Using a class inside a dll

Question

I have a class inside a dll which I want to use in another project. I read this tutorial about how to do this and my pseudo code looks like this

interface.h

#ifdef  EXPORT
#define SOMEAPI __declspec(dllexport)
#else
#define SOMEAPI __declspec(dllimport)
#endif

struct ISomeInterface
{
  virtual void SomeMethod()=0;
};

typedef ISomeInterface* SOMEHANDLE;

#define EXTERN_C     extern "C"

EXTERN_C SOMEAPI SOMEHANDLE WINAPI CreateSomething(VOID);

And then I have SomeDLL.dll which implements ISomeInterface and CreateSomething.
When I try to use this in my client I get linker error. The client looks like this:
Client.cpp

#include "interface.h"
SOMEHANDLE h = ::CreateSomething();  // Linker error here: Unresolved external

I can solve this by adding the dll project as a dependency of Client project in VC++. Then everything is good.
The problem is what if I want to use this a standalong dll(which is the case right now)? How do I get rid of the linker error then?

You may need to provide a static lib, that allows loading the dll at runtime and wraps the interface for your client. Have a look [here](http://stackoverflow.com/questions/3360828/plugin-pattern-with-dll-how-can-i-extract-plugin-interface-from-dll) — πάντα ῥεῖ, Nov 10 '12 at 12:34

score 0 · Accepted Answer · answered Nov 10 '12 at 16:06

0

I can solve this by adding the dll project as a dependency of Client project

Yes, that automatically does the one thing you have to do in a stand-alone project by hand. Project + Properties, Linker, Input, Additional Dependencies setting. Add the .lib file that was generated by the DLL project. The import library, it tells the linker about the functions exported by the DLL.

answered Nov 10 '12 at 16:06

Hans Passant

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Thank you. I managed to solve this problem by adding `#pragma comment(lib, "FormatDriveDLL.lib")`. But you're doing this automatically. – atoMerz Nov 12 '12 at 09:19

Using a class inside a dll

1 Answers1