Issue c++ code system() to call external compiler to compile other c++ code

system("cd the_files_directory");
system("g++ *.h *.cpp -o execute");

The first line spawns a new process, a shell, which executes the command "cd the_files_directory", and exits. Your processes working directory is unaffected by the child process. So you are still in your original directory when you execute the g++ command.

Also, this command tries to compile header (.h) files, which would might cause g++ to fail, but is probably just redundant.

system("g++ the_files_directory/*.h the_files_directory/*cpp -o execute)

Again, you're trying to compile header (.h) files, which might cause g++ to fail, but even if it works, it is creating execute in your current directory and not in the_files_directory. You probably want

system("g++ the_files_directory/*.cpp -o the_files_directory/execute");

Your last variant

system("g++ -fworking-directory the_files_directory/*.h the_files_directory/*cpp -o execute")

Is the same command with debugging information about directories, so it has the same problems as above.

Given ('tfd' for 'the_files_directory'):

tfd/foo.cpp

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

void foo() {
    std::cout << "foo\n";
}

tfd/foo.h

extern void foo();

tfd/test.cpp

#include "foo.h"

int main() {
    foo();
}

And at the top level, comp.cpp

#include <stdlib.h>

int main() {
    system("g++ tfd/*.cpp -o tfd/execute");
}

I did the following:

osmith@vbx:~/tmp$ g++ -Wall -std=c++14 comp.cpp -o compiler

Execute the compiler:

osmith@vbx:~/tmp$ ls tfd
foo.cpp  foo.h  test.cpp
osmith@vbx:~/tmp$ ./compiler
osmith@vbx:~/tmp$ ls tfd
execute  foo.cpp  foo.h  test.cpp

Now test the resulting executable:

osmith@vbx:~/tmp$ tfd/execute
foo

-Guys! I found my own solution last night! -Here are my steps which will surely work after so much experiment for different ways by myself before you guys posts!

-Step1: -Move my whole project out from Qt project location and remove .pro and other files generated by Qt and just keep my own .cpp files and .h files. I was doubting if Qt is too protective because I tried to move my project to the "current location" which is Qt project build folder by using -system("copy project_path/xxx.cpp xxx.cpp"); this didn't give an error but said -(0) files are copied. -So I decided to get rid of Qt lol

-Step2: -cd the folder where I put my project in Windows Command Prompt

$cd project_path

-Step3: -compile my own project in Windows Command Prompt

project_path$g++ *.h *.cpp -o execute

compile command: g++ project_path\main.cpp project_path\pair.cpp project_path\map.cpp project_path\pair.h project_path\map.h

(i tried to compile not in its own directory but somehow doesn't work:(( ) ps: inside my project, I have these codes to compile and run the external program:

    void compile(){
    string s = "g++ "
               "project_path\\main.cpp "
               "project_path\\pair.cpp  "
               "project_path\\map.cpp  "                 
               "project_path\\pair.h  "
               "project_path\\map.h";//only this works!!!!

        char *compile_command = new char[s.length()];
        compile_command[0] = '\0';
        strcat(compile_command, s.c_str());
        cout << "compile command: " << compile_command << endl;
        system(compile_command);
    }

-I tried to add "-o execute" to the end of string s but it won't work correctly later. and I tried to set s = "g++ project_path/*.h project_path/*cpp" but it didn't work either:((

    void run(bool input, string input_path){
        if(input){
            string s = "a <" + input_path + "> print.txt";
            char *execute_command = new char[s.length() + 1];
            execute_command[0] = '\0';
            strcat(execute_command, s.c_str());
            system(execute_command);
            cout << "execute_command: " << execute_command << endl;
        }else{
            system("a > print.txt");
        }
    }

    int main(){
        compile();
        run(false, "");
    }

-Step4: -run execute.exe

project_path$execute

then a.exe and print.txt will be seen in the project_folder and print.txt showing correct content.

-I also tried to compile and run for some projects requiring input with input.txt. Works fine too!!!

-I will try the solutions posted above too, later! All explanations are very good! Thank all very much! good day :D