msvc { contains(QMAKE_TARGET.arch, x86_64) { WORD_SIZE = 64 } else { WORD_SIZE = 32 } } win32-g++ { WIN_FIND = $$(SYSTEMROOT)\system32\find MINGW64 = $$system($$QMAKE_CXX -Q --help=target | $$WIN_FIND \"-m64\") contains(MINGW64,[enabled]) { WORD_SIZE = 64 } else { WORD_SIZE = 32 } } linux-g++ { GCC64 = $$system($$QMAKE_CXX -Q --help=target | grep m64) contains(GCC64,[enabled]) { WORD_SIZE = 64 } else { WORD_SIZE = 32 } } linux-g++-32 { WORD_SIZE = 32 } linux-g++-64 { WORD_SIZE = 64 } linux-clang { # Assume 64 bit until we find out how to detect the compiler architecture WORD_SIZE = 64 } macx-clang { # TODO WORD_SIZE = 64 }