jandeboevrieBig-Endian Testing with QEMU
> When programming, it is still important to write code that runs correctly on systems with either byte order
What you should do instead is write all your code so it is little-endian only, as the only relevant big-endian architecture is s390x, and if someone wants to run your code on s390x, they can afford a support contract.
If you comes to low level network protocol (e.g. writing a TCP stack), the "network byte order" is always big-endian.
That's a serialization format.
It goes without saying that all binary network protocols should document their byte order, and that if you're implementing a protocol documented as big endian you should use ntohl and friends to ensure correctness.
However if designing a new network protocol, choosing big endian is insanity. Use little endian, skip the macros, and just add
#ifndef LITTLE_ENDIAN
#error
Or the like to a header somewhere.