Embedding Python to C Segmentation fault-CodePudding

I am trying to track the execution of python scripts with C Threads (If anyone knows a better approach, feel free to mention it)

This is the code I have so far.

#define PY_SSIZE_T_CLEAN
#include </usr/include/python3.8/Python.h>
#include <iostream>
#include <thread>

void launchScript(const char *filename){
    Py_Initialize();
    FILE *fd = fopen(filename, "r");
    PyRun_SimpleFile(fd, filename);
    PyErr_Print();
    Py_Finalize();
 

}
int main(int argc, char const *argv[])
{
    Py_Initialize();
    PyRun_SimpleString("import sys");
    PyRun_SimpleString("sys.path.append(\".\")");
    std::thread first (launchScript,"script.py");
    std::cout << "Thread 1 is running with thread ID: " << first.get_id() << std::endl;
    std::thread second (launchScript,"script2.py");
    std::cout << "Thread 2 is running with thread ID: " << second.get_id() << std::endl;
   
    first.join();
    second.join();
    Py_Finalize();
    return 0; 
   
}

Script.py just has a print statement that prints "Hello World" Script2.py has a print statement that prints "Goodbye World"

I build the application with the following commands

g   -pthread -I/usr/include/python3.8/ main.cpp -L/usr/lib/python3.8/config-3.8-x86_64 linux-gnu -lpython3.8 -o output

When I run ./output, I receive the following on my terminal

Thread 1 is running with thread ID: 140594340370176
Thread 2 is running with thread ID: 140594331977472
GoodBye World
./build.sh: line 2:  7864 Segmentation fault      (core dumped) ./output

I am wondering why I am getting Segmentation Fault. I have tried to debug with PyErr_Print(); but that has not given me any clues.

Any feed back is appreciated.

CodePudding user response：

After testing and debugging the program for about 20 minutes I found that the problem is caused because in your example you've created the second std::thread named second before calling join() on the first thread.

Thus, to solve this just make sure that you've used first.join() before creating the second thread as shown below:

int main(int argc, char const *argv[])
{
    Py_Initialize();
    PyRun_SimpleString("import sys");
    PyRun_SimpleString("sys.path.append(\".\")");
    std::thread first (launchScript,"script.py");
    std::cout << "Thread 1 is running with thread ID: " << first.get_id() << std::endl;
//--vvvvvvvvvvvvv-------->call join on first thread before creating the second std::thread
    first.join();
    
    std::thread second (launchScript,"script2.py");
    std::cout << "Thread 2 is running with thread ID: " << second.get_id() << std::endl;
   
    second.join();
 
    Py_Finalize();
    return 0; 
   
}