In our project we would like to generate APIs like this:

#ifdef XXX
#define MYDLL declspec(dllimport)
#else

MYDLL int f(int);

The function f comes from Rust, and the definition should be generated automatically. However, we would like to somehow annotate that f receives MYDLL, which should be an arbitrary block that can be user-defined.

Depending on how much cross-compilation is going on, the MYDLL block can get large, so it should probably be definable in a separate file.