I have written some code in C++ using Octave API and this C++ function basically calls an Octave script, but it is giving segmentation fault

Question

I want to write C++ code using Octave API for C++ which will use an Octave function. I am attaching my code.

#include <iostream>
#include <unistd.h>
#include <octave/oct.h>
#include <octave/octave.h>
#include <octave/parse.h>
#include <octave/toplev.h>
#include <interpreter.h>

int main()
{
        // arguments for octave
        string_vector argv (2);
        argv(0) = "embedded";
        argv(1) = "-q"; // quiet

        // start octave, run embedded (third parameter == true)
        octave_main (2, argv.c_str_vec (), true);

        // read the script file
        source_file("calc_and_plot.m");

        // call the function with an argument
        octave_value_list in;
        in(0) = "Hello, world.";
        feval("calc_and_plot", in);

        std::cout << "octave (child process) done\n";
        clean_up_and_exit(0); // quit octave. This also quits the program,
                              // so use this together with atexit, if you 
                              // need to do something else after octave exits
    
    return 0;
}

My Octave script file is:

function calc_and_plot(str)
    printf('%s\n', str);
    x = linspace(0, 2*pi, 100);
    y = sin(x);
    it = plot(y);
    waitfor(it);
end

I am getting Segmentation fault (core dumped) .
I execute the code using the terminal by running " mkoctfile --link-stand-alone file_name.cpp -L/usr/lib/octave-4.2.2 -I/usr/include/octave-4.0.2 -loctave -loctinterp -o file_name &&./file_name ". I am using Octave 4.2.2 and it is installed in Ubuntu 18.04. Please help me this this matter.

Answer 1

I don't know exactly what's wrong with your code, but you seem to be mixing styles and libraries from different versions of octave.

Eg toplev.h is deprecated in newer versions of octave, and has been replaced by interpreter.h. Yet you seem to be trying to include both headers...

Equally, I think octave_main is no longer used (but maybe it was back in 4.2.2?)

Also from -L/usr/lib/octave-4.2.2 -I/usr/include/octave-4.0.2 I can see you're trying mix octave v4.2.2 libraries with v4.0.2 headers, etc... no wonder it's segfaulting!

---

Why are you even using such an old version of octave? The latest is 6.2.0. Do you have a particular reason for needing to use an older version?

If not, my advice would be to download and install the latest octave from source, and follow the instructions on how to create a standalone program from the manual here: https://octave.org/doc/v6.2.0/Standalone-Programs.html

If you require v4.2.2 specifically, then download and install that from source, and try to follow the instructions from the manual for that version specifically, eg: https://octave.org/doc/v4.2.2/Standalone-Programs.html

PS: note the changes in the manual between versions 4.02, 4.22, and 6.20... eg 4.02 uses toplev, but 4.22 does not. 4,22 uses octave_main. but 6.20 does not...