Using templates to declare function prototypes

[Daniel Murphy]

Use extern(System)?

"Heinz" <malagana15 at yahoo.com> wrote in message 
news:j12hkk$2mcd$1 at digitalmars.com...
> Hello D community!!!
>
> I'm porting the NVIDIA CUDA headers to D. The CUDA platform runs on 
> multiple
> OS, so functions prototypes (in the D way) are declared as 
> "extern(Windows)
> ..." for MS Windows and "extern(C) ..." for other OS'es.
>
> The thing is that there's no "alias extern(X) myextern;" in D to be used 
> like
> this:
>
> version(Windows)
>    alias extern(Windows) myextern;
> else
>    alias extern(C) myextern;
>
> ...
> myextern void cudaFunct1();
> myextern uint cudaFunct2(byte*);
>
> ...The C way to accomplish this is:
>
> #ifdef _WIN32
> #define CUDAAPI __stdcall
> #else
> #define CUDAAPI
> #endif
> ...
> CUresult CUDAAPI cuInit(unsigned int Flags);
>
> It is a bit redundant and dirty to declare all the functions twice. So i 
> made
> a template to declare functions prototypes with the corresponding naming
> convention, here's what i got:
>
> template CUDAAPI(R, P ...)
> {
> version(Windows)
> alias extern(Windows) R function(P) CUDAAPI;
> else
> alias extern(C) R function(P) CUDAAPI;
> }
> ...
> CUDAAPI!(CUresult, uint) cuInit;
>
> This code actually compiles since its syntax is correct but when linking i
> relize that the linker is still looking for the "extern(D)" symbol and by 
> any
> means, no matter where i place the extern(X), the compiler is generating 
> the D
> mangled symbol (_D5cudad4cuda6cuInitPWkZE5cudad4cuda8CUresult, at least 
> the
> template is inserted in the context).
> I've tried with DMD 1.030 and the latest 1.069, both with the same result.
>
> I also did a mixin flavored template that also compiles but is even worse
> because the linker is still stuck with a templated/D mangled symbol, take 
> a look:
>
> template CUDAAPI(string N, R, P ...)
> {
> version(Windows)
> mixin("extern(Windows) R " ~ N ~ "(P);");
> }
> ...
> mixin CUDAAPI!("cuInit", CUresult, uint);
>
> The generated symbol for this code is:
> __D5cudad4cuda55__T7CUDAAPIVG6aa6_6375496e6974TE5cud
> ad4cuda8CUresultTkZ6cuInitWkZE5cudad4cuda8CUresult at 4. As you can see, the
> symbol is still recognized as a template so i discard this code.
>
> I found templates to be a very interesting case of study, templates give
> languages the fun or the exciting part of programming by presenting 
> challenges
> in code complexity but still i can not get some parts of my code to work.
>
> Any aproach or ideas on how to accomplish this template or multi extern
> declaration?
>
> Thank you so much for reading.