What happens for C/C++ builds if CMAKE_BUILD_TYPE is empty?

Question

When the variable CMAKE_BUILD_TYPE is empty which compiler flags are used? Does the compiler then simply use CMAKE_CXX_FLAGS and CMAKE_C_FLAG

Answer 1

The default will be "empty" or "Debug" depending on the compiler. The value of the variable will be only of interest in places where SOME_VAR_${CONFIG} is used. So to answer your question. From my understanding the debug flags could be added. The documentation (http://www.cmake.org/cmake/help/v3.3/variable/CMAKE_BUILD_TYPE.html) is unfortunately not so clear.

Answer 2

As a comment on https://blog.kitware.com/cmake-and-the-default-build-type/ says, the default (empty) build type is targeted at Linux distributions which want to use the same compiler flags for multiple packages.