I have a two questions about calling C functions from D.

(1) When passing a D callback to a C function, is there a way to write the code without having to prefix the callback declaration with "extern(C)"?

It's not a big deal adding the prefix to the D function declaration. It just seems odd to me to prefix D code with "extern(C)". For example, the following code works:

  extern(C) void cfunc(void function(int));
  extern(C) void dcallback(int x) {...}         <-- Why extern(C)?

Can this be rewritten, dropping the prefix from the second line? If not, it would be helpful to know why "extern(C)" is needed here too.

(2) Is there a way to restrict the invocation of a linked C function to one specific D function?

If the C header is defined in one of the core.stdc libraries, the import statement can either be global or inside a specific D function -- both work. In contrast, when the C function prototype is written directly into the D program (as above), the linker complains unless this declaration is made global. If it's possible to restrict the scope of the C function to just one D function, I'll take advantage.

(I'm using dmd, if that makes a difference.)


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