[polyml] FFI conversions that are portable across Poly/ML versions

I am trying to define LargeInt.int conversions for C integer types in terms of those supplied in Foreign in a way that will work with both Poly/ML 5.6 or 5.7. This requires that e.g. - Foreign.cUint64 is used for Poly/ML = 5.6 but - Foreign.cUint64Large is used for Poly/ML >= 5.7 I am thinking of achieving this by having separate SML files for different Poly/ML versions and using the right one as follows:

let val version = PolyML.rtsVersion () in PolyML.use ( if version >= 570 then "src-5.7.sml" else if version = 560 then "src-5.6.sml" else raise Fail "unsupported Poly/ML version" ) end

Is this a future-proof way to choose based on Poly/ML version?

Another option might be to copy the implementation of these conversions from Foreign.sml but that may not be possible - for example I couldn't see how to get the flag bigEndian in an application.

Is there a better way altogether with some compiler trickery?

Phil