Matlab function handles and C++ function pointers - c++

Question

Is it possible to make a Matlab function handle compatible with a C++ function pointer? I am trying to call a C++ function from Matlab that takes in a C++ function pointer. For example:
C++:
void Cfunction( C++functionPointer);
Matlab:
function out Mfunction(functionHandle)
out= Cfunction(functionHandle)
Unfortunately I can not post the code because it is confidential. So I want my Matlab program to call a C++ function using calllib(). One of the parameters for the C++ function is a function pointer. In Matlab, I tried using a Matlab function handle as the parameter in callib but this did not work. Therefore, I am having difficulty calling the C++ function from Matlab.
Matlab is saying that the C++ compiler will not accept the Matlab function handle type for its pointer argument.
Thanks

Answer 1

Ok, so, from what I understand, you have a library written in C++ with a function (let me call it functionFromMyCppLibrary) that you nee to run. One of the arguments this function requires is a function pointer.
I'm assuming this function pointer must be a C++ function. If functionFromMyCppLibrary needs to call an arbitrary Matlab function, then my answer does not apply. However there's a Q&A in the Mathworks exchange that you might find helpful: How do I pass function handles to C++ mex function in MATLAB 7.8 (R2009a)?. You will probably need to modify CppFunction below so that it makes Matlab call feval. It gets actually easier if you can hardcode a Matlab function name in CppFunction().
callTheCppThing.cpp:
#include "mex.h"
#include "myCppLibrary.h"
void CppFunction()
{
// The function your C++ library requires as a function pointer
// You could use mexCallMATLAB here to call a Matlab function,
// but it will get trickier if you can't hard-code the name of
// the Matlab function here
}
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, mxArray *prhs[])
{
// Process however you need the arguments
functionFromMyCppLibrary(CppFunction);
// Create the output variables and return whatever Matlab needs
}
You can compile with
mex callTheCppThing.cpp
(Add to this command line anything that is required to link this C++ with your library.)
And you call from Matlab with
callTheCppThing
This removes the need of Matlab passing any kind of handle to your C++ library. (If you have no possibility of writing different wrappers in C++, then check the linked Q&A from Mathworks. It's tricky, but possible.)