Interfacing C++ to D --> or better: C++ --> C ---> D (DLL)

[evilrat]

On Saturday, 29 March 2014 at 15:03:18 UTC, BeschBesch wrote:
> I want to use a set of functions that rely on a library which 
> is not available for D (Harfbuzz). So I just wrote myself a set 
> a functions that will do anything I need (Init, Free, Fonts, 
> Text, etc).
>
> The DLL is working fine and dynamically linking should work (it 
> does in C++ --> LoadLibrary). Unfortunately, i get Error 42 
> evertime i try to call a function.
>
> As i suspected that some things written by me could be 
> responsible for this, I build a test application with three 
> functions (Test, Test2,Test3), got myself the D-.lib for 
> statical-linking (implib-Dmd) and tried that one out. The 
> result: Error 42.
>
> What did I miss that can still cause linker errors? So far I 
> did:
>
> DLL is written in C (C89 --> VC++ only can afford that one it 
> seems). And yes I changed it to C from C++ in the compiler 
> settings.
>
> DLL has an entry function AND a module-definition file (.def). 
> A .lib-file is created alongside with the DLL (.def specified 
> in porject settings). OF COURSE, I built a D-conform .lib by 
> using implib with /s option (and without) /s option.
>
> Thank you, if you are still reading.
>
> CODE:
> ////// declared in Test.h
> void Test1(void);
> int Test2(int i);
> long Test3(int* ptr);
> ////// Example implementation in Test.c (include "test.h"
> void Test1(void)
> {
> 	printf("FUNCTION WAS CALLED\n");
> }
> ///// .def-File
> LIBRARY "CtoDtestDll"
> EXPORTS
> Test1 @1
> Test2 @2
> Test3 @3
> /// SETTINGS (C++)
> Calling-convention: __cdecl (= std. ??)
> Compiling for:   C (/TC)
> /// SETTINGS (LINKER)
> Modul-definition-file: CTestDll.def....
>
> ////// D-Module for usage with .lib from .dll (implib! from bup)
> module CoreFuncs; // just a name
>
> pragma (lib,"CtoDtestDll.lib"); // statically linking (could 
> user settings too)
>
> extern (C)   /// needed so the compiler can link the functions
> {
>
> void Test();
>
> }

have you looked at exported symbols in dll? it may be C++ from 
what you said(lib not designed for C++?), so you can try 
extern(C++) on D side instead extern(C). or add manually #ifdef 
__cplusplus and extern "C" on lib side(if its not that big of 
course).