How to query target architecture endianness during gcc compilation?-CodePudding

I would like to promote more of my endianness logic to compile time constexpr's. I know that in C 20, this is highly standardized via std::endian. However, for the moment I am targeting C 17.

How can I query the target architecture's endianness from within my C code? Prefer simple constexpr functions and macros to autoconf. Would appreciate working snippets for GCC, Clang, and MSVC.

CodePudding user response：

You can use preprocessor defined macros of GCC like below

#if __BYTE_ORDER == __BIG_ENDIAN

#if __BYTE_ORDER == __LITTLE_ENDIAN

You've to include #include <endian.h> header

CodePudding user response：

For a cross-platform solution you can use Boost.Predef which is a preprocessor header that even works with C. It contains various predefined macros for the target platform including the endianness (BOOST_ENDIAN_*)

#if BOOST_ENDIAN_BIG_BYTE
    std::cout << "Big endian!";
#elif BOOST_ENDIAN_LITTLE_BYTE
    std::cout << "Little endian!";
#endif