Making an executable with input arguments using codegen

I'm trying to compile a Matlab code using codegen and making an executable. The thing is that after compilation, I can't seem to successfully call the app from matlab along with the relevant input. I'll explain:

To make things simple, let's assume that the purpose of my program is to create a '.txt' file named 'my_text.txt' and print an input string inside, like so:

function PrintMyString(input_str) %#codegen

      fid = fopen('my_text.txt','w');
      fprintf(fid,'My input string is: %s',input_str);
      fclose(fid);

end

Now, I tried to compile the code above using the following script:

str = 'pre_defining_the_input_variable_by_example';
codegen -config config_obj PrintMyString -args {str}

when config_obj is the code generation configuration defined somewhere earlier.

The compilation was successful, but as I mentioned before, when I tried to activate the program it didn't go as planned. I tried various options for calling, such as:

system(['PrintMyString.exe ',str]);

The text file was created, but no input string was printed (all that appeared was the line "My input string is: ").

I also tried adding a main function that calls the original PrintMyString function, like so:

function main() %#codegen

      str = 'some_string';
      PrintMyString(str);

end

I compiled it like that:

str = 'pre_defining_the_input_variable_by_example';
codegen -config config_obj main PrintMyString -args {str}

And that worked, but obviously it doesn't help because the input string has to be sent to the program from outside.

Any ideas? What am I doing wrong?

Answer 1

[Titus Edelhofer]

Hi,

it's probably not a question of the code generation but your main file: you compile to an executable, so probably your config_obj carries the information about the main file that you have to have. This main file should be able to take string input and pass it to the generated C code.

Maybe you can share your main file and we can take a look.

Titus

[Yuval Geyari]

Hi Titus, thanks for your answer.

The main file is as I presented:

function main() %#codegen

        str = 'some_string';
        PrintMyString(str);

end

I wish for something like this (it didn't work):

function main(str) %#codegen

        PrintMyString(str);

end

This or any other way which will allow me to pass an input argument into my executable using the system function, or the dos function, or the bang operator (!).

As for config_obj, the only thing I did with it before using codegen was this:

config_obj = coder.config('exe','ecoder',false);

I don't actually know what this line is for, but I understand that it has something to do with choosing the Matlab Coder. Just to be clear, this is the main compiling script:

config_obj = coder.config('exe','ecoder',false);
str = 'pre_defining_the_input_variable_by_example';
codegen -config config_obj main PrintMyString -args {str}

The main compiled function "main" is in a different '.m' file:

function main() %#codegen

        str = 'some_string';
        PrintMyString(str);

end

And last, the printing function which is also in a different '.m' file:

function PrintMyString(input_str) %#codegen

        fid = fopen('my_text.txt','w');
        fprintf(fid,'My input string is: %s',input_str);
        fclose(fid);

end

I'm sorry if it's too obscure, if there's anything else you'd like me to add just let me know!

[Titus Edelhofer]

Hi,

there is a misunderstanding: the main function needs to be a pure C function. Take a look here where the work flow is described. Basically, in the codegen/PrintMyString/example/main.c an example main file is generated. Take this, adapt to your need and add while compiling your code with -a myadaptedmain.c

Titus

[Yuval Geyari]

Hi Titus, you really helped me! But still something doesn't work.

I am now trying to compile the code using the Coder App, which seems to be more convenient than using codegen.

The new main.c file is pretty simple:

#include "PrintMyString.h"
#include "PrintMyString_initialize.h"
#include "PrintMyString_terminate.h"

int main( int argc , char* argv[] ) {

PrintMyString_initialize();

PrintMyString( argv[1] );

PrintMyString_terminate();

return 0;

}

After creating the main.c file, I've attempted to compile the code, unsuccessfully. In the Error Report I've noticed the following line:

gmake: *** No rule to make target 'D:/Programs/ProjectFolder.lib', needed by 'D:/Programs/ProjectFolder/PrintMyString.exe'. Stop.

When 'D:/Programs/ProjectFolder' is the path to the directory ProjectFolder in which the original PrintMyString.m file is located, along with the new main.c file.

What is this '.lib' file mentioned in the error line? I cannot seem to figure it out. Any ideas?

[Titus Edelhofer]

Hi,

this is what I did: I used the coder app as well and

• specified myself the input to be char of size 1x:Inf(to have strings of undefined length as input).
• Selected executable
• Generated code
• Copied the generated example\main.c, main.h to mymain.c, mymain.h
• Made some changes (here the changed lines):

#include "mymain.h" // instead of #include "main.h"
static void main_PrintMyString(const char* str)  // add str as input
input_str = emxCreateWrapper_char_T(str, 1, strlen(str)); // rows=1, cols = length of the input string
main_PrintMyString(argv[1]); // second input is the input parameter (first is the name of the executable)

• and added mymain.c on the "More Settings"->Custom Code->Additional Source files
• and generated code again
• and if everything works fine, call the executable :)

Titus

[Yuval Geyari]

It works great, thank you! Althougth I used a different input argument in the last line you mentioned:

main_PrintMyString(input_str);

And also, how exactly did you know to use the emxCreateWrapper_char_T function? It wasn't in the original example main.c file.