Please Help With C DLL

[Matthew Hanna]

I am writing a short OpenGL application in Visual Basic. I need an
extension that I can't get from the VB side. I create a dll named
glFogCoordf_Vb. dll to do the work for me. The dll fails to see the OpenGL
commands. I am at a loss as to how this can be fixed. Any ideas on how to
fix the problem? The dll is being created in MS Visual C/C++ 6.0 using the
Win32 Dynamic-Link Library Wizard. My code is as follows...

-- glFogCoordf_vb. def --
LIBRARY glFogCoordf_vb

DESCRIPTION 'Volume Fog OpenGL Extension'

EXPORTS
glFogCoordfEXT

-- glFogCoordf_vb. h --
#ifdef GLFOGCOORDF_VB_ EXPORTS
#define GLFOGCOORDF_VB_ API __declspec(dlle xport)
#else
#define GLFOGCOORDF_VB_ API __declspec(dlli mport)
#endif

GLFOGCOORDF_VB_ API void APIENTRY glFogCoordfEXT( const float fCoord);

-- glFogCoordf_vb. cpp --
#define WIN32_LEAN_AND_ MEAN // Exclude rarely-used stuff from Windows
headers

#include <windows.h>
#include <olectl.h>
#include <gl\gl.h>
#include "glFogCoordf_vb .h"

#pragma comment( lib, "opengl32.l ib" )

typedef void (APIENTRY * PFNGLFOGCOORDFE XTPROC) (GLfloat coord); // Declare
Function Prototype
PFNGLFOGCOORDFE XTPROC glFogCoordfEXT_ func = NULL; // Our glFogCoordfEXT
Function

int Extension_Init( )
{
char Extension_Name[] = "EXT_fog_coord" ;

MessageBox(NULL , "Checkpoint 1", "Message", MB_OK);

// Allocate Memory For Our Extension String
char* glextstring=(ch ar *)malloc(strlen ((char
*)glGetString(G L_EXTENSIONS))+ 1);

MessageBox(NULL , "Checkpoint 2", "Message", MB_OK);
strcpy (glextstring,(c har *)glGetString(G L_EXTENSIONS)); // Grab The
Extension List, Store In glextstring

MessageBox(NULL , glextstring, "Extensions ", MB_OK);
if (!strstr(glexts tring,Extension _Name)) // Check To See If The
Extension Is Supported
return FALSE; // If Not, Return FALSE

free(glextstrin g); // Free Allocated Memory

// Setup And Enable glFogCoordEXT
glFogCoordfEXT_ func = (PFNGLFOGCOORDF EXTPROC)
wglGetProcAddre ss("glFogCoordf EXT");

return TRUE;
}


BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_c all,
LPVOID lpReserved
)
{
switch (ul_reason_for_ call)
{
case DLL_PROCESS_ATT ACH:
/* if (!Extension_Ini t()) {
return FALSE;
}
*/
case DLL_PROCESS_DET ACH:
glFogCoordfEXT_ func = NULL;
break;
}
return TRUE;
}

GLFOGCOORDF_VB_ API void APIENTRY glFogCoordfEXT( const float fCoord)
{
if (glFogCoordfEXT _func == NULL) {
Extension_Init( );
}

if (glFogCoordfEXT _func != NULL) {
glFogCoordfEXT_ func((GLfloat)f Coord);
}
}



I get past Checkpoint 1 but the dll bombs on glGetString which I assume
means that the function isn't there. I have tried stepping through the code
during debug and it goes straight to strlen and complains about an invalid
memory address. This code was taken from a C application I wrote and it
works fine there. The OpenGL in the VB application works fine as well; as
long as I don't let it execute the call to the dll. Any help would be
greatly appreciated.

Thanks!
Matthew Hanna

[Thomas Matthews]

Re: Please Help With C DLL

Matthew Hanna wrote:[color=blue]
> I am writing a short OpenGL application in Visual Basic. I need an
> extension that I can't get from the VB side. I create a dll named
> glFogCoordf_Vb. dll to do the work for me. The dll fails to see the OpenGL
> commands. I am at a loss as to how this can be fixed. Any ideas on how to
> fix the problem? The dll is being created in MS Visual C/C++ 6.0 using the
> Win32 Dynamic-Link Library Wizard. My code is as follows...[/color]
[snip]
[color=blue]
> Thanks!
> Matthew Hanna
>[/color]

You need help from the experts in a Microsoft newsgroup.
This newsgroup, news:comp.lang. c++, only discusses the _standard_
C++ language which has no facilities for DLLs or OpenGL.

See the FAQ and welcome.txt links below.

--
Thomas Matthews

C++ newsgroup welcome message:

http://www.slack.net/~shiva/welcome.txt

C++ Faq: http://www.parashift.com/c++-faq-lite
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alt.comp.lang.l earn.c-c++ faq:

http://www.raos.demon.uk/acllc-c++/faq.html

Other sites:
http://www.josuttis.com -- C++ STL Library book