背景

为了更好的进行跨平台移植、编译、调试。

具体操作

宏操作

#ifdef _WIN32
   //define something for Windows (32-bit and 64-bit, this part is common)
   #ifdef _WIN64
      //define something for Windows (64-bit only)
   #else
      //define something for Windows (32-bit only)
   #endif
#elif __ANDROID__
    // do android something
#elif __linux__
    // do linux something
#elif __unix__ // all unices not caught above
    // do Unix something
#elif defined(_POSIX_VERSION)
    // do POSIX something
#else
   #error "Unknown compiler"
#endif

or 代码内操作

注意： 条件没有使能的编译内容，编译器不会对该内容进行错误检查。

#if defined(_WIN32)
    std::cout << "this is win32 compiler" << endl;
#elif defined(_WIN64)
    std::cout << "this is win64 compiler" << endl;
#elif defined(__linux__)
    std::cout << "this is linux compiler" << endl;
#elif defined(__unix__)
    std::cout << "this is unix compiler" << endl;
#elif defined(__ANDROID__)
    std::cout << "this is android compiler" << endl;
#endif