Conditionally-compiling based on endianness

Question

I'm reading Words from byte arrays and need to make parts of my code endian-aware. Does GHC expose anything (like MachDeps.h) which I can use to make code conditional on processor endianness? If not can I deduce endianness reliably from HOST_ARCH (from ghcplatform.h accessible in .cabal file with the arch() conditional)? Or other ideas?

Answer 1

Are you looking for something like this: https://hackage.haskell.org/package/cpu-0.1.0/docs/System-Endian.html

If you don't want/cannot use these packages, looking at the source code for the above, you can see how to check endianness on any platform with (almost) any lower-level programming language like C or similar. Fill a part of your stack (for a machine with 4 bits: e.g. 1000) and then read back the LSB or MSB of said stack. The Endianness will determine how it is stored (you'll read back 1000 or 0001).