CODEWITHSUNDEEP
c++cdll
Sy Yuan Li
Sy Yuan Li

Reputation: 81

Calling a function from a DLL which is developed in C++ from C

The function in dll has the prototype below

void Foo(int arg1, int& arg2);

The question is, how to declare the function prototype in C?

Is the declaration legal?

void Foo(int, int*);

Upvotes: 5

Views: 224

Answers (2)

user2371524
user2371524

Reputation:

You need an adapter, consisting of a C++ translation unit and a header usable from both C and C++, like this (use better names of course):

adapter.h:

#ifndef ADAPTER_H
#define ADAPTER_H
#endif

#ifdef __cplusplus
extern "C" {
#endif

void adapter_Foo(int arg1, int *arg2);
// more wrapped functions

#ifdef __cplusplus
}
#endif

#endif

adapter.cpp:

#include "adapter.h"
// includes for your C++ library here

void adapter_Foo(int arg1, int *arg2)
{
    // call your C++ function, e.g.
    Foo(arg1, *arg2);
}

You can compile this adapter into a separate DLL or you can have it as a part of your main program. In your C code, just #include "adapter.h" and call adapter_Foo() instead of Foo().

Upvotes: 5

StoryTeller - Unslander Monica
StoryTeller - Unslander Monica

Reputation: 170044

Is the declaration legal?

It is, but it doesn't declare the same function. If you need a C API, you cannot use a reference. Stick to a pointer, and make sure the function has C linkage:

extern "C" void Foo(int, int*) {
   // Function body
}

If you cannot modify the DLL code, you need to write a C++ wrapper for it that exposes a proper C API.

Upvotes: 8

Related Questions