Example Attached

Frits van Bommel fvbommel at REMwOVExCAPSs.nl
Fri Feb 13 07:01:55 PST 2009

Mike Parker wrote:
> Heinz wrote:
>> torhu Wrote:
>>> On 10.02.2009 19:51, Heinz wrote:
>>>> Heinz Wrote:
>>>> I attached a rar file with the sources just to see what i'm talking 
>>>> about. The example is from the DMD site. Included is the extern D 
>>>> (ok) and the extern C (fails). To compile open "compile.bat" and to 
>>>> run the programs use "run.bat".
>>> Try this:
>>> alias extern (C) void function(void*) MyDLL_Initialize_fp;
>>> alias extern (C) void function() MyDLL_Terminate_fp;
>>> alias extern (C) MyClass function() getMyClass_fp;
>> Haha! cool man, thanx, it works.
>> I never though it could be the type but adding extern(C), the program 
>> treats variables as C function pointers. I had no idea at all that i 
>> can create extern(C) variables to be trated as C type. I learned 
>> something new today!
>> Thanks again.
> It doesn't affect normal variables. Calling a function through a 
> function pointer, the calling convention still must be known in order 
> for parameters to be properly passed. So any time you define a function 
> pointer to point to a C function or to pass to a C API as a callback, it 
> must have the proper extern linkage.

Actually, extern(C) does affect normal variables. In particular, it 
affects their name mangling. (And if the type of the variable includes a 
'raw' function pointer type (not an alias/typedef to one), I'm pretty 
sure it also modifies that type to use a C calling convention function 
pointer type)

The example above, though, does not directly affect any variables 
because they're only alias declarations.

More information about the Digitalmars-d-learn mailing list