pthreads join problem

I am trying to emulate callback mechanism in C. The code I have is follows:

Code:

---

#include <stdio.h>
#include <pthread.h>

struct fopen_struct {
    char *filename;
    char *mode;
    void *(*callback) (FILE *);
};

void *fopen_callback(FILE *);
pthread_t fopen_t(void *(*callback)(FILE *), const char *, const char *);
void *__fopen_t__(void *);

pthread_t fopen_t(void *(*callback)(FILE *), const char *filename, const char *mode) {
    struct fopen_struct args;
    args.filename = filename;
    args.mode = mode;
    args.callback = callback;
    pthread_t thread;
    pthread_create(&thread, NULL, &__fopen_t__, &args);
    //pthread_join ??
    return thread;
}

void *__fopen_t__(void *ptr) {
    printf("I am done!\n");
    struct fopen_struct *args = (struct fopen_struct *)ptr;
    FILE *result = fopen(args -> filename, args -> mode);
    args -> callback(result);
}

int main() {
    pthread_t thread = fopen_t(&fopen_callback, "test.txt", "r");
    printf("abc\n");
    //pthread_join ??
}

void *fopen_callback(FILE *stream) {
    if (stream != NULL)
        printf("Opened file successfully\n");
    else
        printf("Error\n");
}

---

If I do a pthread_join in fopen_t() it works perfectly fine. But if I do that in main() I get a segmentation fault error. I want to call it in main() because I want it to be non-blocking, is there any solution?

in line 20 you are passing pointer to local var args to pthread_create

you fopen_t could exit before __fopen_t__ will read this memory
as a result __fopen_t__ will access uninitialized memory.

you need to use malloc to allocate args in fopen_t and free it in the __fopen_t__ after the data was read from the struct