As for your 2nd question : cl /Gz double_test double.lib

Aaah ... I see. Thanks. (You meant "double_test.c", not "double_test".)

As regards http://msdn.microsoft.com/en-us/library/x7kb4e2f.aspx, it says there that __cdecl is decorated with a leading underscore, yet dumpbin /exports reports that there is no leading underscore when I build with __cdecl (/Gd). On the other hand, what is written on that page regarding __fastcall (/Gr) and __stdcall (/Gz), is in complete agreement with what dumpbin /exports reports for dll's built with those calling conventions.

I have just managed to build a dll that Win32::API can access ... but only if the function being accessed takes no arguments.

Cheers,
Rob