Change default value of CMAKE_CXX_FLAGS_DEBUG and friends in CMake

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I just wanted to add the four possibilities I see:

  1. Having your own toolchain files containing the presets for each compiler you support like:

    GNUToolchain.cmake

     set(CMAKE_CXX_FLAGS_DEBUG "-ggdb3 -O0" CACHE STRING "")

    And then use it with

     cmake -DCMAKE_TOOLCHAIN_FILE:string=GNUToolchain.cmake ...

  2. You can try to determine the compiler by checking CMAKE_GENERATOR (which is valid before the project() command):

    CMakeLists.txt

     if("${CMAKE_GENERATOR}" MATCHES "Makefiles" OR 
    ("${CMAKE_GENERATOR}" MATCHES "Ninja" AND NOT WIN32))
     set(CMAKE_CXX_FLAGS_DEBUG "-ggdb3 -O0" CACHE STRING "")
 endif()

 project(your_project C CXX)

  3. You can use CMAKE_USER_MAKE_RULES_OVERRIDE to give a script with your own ..._INIT values:

    It is loaded after CMake’s builtin compiler and platform information modules have been loaded but before the information is used. The file may set platform information variables to override CMake’s defaults.

    MyInitFlags.cmake

     # Overwrite the init values choosen by CMake
 if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
     set(CMAKE_CXX_FLAGS_DEBUG_INIT "-ggdb3 -O0")
 endif()

    CMakeLists.txt

     set(CMAKE_USER_MAKE_RULES_OVERRIDE "MyInitFlags.cmake")

 project(your_project C CXX)

  4. You can simplify your solution from March 1st by checking against the ..._INIT variants of the compiler flag variables:

    CMakeLists.txt

     project(your_project C CXX)

 if (DEFINED CMAKE_CXX_FLAGS_DEBUG_INIT AND  
     "${CMAKE_CXX_FLAGS_DEBUG_INIT}" STREQUAL "${CMAKE_CXX_FLAGS_DEBUG}")
     # Overwrite the init values choosen by CMake
     if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
         set(CMAKE_CXX_FLAGS_DEBUG "-ggdb3 -O0" CACHE STRING "" FORCE)
     endif()
 endif()

Comments:

I prefer and use the toolchain variant. But I admit it has the disadvantage of having to give the toolchain file manually (if you are not calling cmake via a script/batch file).

References:

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