QuentinC wrote: > AS I guessed, the compiler exported round2 as round2@8. The FFI looks for _round2@8 (with a prepended underscore), because that's what the Microsoft docs tell us: http://msdn.microsoft.com/en-us/library/zxk0tw93(v=vs.110).aspx and that's what GCC generates on Windows for a __stdcall function: [...] .globl _round2@8 .def _round2@8; .scl 2; .type 32; .endef _round2@8: [...] --Mike