How to call a C++ dll function at runtime ?

[Mike Pliam]

Despite an enormous amount of information available on runtime dynamic linking of DLLs, I cannot get things to work using Win 7 / VS 2010. While there are many pitfalls, my current problem is how to find the 'decorated' names. Here is a snippet of a header file for my dll (lap.dll):

#ifdef LAP_EXPORTS
#define LAP_API __declspec(dllexport)
#else
#define LAP_API __declspec(dllimport)
#endif

#include "Parser.h"


// This class is exported from the LAP.dll
class LAP_API Clap {
public:
	Clap(void);
	~Clap(void);

// Attributes
protected:
	char * m_pList;
	double ** m_fMatrix;
	CParser * m_pParser;

// Operations
public:
	void PutMatrix(double ** pMatrix);
	double ** GetMatrix();
	void DumpMatrix(double ** pMatrix);
	double **CreateMatrix(int nRows, int nCols);
	void FreeMatrix(double ** pMatrix);
	double ** Parse(char * expr);
	int GetOpMode();
	int SaveVariableMap(char * sfile);
	int LoadVariableMap(char * sfile);
	char * GetKeyList();
	char * GetVarList();
	char * GetFunList();
	void AddVariable(TNT::Matrix<double> Mc, char * svarnam);
	int EraseAllVariables();
	int RunScript(char * sfile);
	int ProcessScript(char* sscript);
	
};

and here is the lap.def file:

LIBRARY

EXPORT

	PutMatrix
	GetMatrix;
	DumpMatrix
	CreateMatrix
	FreeMatrix
	Parse
	GetOpMode
	SaveVariableMap
	LoadVariableMap
	GetKeyList
	GetVarList
	GetFunList
	AddVariable
	EraseAllVariables
	RunScript
	ProcessScript

Both lap.dll and the test app compile, but I cannot figure out how to define the correct function prototypes in the test file.

Here's a fragment of the test file. The handle comes back as valid, but I cannot get the proc address correctly:

#include "stdafx.h"

#include <windows.h> 
#include <stdio.h> 

typedef double ** PARSEPROC(LPSTR);

int _tmain(int argc, _TCHAR* argv[])
{
	cout << "Normal Beginning" << endl << endl;

    HINSTANCE hinstLib; 
    PARSEPROC ProcAdd; 
    BOOL fFreeResult, fRunTimeLinkSuccess = FALSE; 
 
    // Get a handle to the DLL module.
 
    hinstLib = LoadLibrary(TEXT("lap.dll")); 
 
    if (hinstLib != NULL) 
    { 
		printf("\nHandle is valid\n");

		ProcAdd = (PARSEPROC) GetProcAddress(hinstLib, "Parse"); 
        // If the function address is valid, call the function.
 
        if (NULL != ProcAdd) 
        {
			printf("\nProcAdd is not NULL\n\n");

            fRunTimeLinkSuccess = TRUE;
        }
        // Free the DLL module.
 
        fFreeResult = FreeLibrary(hinstLib); 
    } 

    // If unable to call the DLL function, use an alternative.
    if (! fRunTimeLinkSuccess) 
        //printf("Message printed from executable\n"); 
		printf("Unable to call the DLL function\n");

	printf("\n\nNormal Termination\n\n");


	getchar(); 

	return 0;
}

All my efforts have failed to capture the procedure address. In fact, the way the test app is written here, it will not compile as it will not allow assignment (or casting) of the GetProcAddress, even though GetProcAddress(hinstLib, "Parse"); by itself will compile and run. I am uncertain whether this problem is due to name decoration, test app syntax, def file syntax, or some other problem.

There used to be a way to set the compiler to generate docorated names file when compiling a dll, but I can not find such a tool in VS 2010. The DumpBin.exe tool needed to have the path to mspdb100.dll set. When run against lap.dll, it DumpBin produces the following :

File Type: DLL

  Summary

        2000 .data
        3000 .idata
       18000 .rdata
        7000 .reloc
        1000 .rsrc
       BA000 .text
       59000 .textbss

which I have no clue as to what it means.

Any help greatly appreciated. But I've looked at a number of tutorials and most are either outdated or deal only with C declared function. It is worth noting that lap.dll has performed flawlessly when used as a staically bound dll.