error in using calllib

I am using Microsoft visual studio 2008 and MATLAB 7.11.0(R2010b) i want to use callib function but it shows me an error?

>> loadlibrary('t1.dll', 't1header.h')

>> calllib('t1','Add',2,3) ??? Error using ==> calllib Method was not found.

please help me

[Philip Borghesani]

Do you recive any warnings when you load the library? What is the output of libfunctions t1? If you issue the command:

NotFound=loadlibrary('t1.dll', 't1header.h');

What is the content of NotFound?

Answer 1

[Walter Roberson]

That could mean that Add was not found in the library.

In the code that defines Add, is that code C or C++ ? If it is C++, is it in a

extern "C"

section? If it is C++ and is not in an extern C section, then internally it would not be known by the name Add . (This is a deliberate design feature of C++ in order to prevent accidental calling of a C++ routine without a proper "this" object in place.)

[Bency Baby]

T1Header.h ----------

#ifndef _T1_HEADER_H_

#define _T1_HEADER_H_

/*check if the compiler is of C++*/
#ifdef __cplusplus 
extern "C" {
  int Add( int a, int b );
  
}
#endif
#endif

T1Header.cpp

------------

#include "stdafx.h"

#include <stdio.h>
#include "T1Header.h"
     extern "C" int Add( int a, int b )
     {
        return( a + b );
     }

These are the files.

still this error is coming

calllib('T1Header','Add',2,3) 
??? Error using ==> calllib Method was not found.

[Walter Roberson]

I'm sure I answered this...

You are attempting to call upon a function named Add, passing to it two double numbers. Your routine defines a function named Add that accepts int numbers. You must match the type of parameter you are passing with the type of parameter the routine accepts.

Reminder, in MATLAB,

A = 2

defines A to be double, not integer. It is exactly the same as if you had used

A = 2.0000000;

or

A = 0.02E+2

Whereas

A = uint8(2)

would assign an 8 bit unsigned integer to A.

The number of bits in an "int" depends upon your C++ compiler.

[Philip Borghesani]

Calllib will automatically convert all simple data types for you. The types are not the problem. Matlab matrices are also automatically converted to native pointer types to a vector/matrix.

Answer 2

[Philip Borghesani]

Given the header and code you posted it looks like you are not exporting your function from the library. Read up on building a DLL with exported functions and the declspec compiler extension. Dependency walker can be used to verify that the function was correctly exported without name mangling.