MantisBT - CMake
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IDProjectCategoryView StatusDate SubmittedLast Update
0007590CMakeModulespublic2008-09-02 07:212016-06-10 14:30
ReporterMahendra Ladhe 
Assigned ToKitware Robot 
PrioritynormalSeverityminorReproducibilityalways
StatusclosedResolutionmoved 
PlatformOSOS Version
Product VersionCMake-2-6 
Target VersionFixed in Version 
Summary0007590: CHECK_C_COMPILER_FLAG macro not working for gcc's -fprofile-arcs flag
DescriptionHi,
  shown below is part of my CMakeLists.txt file.

#To build the code for use with gcov, call cmake as below
#cmake -DGCOV=1 ..
IF (${GCOV})
    CHECK_C_COMPILER_FLAG (-fprofile-arcs FLAG_Gcov1)
    IF (FLAG_Gcov1)
      add_definitions (-fprofile-arcs)
    ELSE (FLAG_Gcov1)
      MESSAGE(FATAL_ERROR "Compiler does not support the -fprofile-arcs flag needed for using gcov")
    ENDIF (FLAG_Gcov1)
    CHECK_C_COMPILER_FLAG (-ftest-coverage FLAG_Gcov2)
    IF (FLAG_Gcov2)
      add_definitions (-ftest-coverage)
    ELSE (FLAG_Gcov2)
      MESSAGE(FATAL_ERROR "Compiler does not support the -ftest-coverage flag needed for using gcov")
    ENDIF (FLAG_Gcov2)
ENDIF (${GCOV})

I want to give user an option to compile the code for use with GCOV:
the GNU code coverage tool. For this the code needs to be compiled with
-fprofile-arcs and -ftest-coverage flags.

    When I invoke cmake as follows
cmake -DGCOV=1 ..
I get the following error
CMake Error: Compiler does not support the -fprofile-arcs flag needed
for using gcov

    Well, the gcc compiler on my Linux box does support -fprofile-arcs
compilation flag.
The CMakeFiles/CMakeError.log shows the cause of error.

=========================================================================================
Performing C SOURCE FILE Test FLAG_Gcov1 failed with the following output:
/usr/bin/gmake -f CMakeFiles/cmTryCompileExec.dir/build.make CMakeFiles/cmTryCompileExec.dir/build
gmake[1]: Entering directory `/proj/magnum/mladhe/p4/L7/bld_x86/CMakeFiles/CMakeTmp'
/home/srgorti/freeware/usr/bin/cmake -E cmake_progress_report /proj/magnum/mladhe/p4/L7/bld_x86/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec.dir/src.o
/usr/local/bin/gcc -DFLAG_Gcov1 -fprofile-arcs -o CMakeFiles/cmTryCompileExec.dir/src.o -c /proj/magnum/mladhe/p4/L7/bld_x86/CMakeFiles/CMakeTmp/src.c
Linking C executable cmTryCompileExec
/home/srgorti/freeware/usr/bin/cmake -P CMakeFiles/cmTryCompileExec.dir/cmake_clean_target.cmake
/usr/local/bin/gcc -DFLAG_Gcov1 -fPIC "CMakeFiles/cmTryCompileExec.dir/src.o" -o cmTryCompileExec -rdynamic
CMakeFiles/cmTryCompileExec.dir/src.o(.text+0x43): In function `global constructors keyed to 0_main':
: undefined reference to `__gcov_init'
CMakeFiles/cmTryCompileExec.dir/src.o(.data+0x24): undefined reference to `__gcov_merge_add'
collect2: ld returned 1 exit status
gmake[1]: *** [cmTryCompileExec] Error 1
gmake[1]: Leaving directory `/proj/magnum/mladhe/p4/L7/bld_x86/CMakeFiles/CMakeTmp'
gmake: *** [cmTryCompileExec/fast] Error 2

Source file was:
int main() { return 0;}
=========================================================================================

So the reason is when source file is compiled with -fprofile-arcs,
the cmake does not supply the same flag while linking which the gcc needs
as the object module has certain gcov related code like functions gcov_init,
gcov_merge_add etc.

