 CFLAGS enables the addition of switches for the C compiler, while CXXFLAGS is meant to be used when invoking a C++ compiler.Similarly, a variable CPPFLAGS exists with switches to be passed to the C or C++ preprocessor.These variables are most commonly used to specify optimization or debugging switches to a compiler, as for example codice_1, codice_2 or (GCC-specific) codice_3.