#if defined(_MSC_VER)
    #define R_COMPILER_MSVC
    #define R_WINDOWS

    #ifdef _WIN64
        #define R_64BIT
    #else
        #define R_32BIT
    #endif

    #ifdef _DEBUG
        #define R_DEBUG
    #endif
#elif defined(__GNUC__)
    #define R_COMPILER_GCC

    #ifdef __CYGWIN__
        #define R_WINDOWS
    #endif
    #ifdef __linux__
        #define R_LINUX
        #define _GNU_SOURCE
    #endif
    #ifdef __APPLE__
        #define R_APPLE
    #endif

    #if __x86_64__ || __ppc64__
        #define R_64BIT
    #else
        #define R_32BIT
    #endif
#else
    #error "unsupported compiler"
#endif