So the working of Check_C_Compiler_Flag macro needs enhancement to
detect support for such kinds of compiler flags.
Steps To Reproduce
Additional Information
TagsNo tags attached.
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Attached Files
Issue History
Date ModifiedUsernameFieldChange
2008-09-02 07:21Mahendra LadheNew Issue
2008-09-03 15:00Bill HoffmanNote Added: 0013280
2008-09-03 15:00Bill HoffmanStatusnew => assigned
2008-09-03 15:00Bill HoffmanAssigned To => Bill Hoffman
2008-09-04 00:04Mahendra LadheNote Added: 0013292
2008-09-09 14:12Bill HoffmanNote Added: 0013384
2008-09-09 14:14Bill HoffmanNote Added: 0013385
2008-09-11 04:24Mahendra LadheNote Added: 0013406
2008-09-11 08:50Bill HoffmanNote Added: 0013411
2008-09-15 23:10Mahendra LadheNote Added: 0013478
2008-10-01 10:17Bill HoffmanNote Added: 0013639
2008-10-01 10:18Bill HoffmanAssigned ToBill Hoffman => Alex Neundorf
2010-08-29 10:23Kovarththanan RajaratnamCategoryCMake => Modules
2012-01-04 16:12Alex NeundorfNote Added: 0028177
2012-01-04 16:12Alex NeundorfAssigned ToAlex Neundorf =>
2012-01-04 16:12Alex NeundorfStatusassigned => backlog
2016-06-10 14:27Kitware RobotNote Added: 0041446
2016-06-10 14:27Kitware RobotStatusbacklog => resolved
2016-06-10 14:27Kitware RobotResolutionopen => moved
2016-06-10 14:27Kitware RobotAssigned To => Kitware Robot
2016-06-10 14:30Kitware RobotStatusresolved => closed

Notes
(0013280)
Bill Hoffman   
2008-09-03 15:00   
You could try this:

SET(CMAKE_REQUIRED_LIBRARIES -fprofile-arcs )
CHECK_C_COMPILER_FLAG (-fprofile-arcs FLAG_Gcov1)
(0013292)
Mahendra Ladhe   
2008-09-04 00:04   
Per Bill's suggestion, when I added one more line
SET(CMAKE_REQUIRED_LIBRARIES -fprofile-arcs )
found that gcc is no longer being passed the flag -fprofile-arcs
during compilation, but only during linking so it has no effect.
i.e. after incorporating the suggestion, my CMakeLists.txt's relevant
portion became as below.

#To build the code for use with gcov, call cmake as below
#cmake -DGCOV=1 ..
IF (${GCOV})
    SET(CMAKE_REQUIRED_LIBRARIES -fprofile-arcs )
    CHECK_C_COMPILER_FLAG (-fprofile-arcs FLAG_Gcov1)
    IF (FLAG_Gcov1)
      add_definitions (-fprofile-arcs)
    ELSE (FLAG_Gcov1)
      MESSAGE(FATAL_ERROR "Compiler does not support the -fprofile-arcs flag needed for using gcov")
    ENDIF (FLAG_Gcov1)
    CHECK_C_COMPILER_FLAG (-ftest-coverage FLAG_Gcov2)
    IF (FLAG_Gcov2)
      add_definitions (-ftest-coverage)
    ELSE (FLAG_Gcov2)
      MESSAGE(FATAL_ERROR "Compiler does not support the -ftest-coverage flag needed for using gcov")
    ENDIF (FLAG_Gcov2)
ENDIF (${GCOV})

After this change I'm not getting the error message
"Compiler does not support the -fprofile-arcs flag needed for using gcov"
But the statement add_definitions (-fprofile-arcs) is not taking effect.
During compilation(e.g. gcc -c a.c -o a.o), gcc is not being passed -fprofile-arcs flag. So code does not get compiled for use with GCOV.

