Problem with basics of including C++ code with coder (coder.ceval)

Hi,

I'm trying to incorporate existing c++ functions into Matlab coder using coder.ceval, but am struggling to even get a basc example working. I've seen the C example here, but am struggling to get even a simple 'hello world working with c++.

I've written a functin 'helloWorld.cpp' as follows:

#include <iostream>
#include "helloWorld.h"

using namespace std;

double helloWorld(double inpt) {
    cout << "Hello World!!!" << endl;
    cout << "Input is " << inpt << endl;
    return inpt;
}

And then made 'helloWorld.h' as follows:

#if defined __cplusplus
extern "C" {
#endif

#ifndef HELLOWORLD_H_
#define HELLOWORLD_H_

double helloWorld(double inpt);

#endif /* HELLOWORLD_H_ */

#if defined __cplusplus
}
#endif

My matlab function is then:

function out = helloWorld(inpt)

%#codegen
if coder.target('MATLAB')
    fprintf('Hello World! \n');
    fprintf('Input number is %d \n', inpt);
    out = inpt;
else
    out = 0;
    source1 = 'helloWorld.cpp';
    coder.updateBuildInfo('addSourceFiles',source1);
    out = coder.ceval('helloWorld',inpt);
end

end

I tried to compile this using the coder app, calling it as:

inpt = 2.0; out = helloWorld(inpt);

But it fails, with the Target Build Log telling me:

helloWorld1.c: In function ‘helloWorld’:
helloWorld1.c:24:3: error: incompatible type for argument 1 of ‘helloWorld’
   return helloWorld(inpt);
   ^
helloWorld1.c:18:8: note: expected ‘const struct emlrtStack *’ but argument is of type ‘real_T’
 real_T helloWorld(const emlrtStack *sp, real_T inpt)
        ^
helloWorld1.c:24:3: error: too few arguments to function ‘helloWorld’
   return helloWorld(inpt);
   ^
helloWorld1.c:18:8: note: declared here
 real_T helloWorld(const emlrtStack *sp, real_T inpt)

What am I doing wrong here?

Cheers,

Arwel

[Walter Roberson]

coder.cinclude() might be needed?

https://www.mathworks.com/help/coder/ug/call-cc-code-from-matlab-code.html

Answer 1

[Darshan Ramakant Bhat]

I changed the MATLAB file name to avoid the clash. Also added coder.cinclude as suggested by Walter.

function out = helloWorldWrapper(inpt)
%#codegen
if coder.target('MATLAB')
    fprintf('Hello World! \n');
    fprintf('Input number is %d \n', inpt);
    out = inpt;
else
    out = 0;
    source1 = 'helloWorld.cpp';
    coder.cinclude('helloWorld.h');
    coder.updateBuildInfo('addSourceFiles',source1);
    out = coder.ceval('helloWorld',inpt);
end
end

I was able create mex using the below command

>> codegen helloWorldWrapper -args {0} -report
Code generation successful: View report

>> helloWorldWrapper_mex(5)
Hello World!!!
Input is 5

ans =

     5

[Arwel]

That's awesome Darshan - thanks very much!