pass on alternative g++ version to CMake settings?

[amwink]

For compiling a CMake project on a system that has /usr/bin/g++-7 as its default compiler, I am using the alternative /usr/bin/g++-9 to be able to use the std::filesystem functions (-std=g++-2a). The command g++-9 -std=gnu++-2a exits as expected -- the standard option is recognised.

In the Settings -> Build Settings I am using {C++ Compiler, /usr/bin/g++-9}, {C Compiler, /usr/bin/gcc-9}, {Linker, /usr/bin/g++-9}, {Shared Object Linker, /usr/bin/g++-9 -shared -fPIC}, {Archive, /usr/bin/gcc-ar-9 rcu}. The assembler, make and gdb commands do not have specific versions.

Then after 'Run Cmake' and 'Build', the output pane shows:

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...
/usr/bin/c++  [ ... many options and files ... ] -std=gnu++2a [ ... more options and files ]
c++: error: unrecognized command line option '-std=gnu++2a'; did you mean '-std=gnu++03'?
c++: error: unrecognized command line option '-std=gnu++2a'; did you mean '-std=gnu++03'?
...

The CMakeOutput.log file is full of calls to

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/usr/bin/cc

and in the project's CMakeCache.txt it says:

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...
CMakeCache.txt:CMAKE_CXX_COMPILER:FILEPATH=/usr/bin/c++
CMakeCache.txt:CMAKE_CXX_COMPILER_AR:FILEPATH=/usr/bin/gcc-ar-7
CMakeCache.txt:CMAKE_CXX_COMPILER_RANLIB:FILEPATH=/usr/bin/gcc-ranlib-7
CMakeCache.txt:CMAKE_C_COMPILER:FILEPATH=/usr/bin/cc
CMakeCache.txt:CMAKE_C_COMPILER_AR:FILEPATH=/usr/bin/gcc-ar-7
CMakeCache.txt:CMAKE_C_COMPILER_RANLIB:FILEPATH=/usr/bin/gcc-ranlib-7
...

This happens again if I delete all those files and re-run CMake. So it not only doesn't select the version of g++ (cc?) specified in the Build Settings, but also does explicitly select a different version than specified in the Build Settings.

Isn't that odd? And is it possible to control these CMake settings via the plugin in CodeLite?

[amwink]

One thing I tried, which I was sure would work, was to create a directory ~/.codelite/gcc with the links:

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$ ls -l1 ~/.codelite/gcc | awk '{print $9,$10,$11}' | grep u
ar -> /usr/bin/gcc-ar-9
as -> /usr/bin/as
g++ -> /usr/bin/g++-9
gcc -> /usr/bin/gcc-9
gdb -> /usr/bin/gdb
make -> /usr/bin/make

and put those in the Build Settings, but the CMake setup still uses programs from /usr/bin.

[DavidGH]

Hi,

(Warning: cmake isn't one of my favourite things and, apart from building CodeLite itself, I've little experience of using it.)

According to the cmake wiki there are various ways to specify which compiler to use. I suggest you try one of them, in either your project settings or CMakeLists.txt as appropriate.

Regards,

David

[amwink]

That's a clear answer, thanks! The reason that I hoped the settings for CMake would come from outside of the project's settings is to not have to change project settings when moving from 1 machine to another -- In CodeLite they're not in the project settings either.

But fully agree that CMake has loads of peculiarities, it's hard to cater for. It looks like the CMake -D route is the only one worth trying.