Detection of endian memory ordering. There are four defined macros in this header that define the various generally possible endian memory orderings:
The detection is conservative in that it only identifies endianness that it knows for certain. In particular bi-endianness is not indicated as is it not practically possible to determine the endianness from anything but an operating system provided header. And the currently known headers do not define that programatic bi-endianness is available.
This implementation is a compilation of various publicly available information and acquired knowledge: