[Qt-interest] Loading DLL Functions with QLibary fails with "Run-Time Check Failure"

[Matthias Pospiech]

I have a libary which I only want to load if selected.

The vendor header file looks like this:

#ifdef USMCDLL_EXPORTS
#define USMCDLL_API __declspec(dllexport)
#else
#define USMCDLL_API __declspec(dllimport)
#endif

#ifdef __cplusplus    // C++
extern "C" {
//
//     The USMC_Init function initializes driver and returns devices 
information
//
USMCDLL_API DWORD USMC_Init( USMC_Devices &Str);        // OUT - Array 
of structures describing all divices (may be NULL) MUST NOT be deleted

-------------------------------
I changed it to:

typedef DWORD (__stdcall *fn_USMC_Init)( USMC_Devices &Str);

class USMCDLL
{
public:
    USMCDLL(void){}
    ~USMCDLL(void)     {         m_Dll.unload();     }

public:
    bool DllLoaded()     {         return m_Dll.isLoaded();     }
    void unloadDLL()     {          m_Dll.unload();    }
    bool LoadDLL()     { 

        m_Dll.setFileName(QString("USMCDLL.dll"));
        m_Dll.load();
        if (!m_Dll.isLoaded())
            return false;
       
        USMC_Init                    = 
(fn_USMC_Init)(m_Dll.resolve("USMC_Init"));

protected:
    QLibrary m_Dll;

public:
    fn_USMC_Init                    USMC_Init;
};

this however does not work (it compiles). At runtime I get the error:

Run-Time Check Failure #0 - The value of ESP was not properly saved 
across a function call.  This is usually a result of calling a function 
declared with one calling convention with a function pointer declared 
with a different calling convention.

How can I get around this problem?

Matthias