Question

Is there a safe, portable way to determine (during compile time) the endianness of the platform that my program is being compiled on? I’m writing in C.

[EDIT]
Thanks for the answers, I decided to stick with the runtime solution!

Answer 1

This is for compile time checking

You could use information from the boost header file endian.hpp, which covers many platforms.

edit for runtime checking

bool isLittleEndian()
{
    short int number = 0x1;
    char *numPtr = (char*)&number;
    return (numPtr[0] == 1);
}

Create an integer, and read its first byte (least significant byte). If that byte is 1, then the system is little endian, otherwise it’s big endian.

edit Thinking about it

Yes you could run into a potential issue in some platforms (can’t think of any) where sizeof(char) == sizeof(short int). You could use fixed width multi-byte integral types available in <stdint.h>, or if your platform doesn’t have it, again you could adapt a boost header for your use: stdint.hpp