Good morning, gcc uses a different convention from the Microsoft environment when it comes to laying out fields in C structs, in particular bit fields. Can I pass the -optc--mms-bitfields to ghc when it compiles via C without negative effect? This flag is not implicit at the moment which I assume means that ghc itself is not compiled with --mms-bitfields on Windows. ghc surely includes struct declarations when it compiles the generated C files, so the question is whether all its structs are laid out the same regardless of which layout option one chooses. Thank, Axel.