Hi, I am stuck with an odd problem that I don't know how to begin to resolve. I have developed an FFI wrapper around the PBC library. I have a number of tests thatcheck simple operations and some of the more simple examples from the PBC C examples. On FreeBSD and Linux (Mint) all tests pass successfully but on Windows (mingw64) many fail with what look like data corruption errors. I suspect it is something to do with alignment or size calculations but I have no idea how to proceed. The hsc file is fairly standard: data PBCPairing = PBCPairing data PBCElement = PBCElement data PBCField = PBCField data PBCPreProcElement = PBCPreProcElement instance Storable PBCPairing where sizeOf _ = #{size struct pairing_s} alignment _ = #{alignment struct pairing_s} peek = notImplemented poke = notImplemented instance Storable PBCElement where sizeOf _ = #{size struct element_s} alignment _ = #{alignment struct element_s} peek = notImplemented poke = notImplemented instance Storable PBCPreProcElement where sizeOf _ = #{size struct element_pp_s} alignment _ = #{alignment struct element_pp_s} peek = notImplemented poke = notImplemented instance Storable PBCField where sizeOf _ = #{size struct field_s} alignment _ = #{alignment struct field_s} peek = notImplemented poke = notImplemented Generated sizeOf is the same and alignment is 8 across all OSes. I am using inline-c for the FFI. PBC was built using msys2's version of mingw64. All the C examples work correctly in the msys2 shell. Does any one have any ideas on how best to approach this issue? Thanks Sumit