# CXXFLAGS

This is a CMake Environment Variable. Its initial value is taken from the calling process environment.

Add default compilation flags to be used when compiling `CXX` (C++) files.

CMake uses this environment variable value, in combination with its own builtin default flags for the toolchain, to initialize and store the `CMAKE_CXX_FLAGS` cache entry. This occurs the first time a build tree is configured for language `CXX`. For any configuration run (including the first), the environment variable will be ignored if the `CMAKE_CXX_FLAGS` variable is already defined.

See also `CMAKE_CXX_FLAGS_INIT`.