad KingNote Added: 0032392
2013-02-27 08:29Brad KingAssigned To => Bill Hoffman
2013-02-27 08:29Brad KingStatusnew => assigned
2013-02-27 08:42Mathieu MalaterreNote Added: 0032393
2016-06-10 14:28Kitware RobotNote Added: 0042238
2016-06-10 14:28Kitware RobotStatusassigned => resolved
2016-06-10 14:28Kitware RobotResolutionopen => moved
2016-06-10 14:31Kitware RobotStatusresolved => closed

Notes
(0032391)
Mathieu Malaterre   
2013-02-27 03:43   
Compilation option is:

CXXFLAGS=-O2 -Wstrict-overflow
(0032392)
Brad King   
2013-02-27 08:29   
I can reproduce this with g++ < 4.6 using -O3 -Wstrict-overflow, but not with -O2 or with g++ >= 4.6.

The problem is here:

 http://cmake.org/gitweb?p=cmake.git;a=blob;f=Templates/TestDriver.cxx.in;hb=v2.8.10.2#l72 [^]

in code of the form:

 if(ac < 2)
   {
   ...
   --ac;
   ...
   }

From that gcc concludes it is possible for ac to be negative.
(0032393)
Mathieu Malaterre   
2013-02-27 08:42   
Setup on my side is debian/sid:

$ /usr/bin/c++ --version
c++ (Debian 4.7.2-18) 4.7.2
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cd /home/mathieu/Perso/gdcm-schroot/Testing/Source/MessageExchangeDefinition/Cxx && /usr/bin/c++ -Wstrict-overflow -O2 -I/home/mathieu/Perso/gdcm-schroot/Source/Common -I/home/mathieu/Perso/gdcm/Source/Common -I/home/mathieu/Perso/gdcm/Testing/Source/Data -I/home/mathieu/Perso/gdcm-schroot/Testing/Source/Data -I/home/mathieu/Perso/gdcm/Source/DataStructureAndEncodingDefinition -I/home/mathieu/Perso/gdcm/Source/DataDictionary -I/home/mathieu/Perso/gdcm/Source/MediaStorageAndFileFormat -I/home/mathieu/Perso/gdcm/Source/MessageExchangeDefinition -o CMakeFiles/gdcmMEXDTests.dir/gdcmMEXDTests.cxx.o -c /home/mathieu/Perso/gdcm-schroot/Testing/Source/MessageExchangeDefinition/Cxx/gdcmMEXDTests.cxx
/home/mathieu/Perso/gdcm-schroot/Testing/Source/MessageExchangeDefinition/Cxx/gdcmMEXDTests.cxx: In function 'int main(int, char**)':
/home/mathieu/Perso/gdcm-schroot/Testing/Source/MessageExchangeDefinition/Cxx/gdcmMEXDTests.cxx:147:3: warning: assuming signed overflow does not occur when simplifying conditional to constant [-Wstrict-overflow]
(0042238)
Kitware Robot   
2016-06-10 14:28   
Resolving issue as `moved`.

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