error in using calllib

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Bency Baby
Bency Baby on 14 Dec 2012
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
  1 Comment
Philip Borghesani
Philip Borghesani on 17 Dec 2012
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?

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Answers (2)

Walter Roberson
Walter Roberson on 14 Dec 2012
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.)
  3 Comments
Walter Roberson
Walter Roberson on 17 Dec 2012
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
Philip Borghesani on 17 Dec 2012
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.

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Philip Borghesani
Philip Borghesani on 17 Dec 2012
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.

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