One more observation: While the cmake 2.6 documentation for CHECK_C_SOURCE_COMPILES is as follows.
=======================
CHECK_C_SOURCE_COMPILES(SOURCE VAR)

  SOURCE - source code to try to compile
  VAR - variable to store whether the source code compiled

The following variables may be set before calling this macro to modify the way the check is run:

  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
=======================

the documentation for CHECK_C_COMPILER_FLAG macro does not say that
the variable CMAKE_REQUIRED_LIBRARIES may be set before calling this
macro to modify the way the check is run.
(0013384)
Bill Hoffman   
2008-09-09 14:12   
I have updated the docs to say this:
 
 CheckCCompilerFlag
       Check whether the C compiler supports a given flag.

       CHECK_C_COMPILER_FLAG(FLAG VARIABLE)

         FLAG - the compiler flag
         VARIABLE - variable to store the result

       

         This actually calls the check_c_source_compiles macro.
         See help for CheckCSourceCompiles for a listing of variables
         that can modify the build.



       Defined in: C:/hoffman/My Builds/CMake/Modules/CheckCCompilerFlag.cmake

  CheckCSourceCompiles
       macro which checks if the source code compiles

       CHECK_C_SOURCE_COMPILES(SOURCE VAR)

         SOURCE - source code to try to compile
         VAR - variable to store whether the source code compiled

       

       The following variables may be set before calling this macro to modify
       the way the check is run:

         CMAKE_REQUIRED_FLAGS = string of compile command line flags
         CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
         CMAKE_REQUIRED_INCLUDES = list of include directories
         CMAKE_REQUIRED_LIBRARIES = list of libraries to link



       Defined in: C:/hoffman/My Builds/CMake/Modules/CheckCSourceCompiles.cmake
(0013385)
Bill Hoffman   
2008-09-09 14:14   
Does the add_definition work without the if?

Also, it might be better to modify CMAKE_CXX_FLAGS instead.

Something like this should work:
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fprofile-arcs")

Make sure this is done BEFORE the target that you want to build with profile information.
(0013406)
Mahendra Ladhe   
2008-09-11 04:24   
Yes, add_definitions work without the if, but only while compiling.
Consider my following simple CMakeLists.txt file

add_definitions (-fprofile-arcs)
add_definitions (-ftest-coverage)
add_executable(sample_test test.c)

When compiling test.c gcc did receive -fprofile-arcs and -ftest-coverage
flags. But when linking it didn't. So linking failed as gcc needs the
two flags again so that it can link gcov library.

Adding following line instead of 2 add_definitions is helping and giving
the desired behaviour.
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fprofile-arcs -ftest-coverage")

Now gcc is being passed these 2 flags while compiling and as well as linking.

Thanks Bill.

But the behaviour of Check_C_Compiler_Flag macro still needs a fix.
(0013411)
Bill Hoffman   
2008-09-11 08:50   
I am not sure, you are confusing link flags and compile flags. In this case you want to test a link flag and a compile flag at the same time. They happen to be the same thing. However, many compile flags are not useful or wanted at link time. add_definition is only used at compile time and is really meant for -D stuff.
(0013478)
Mahendra Ladhe   
2008-09-15 23:10   
Yes, -fprofile-arcs and -ftest-coverage are both compile and link flags.
So is there any way to check if such flags(compile+link) are supported by
the compiler?
(0013639)
Bill Hoffman   
2008-10-01 10:17   
You could do something like this:

set(CMAKE_C_FLAGS_SAVE "${CMAKE_C_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fprofile-arcs")
CHECK_C_COMPILER_FLAG (-fprofile-arcs FLAG_Gcov1)

But that seems kind of silly. I guess the macro could be augmented to support compile and link flags. Maybe a version that just sets CMAKE_C_FLAGS.
(0028177)
Alex Neundorf   
2012-01-04 16:12   
I think I won't work on this.

Alex
(0041446)
Kitware Robot   
2016-06-10 14:27   
Resolving issue as `moved`.

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