Using a C++-function that is exported

Question

I have been googling for days now, and I cant seem to wrap my head around this problem.

I have a header, which exports some functions to a library. This file is called test_extern.h, and the function looks like this:

__declspec(dllexport) int aFunction(int a, int b);

I have two other files, one .h and .cpp which calculates some things with the help of the exported file. I have stripped down the versions to show what I want to do.

A.h file:

// Include CBaseDILI_J1939 header file.
class A : public CBaseDILI_J1939
{
public:
  int bFunction(int a, int b);
}

A.cpp file:

#include "test_extern.h"
#include "A.h"

int A::bFunction(int a, int b) {
  return aFunction(a, b);  // REturn the value of the exported function!
}

Now when I run this, I get "error LNK2019: unresolved external symbol _imp_aFunction".

I have read and read all there is about exporting dll's, is there anyone who knows what I might be doing wrong?

What library file(s) are you specifying when you run the linker? — Jerry Coffin, Aug 07 '13 at 14:31
I dont add anything extra to the linker. Do I have to do that? I just supposed that the linker would find it — Pphoenix, Aug 07 '13 at 14:39
So, is A in a different project to aFunction? In that case the declaration from the header isn't enough. Do you have a lib from the dll or not? — doctorlove, Aug 07 '13 at 14:46
@Karadur solved it! I had forgotten to import the functions before I used them. Easy fix, but oh so hard to find when you've been staring at the code for hours ;) — Pphoenix, Aug 07 '13 at 14:51
@JerryCoffin You were right. I had too specify the .lib file when I rebuilded the solution, or the linker wouldn't find my functions. — Pphoenix, Aug 08 '13 at 07:56

score 2 · Accepted Answer · answered Aug 07 '13 at 14:33

2

You have to declare the dll function in the calling module as dllspec(dllimport).

answered Aug 07 '13 at 14:33

Karadur

1,226
9
16

Thank you so much! Haha, so simple, but yet so hard to find! – Pphoenix Aug 07 '13 at 14:47

score 2 · Answer 2 · answered Aug 07 '13 at 14:37

2

@Karadur is right.

Check the example on this link: http://msdn.microsoft.com/en-us/library/799kze2z.aspx. The answer is on the bottom of this page.

In A.cpp add this on top.

__declspec(dllimport) int aFunction(int a, int b);

answered Aug 07 '13 at 14:37

ipinak

5,739
3
23
41

Do not forget to check msdn, you will find a lot of helpful posts for windows development. Despite the fact I don't like MS and that I don't develop a lot on their platforms. Their support is by far one of the best... – ipinak Aug 07 '13 at 14:51

Using a C++-function that is exported

2 Answers2