Compiler Error C3368

'function declaration' : invalid calling convention for IDL

You can only use the __stdcall or __cdecl calling conventions in an .idl file.

The following sample generates C3368:

// C3368.cpp
// processor: x86
[idl_module(name="Name", dllname="Some.dll")];

[idl_module(name="Name")]
int __fastcall f1();   // C3368