MATLAB: Best practice for C files in matlab 64bit

mex dll 64bit ms visual studio

I'm using Microsoft Visual Studio Express 2012 (64 bit) and Matlab 2013b (64bit) on win7. I'm having some problems with importing and writing dll libraries that work in Matlab. I have looked around and found that this is a quite common problem.
Could Matlab pose a best practice solution for this problem?
Right now I use
test.h:
#ifdef __cplusplus
extern "C"
{
#endif
   double return_my_double(double x);
#ifdef __cplusplus
}
#endif
test.cpp:
#include "lhr_test.h"
#ifdef __cplusplus
extern "C" {
#endif
  double return_my_double(double x)
  {
    return x;
  }
#ifdef __cplusplus
}
#endif
I compile this without warnings in ms visual studio. In matlab I type
>> unloadlibrary('Project1');
>> loadlibrary('Project1', 'test.h');
Warning: The function 'return_my_double' was not found in the library 
> In loadlibrary at 403 
>> libisloaded('Project1')
ans =
       1
>> m = libfunctions('Project1')
m =
       []
>>
So clearly, matlab loads the library but fails to find the function…
Lars

Best Answer

Clearly the DLL does not export the "return_my_double" function. Recompile your code correctly and make sure the function is really exported. You can double check which functions are exported with tools like dependecy walker.
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