Calling D functions from C

[Pontus Pihlgren]

Matthias Walter skrev:
> Pontus Pihlgren Wrote:
> 
>> Hi all.
>>
>> Its a rather hypothetical I guess, but is it possible to call D 
>> functions from C? If so, are there limitations?
>>
>> Kind Regards,
>> Pontus.
> 
> If you want to really call the D function from C code, compiling with a C compiler, this can get tricky, as the C compiler normally does not know the ABI of D. It therefore does not know in which registers / stack slots to put which argument, etc.
> 
> But you can write a Wrapper routine in D which simply calls your D routine but has an extern (C) calling convention:
> 
> # extern (C) int myFunctionWrapper (char a, int b, char* c)
> # {
> #    return myFunction (a,b,c); // myFunction is a normal D function.
> # }
> 
> With this code you can call myFunctionWrapper from your C code like you do normally. Alternatively you can code all your C stuff in a .d file, putting extern (C) around everything. Then you can call it without a wrapper, too.
> 
> best regards
> Matthias Walter

That sound almost to easy, I thought that extern could only refer to, 
you know, external functions and not to declare new functions.

Looking more closely at the documentation at 
http://www.digitalmars.com/d/2.0/interfaceToC.html verifies it :) I 
guess I must have missed it the first time I read it.

Thanks,
Pontus.