Installation directory in CMakeLists.txt, suitable for Visual Studio and Qt Creator

Question

I have to deal with CMake 3.x, Qt Creator 3.3.0, Qt 4.8.6, Visual Studio 2008 in Windows (and rarely Qt Creator + GCC in Debian).

This instruction

install(TARGETS ${PROJECT} DESTINATION ${CMAKE_INSTALL_PREFIX}/lib)

is not comfortable because of mixing debug and release *.lib files in the same directory. I'd like to save libs in the corresponding subfolder.

I've tried the following instruction from here:

install(TARGETS ${PROJECT} DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/\${BUILD_TYPE})

It works fine for Visual Studio, as it is a multi-configuration solution and we pass ${BUILD_TYPE}, protected by backslash '\' for further propagation. But how can I achieve the same output for Qt Creator + MS C++ compiler? Should I assign Debug(for example) to ${CMAKE_BUILD_TYPE} (via command-line interface) and special custom flag, which tells CMake that we deal with nmake/make? I mean conditional install instruction which will work fine in Windows and Linux and require minimal differences in the command-line arguments for CMake. I don't want to reinvent the wheel if there is a standard solution.

Answer 1

You saw that you can use BUILD_TYPE variable set at compile time to configure the target folder of your library at installation. This is specific to Visual Studio.

In other build systems (make, nmake, ninja, etc.) you have to use CMAKE_BUILD_TYPE variable, set at configuration time to retrieve the same information. In such case, as you felt, different configurations (Debug and Release) have to be generated in separated build folders. In these folders, CMake generation step is done with the right value in CMAKE_BUILD_TYPE variable. Example:

cd /home/user/project/xx_project/build_release
cmake -DCMAKE_BUILD_TYPE=Release /home/user/project/xx_project/src
cd /home/user/project/xx_project/build_debug
cmake -DCMAKE_BUILD_TYPE=Debug /home/user/project/xx_project/src

To detect if the user is building from Visual Studio or from command line, "there is a variable for that": The MSVC_IDE Cmake variable

A solution can be something like

if(MSVC_IDE)
  install(TARGETS ${PROJECT} DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/\${BUILD_TYPE})
else()
  install(TARGETS ${PROJECT} DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/${CMAKE_BUILD_TYPE})
endif()

I am not completely sure of the necessity of the backslash before ${CMAKE_BUILD_TYPE}. You should test that by yourself