connecting matlab to c++ language dll

hello

i'm trying to use clllib function in matlab i put .dll file and .h file in the same directory as the .m MATLAB file being developed and after that i try to use loadlibrary function bui it have two warnings:

l oadlibrary('t1.dll','T1Header.h') Warning: Message from C preprocessor: lcc preprocessor error: C:\Users\MAHNAZ\Documents\MATLAB\T1Header.h:1 Could not find include file iostream lcc preprocessor warning: C:\Users\MAHNAZ\Documents\MATLAB\T1Header.h:18 No newline at end of file

when i want to use calllib function like this:

calllib('t1', 'Add', 2,3)

matlab give me an error:

??? Error using ==> calllib
Method was not found.

my header file is:

#include <iostream>
#ifndef _T1_HEADER_H_
#define _T1_HEADER_H_

#if defined DLL_EXPORT

#define DECLDIR __declspec(dllexport)

#else

#define DECLDIR __declspec(dllimport)

#endif

extern "C"
{

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

     __declspec(dllexport)  void Function( void );
  }

#endif

i use visual c++ 2010

Any suggestions on what is wrong, what I could do to fix this error, or what else I could try to call this .dll from within MATLAB?

thanks!

Answer 1

[Titus Edelhofer]

Hi,

did you tell MATLAB to use visual studio as well? Looks as if it uses LCC, the C compiler that comes bundled with MATLAB. Do a

mex -setup

and choose your visual studio, that should help.

Titus

[Mahnaz]

thanks

i use Matlab 7.6.0(R2008a) and i have Visual Studio 2010 installed. However, MATLAB doesn't find the compiler. when i want to do this:

>> mex -setup Please choose your compiler for building external interface (MEX) files:

Would you like mex to locate installed compilers [y]/n? n

Select a compiler:

[1] Intel C++ 9.1 (with Microsoft Visual C++ 2005 linker)

[2] Intel Visual Fortran 10.1 (with Microsoft Visual C++ 2005 linker)

[3] Intel Visual Fortran 9.1 (with Microsoft Visual C++ 2005 linker)

[4] Lcc-win32 C 2.4.1

[5] Microsoft Visual C++ 6.0

[6] Microsoft Visual C++ .NET 2003

[7] Microsoft Visual C++ 2005

[8] Microsoft Visual C++ 2005 Express Edition

[9] Microsoft Visual C++ 2008

[10] Open WATCOM C++

[11] Open WATCOM C++ 1.3

[0] None

Compiler: 9

The default location for Microsoft Visual C++ 2008 compilers is C:\Program Files\Microsoft Visual Studio 9.0, but that directory does not exist on this machine.

Use C:\Program Files\Microsoft Visual Studio 9.0 anyway [y]/n? y

Please verify your choices:

Compiler: Microsoft Visual C++ 2008 Location: C:\Program Files\Microsoft Visual Studio 9.0

what should i do? install visual C++ 2008?

[Kaustubha Govind]

This is the list of supported compilers for R2008a - Visual Studio 2010 is not on the list, which is why "mex -setup" doesn't find it. I would recommend installing one of the supported compilers and answer "y" to "Would you like mex to locate installed compilers [y]/n?" - because if MATLAB is unable to find your compiler automatically, there is usually something wrong with your compiler setup.

(Note: You cannot use the LCC compiler to preprocess a C++ header, because it is a C-only compiler, so Titus' solution of converting your header to C-style should work with LCC)

Answer 2

[Titus Edelhofer]

Hmm, I just took another look on your question: probably the easiest thing to do is to write a second header file just containing the declarations:

extern int Add( int a, int b );   
extern void Function( void );

and use this file to call loadlibrary.

Titus

[Mahnaz]

i changed my header file:

#ifndef _T1_HEADER_H_

#define _T1_HEADER_H_

extern int Add( int a, int b );  

extern void Function( void );

#endif

my source file is:

#include <iostream>

#include "T1Header.h"

     extern int Add( int a, int b )
     {
        return( a + b );
     }

     extern void Function( void )

     {

        std::cout << "DLL Called!" << std::endl;
     }

i built the project

when i want to use loadlibrary function:

>> loadlibrary('t1.dll', 'T1Header.h')

Warning: Message from C preprocessor:

lcc preprocessor error: C:\Users\MAHNAZ\Documents\MATLAB\T1Header.h:1 Could not find include file
<iostream>

lcc preprocessor warning: C:\Users\MAHNAZ\Documents\MATLAB\T1Header.h:21 EOF inside comment

> In loadlibrary at 351

Warning: The function 'Add' was not found in the library

> In loadlibrary at 435

Warning: The function 'Function' was not found in the library

> In loadlibrary at 435

and for calllib function:

>> calllib('t1', 'Add', 2,3)

??? Error using ==> calllib

Method was not found.

i think i should insall visual C++ 2008

[Titus Edelhofer]

iostream is C++, lcc is C, so you need to

- remove the "include iostream" line

- add #include <stdio.h>

- replace the cout line by

printf("DLL Called.\n");

Titus

[Guilherme]

I have the exactly same error with Visual Studio 2008