implementing Using `pthread_create` and Thread-Safety in C on Ubuntu 20.04
I'm having trouble with I'm integrating two systems and I'm working on a multi-threaded application in C on Ubuntu 20.04, and I'm working with a segmentation fault when I try to create threads using `pthread_create`. The application is expected to perform some concurrent file processing, and I suspect that there might be an scenario with thread safety when accessing shared resources. Here’s the relevant part of my code: ```c #include <stdio.h> #include <stdlib.h> #include <pthread.h> #define NUM_THREADS 5 void *processFile(void *threadid) { long tid = (long)threadid; printf("Thread %ld: Processing file...\n", tid); // Simulate some processing return NULL; } int main() { pthread_t threads[NUM_THREADS]; int rc; long t; for(t = 0; t < NUM_THREADS; t++) { rc = pthread_create(&threads[t], NULL, processFile, (void *)t); if (rc) { printf("behavior; return code from pthread_create() is %d\n", rc); exit(-1); } } // Wait for all threads to complete for(t = 0; t < NUM_THREADS; t++) { pthread_join(threads[t], NULL); } return 0; } ``` When I run this code, I get a segmentation fault, and it appears to happen intermittently. I’ve tried adding `pthread_join` after creating each thread, but that causes the program to deadlock as it waits for a thread that hasn’t been created yet. I suspect that the scenario might relate to how I’m passing the thread ID to the thread function. Since I'm using a loop variable, is there a risk of it being overwritten before the thread accesses it? I’ve read that using a pointer to a local variable can lead to undefined behavior. Also, I’m passing the thread ID as `void *` which should work, but could this be causing any alignment issues or pointer truncation on my system? I would appreciate any insights on how to ensure thread safety and avoid this segmentation fault, as well as best practices for managing thread IDs in a multi-threaded context. Thanks! Am I missing something obvious? This is my first time working with C stable. This issue appeared after updating to C stable. Has anyone dealt with something similar? I'm on Debian using the latest version of C. Is this even possible?