c++ - Debug vs Release in CMake

Question

In a GCC compiled project,

• How do I run CMake for each target type (debug/release)?
• How do I specify debug and release C/C++ flags using CMake?
• How do I express that the main executable will be compiled with g++ and one nested library with gcc?

Answer 1

With CMake, it's generally recommended to do an "out of source" build. Create your CMakeLists.txt in the root of your project. Then from the root of your project:

mkdir Release
cd Release
cmake -DCMAKE_BUILD_TYPE=Release ..
make

And for Debug (again from the root of your project):

mkdir Debug
cd Debug
cmake -DCMAKE_BUILD_TYPE=Debug ..
make

Release / Debug will add the appropriate flags for your compiler. There are also RelWithDebInfo and MinSizeRel build configurations.

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You can modify/add to the flags by specifying a toolchain file in which you can add CMAKE_<LANG>_FLAGS_<CONFIG>_INIT variables, e.g.:

set(CMAKE_CXX_FLAGS_DEBUG_INIT "-Wall")
set(CMAKE_CXX_FLAGS_RELEASE_INIT "-Wall")

See CMAKE_BUILD_TYPE for more details.

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As for your third question, I'm not sure what you are asking exactly. CMake should automatically detect and use the compiler appropriate for your different source files.