Import C++ DLL

[Don Clugston]

Frits van Bommel wrote:
> CrowBar wrote:
>> Please bear with me, I'm very new to C/C++ & D.
>>
>> I want to Import a function from a DLL made with VC++ express edition 
>> into
>> D.
>>
> [snip]
>>
>> The program compiles but does not execute, it returns "Error Access
>> Violation", (it should display the number 42).
>>
>>
> [snip]
>>     fnMyDLL = cast(fnMyDLL_fp) GetProcAddress(h, "fnMyDLL");
>>
>>     printf("value=%i\n", fnMyDLL());
> [snip]
> 
> GetProcAddress is probably returning null, you forgot to check for that. 
> It seems to think the function doesn't exist. The most likely cause is 
> name mangling.
> 
> Try adding an underscore before the first character in the function 
> name. (IIRC that's the mangling for C functions on Windows)
> 
> If that didn't work, make sure the function is either compiled as C code 
> or marked 'extern "C"' (directly or in an 'extern "C" {}' block) if it's 
> compiled as C++ code.

It's incredibly painful to get VC++ to produce extern(C) DLLs. It 
insists on doing something like:
_fnMyDLL at 0
essentially ignoring the "extern(C)" declaration. All the __declspec 
garbage doesn't do much, either. I keep reverting to .DEF files.

However, it should be quite simple to make a Microsoft name mangler as 
as a compile-time function. Hmmm... would make a nice little project.
--
You can also use the coffimplib tool (from the DM ftp site) to convert 
the MS lib to DMD format, and link it statically. Probably easier.