conan doesn't recieve CC/CXX variables from CLion

[kees-jan]

Testcase:

• In CLion, define a profile with an alternative compiler (for me, it's clang-10)
• Clear the conan cache
• Have CLion regenerate the project

Expected result

• This should complete without errors, and allow the project to be built
  • All conan packages should be build

Actual result

• CLion calls something along the lines of
  /home/kees-jan/opt/clion-2019.3.5/bin/cmake/linux/bin/cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=/usr/bin/clang-10 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-10 -G "CodeBlocks - Unix Makefiles" /home/kees-jan/src/cpp_starter_project
• This triggers conan to build the dependencies
• That fails (among others in docopt) with

CMake Error at conanbuildinfo.cmake:553 (message):
  Incorrect 'clang', is not the one detected by CMake: 'GNU'
Call Stack (most recent call first):
  conanbuildinfo.cmake:136 (conan_check_compiler)
  CMakeLists.txt:5 (CONAN_BASIC_SETUP)

Analysis

• Conan expects the CC and CXX variables to be set, in addition to the compiler settings, and they are not.
• I'm not sure whether to blame CLion, CMake, Conan, or this starter project for that shortcoming

[ddalcino]

Can you build the project from the command line? That would be an easy way to rule out clion as the culprit.

[kees-jan]

I'm surprised to say that yes, I can. Running the command-line quoted above succeeds without problems.

So now I'm speculating that CLion somehow messes up the environment and in that way triggers the failure? Odd...

[kees-jan]

I'm surprised to say that yes, I can. Running the command-line quoted above succeeds without problems.

So now I'm speculating that CLion somehow messes up the environment and in that way triggers the failure? Odd...

And indeed, to trigger the failure I'm observing from the commandline, I have to execute

CC=cc CXX=c++ /home/kees-jan/opt/clion-2019.3.5/bin/cmake/linux/bin/cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=/usr/bin/clang-10 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-10 -G "CodeBlocks - Unix Makefiles" /home/kees-jan/src/cpp_starter_project

I.e. set CXX and CMAKE_CXX_COMPILER to conflicting values

[ddalcino]

Ok, then we know for certain that CLion is the problem, and not this project or conan.

You will need to set up a new toolchain and a new cmake profile. To do that, you go to:
'File > Settings > Build, Execution, Deployment > Toolchains'
'File > Settings > Build, Execution, Deployment > CMake'

The documentation you want should be here: https://www.jetbrains.com/help/clion/how-to-switch-compilers-in-clion.html. This page should be able to help you a lot better than I can.

[kees-jan]

I have now been able to reproduce the problem from the commandline

Preparation:

cd cpp_starter_project
mkdir build
cd build/
cmake -DCMAKE_C_COMPILER=/usr/bin/clang-10 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-10 ..

Trigger the problem:

conan remove -f '*'
cmake -DCMAKE_C_COMPILER=/usr/bin/clang-10 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-10 ..

The final cmake invocation fails with nonzero exit status, because conan detects GCC instead of clang.

Instead of that final cmake invocation, you might also call make. That too makes conan attempt to build its packages, and fails with the same error.

[ddalcino]

According to conan-io/conan#1211, conan runs the compiler specified by the CC and CXX environment variables, not the cmake variables CMAKE_C_COMPILER and CMAKE_CXX_COMPILER. That thread suggests using conan profiles to set these variables, but that requires some modifications to cmake/Conan.cmake (see #32 if you want to do this).

I think it's easier to just set CC and CXX via command line. Try this:

rm -rf build/
mkdir build && cd build
CC=clang CXX=clang++ cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ..
cmake --build .          # Conan targets were already built using clang
conan remove -f '*'
cmake --build .          # Builds conan targets using system default --> failure
CC=clang CXX=clang++ cmake --build .   # Builds conan targets using clang --> success

If this works, you will need to convince CLion to inject those environment variables into the build command. The documentation linked in my last post explains how to do that.

[LtdSauce]

I got it to work applying the fix from #122 to the conan_cmake_install-call:

diff --git a/cmake/Conan.cmake b/cmake/Conan.cmake
index b57566f..44d1968 100644
--- a/cmake/Conan.cmake
+++ b/cmake/Conan.cmake
@@ -54,7 +54,10 @@ macro(run_conan)
       cpp_starter_use_imgui=${CPP_STARTER_USE_IMGUI}
       cpp_starter_use_sdl=${CPP_STARTER_USE_SDL}
       SETTINGS
-      ${settings})
+      ${settings}
+      ENV
+      CC=${CMAKE_C_COMPILER}
+      CXX=${CMAKE_CXX_COMPILER})
   endforeach()
 
 endmacro()

But i am not convenient enough about this to say that it is good and the right way to do it.

[aminya]

This is fixed in ProjectOptions v0.11.2
https://github.com/aminya/ProjectOptions