Errors trying to compile multiple c++ files with mex for MATLAB

Question

I am using MATLAB under Ubuntu and want to compile a set of 2 c++ files with a header file, using mex. I show a basic example and the errors I am getting.

This code produces the text "hello" from the c++ function that begins from the mexFunction and is compiled in MATLAB using mex, (mex mexTryAlex.cpp):

#include <mex.h>
#include <iostream>
using namespace std;

void newfunc(){
    cout<<"hello\n";   
}
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) 
{ 
    newfunc();
}

and it works normally. Now I try to use multiple files and a header file with mex. I create a header file try.h:

#ifndef try_h
#define try_h
void newfunc();
#endif

and then the new function's file try.cpp:

#include <mex.h>
#include <iostream>
#include <try.h>
using namespace std;

void newfunc(){
    cout<<"hello\n";   
}

These 3 files do not compile with mex:

>> mex  mexTryAlex.cpp try.cpp try.h

Warning: You are using gcc version "4.4.3-4ubuntu5)".  The version
     currently supported with MEX is "4.3.4".
     For a list of currently supported compilers see: 
     http://www.mathworks.com/support/compilers/current_release/

try.cpp:4:17: error: try.h: No such file or directory
mex: compile of ' "try.cpp"' failed.
??? Error using ==> mex at 208
Unable to complete successfully.

Another attempt with using the -I option:

>> mex  -I mexTryAlex.cpp try.cpp try.h
Warning: You are using gcc version "4.4.3-4ubuntu5)".  The version
     currently supported with MEX is "4.3.4".
     For a list of currently supported compilers see: 
     http://www.mathworks.com/support/compilers/current_release/

mexTryAlex.cpp:1:17: error: mex.h: No such file or directory
mexTryAlex.cpp:7: error: ‘mxArray’ has not been declared
mexTryAlex.cpp:7: error: ISO C++ forbids declaration of ‘mxArray’ with no type
mexTryAlex.cpp:7: error: expected ‘,’ or ‘...’ before ‘*’ token
mex: compile of ' "mexTryAlex.cpp"' failed.
??? Error using ==> mex at 208
Unable to complete successfully.

How can I get these files to compile?

Just a general advice: using namespace std; is not the best of ideas. Just use std::cout, or if you use cout a lot and want to abbreviate it, use using std::cout;, but opening up the entire std namespace will give you headaches in the long run :) Just look around here on SO for pros/cons/discussions about this topic. — Rody Oldenhuis

Vass Vass · Accepted Answer · 2013-04-22T14:44:46

The error was fixed by using

#include "try.h"

instead of

 #include <try.h>

in the source files.

Errors trying to compile multiple c++ files with mex for MATLAB

1 Answers