Question

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdint.h>
#include <inttypes.h>

typedef struct tmp_num{
    int tmp_1;
    int tmp_2;
}t_num;

/* Dichiarazione prototipi secondo le direttive di pthread */
void *num_mezzo_1(void *num_orig);
void *num_mezzo_2(void *num_orig);

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

    /* Inizializzo i 2 thread */
    pthread_t thread1, thread2;
    int tmp=0,rc1,rc2,num;

    t_num main_tnum;
    num=atoi(argv[1]);
    if(num <= 3){
        printf("Questo è un numero primo: %d\n", num);
        exit(0);
    }
    if( (rc1=pthread_create( &thread1, NULL, &num_mezzo_1, (void *)num)) ){
        printf("Creazione del thread fallita: %d\n", rc1);
        exit(1);
    }
    if( (rc2=pthread_create( &thread2, NULL, &num_mezzo_2, (void *)num)) ){
            printf("Creazione del thread fallita: %d\n", rc2);
            exit(1);
    }
    main_tnum.tmp_1 = 0;
    main_tnum.tmp_2 = 0;
    pthread_join(thread1, (void **)&(main_tnum.tmp_1));
    pthread_join(thread2, (void **)&(main_tnum.tmp_2));
    tmp=main_tnum.tmp_1+main_tnum.tmp_2;
    if(tmp>2){
        printf("Questo NON è un numero primo: %d\n", num);
    }
    else{
        printf("Questo è un numero primo: %d\n", num);
    }
    exit(0);
}

void *num_mezzo_1(void *num_orig){
    t_num p1_tnum;
    int cont_1;
    int n_orig=(int)num_orig;
    p1_tnum.tmp_1 = 0;
    for(cont_1=1; cont_1<=(n_orig/2); cont_1++){
        if((n_orig % cont_1) == 0){
            (p1_tnum.tmp_1)++;
        }
    }
    pthread_exit((void *)(p1_tnum.tmp_1));
    return NULL;
}

void *num_mezzo_2(void *num_orig){
    t_num p2_tnum;
    int cont_2;
    int n_orig=(int)num_orig;
    p2_tnum.tmp_2 = 0;
    for(cont_2=((n_orig/2)+1); cont_2<=n_orig; cont_2++){
        if((n_orig % cont_2) == 0){
            (p2_tnum.tmp_2)++;
        }
    }
    pthread_exit((void *)(p2_tnum.tmp_2));
    return NULL;
}

I’m using Debian Sid 64bit and i have a problem with this simple program that i have developed.
If i compile with clang -Wall -Wextra -o test prime.c -lpthread i got only 1 warn (unused argc) and the program runs fine.
But if i compile it with GCC-4.7.2 (gcc -Wall -Wextra -o test prime.c -lpthread) i got more warns (unused argc + various cast from pointer to integer of different size) and the program fails with a SegFault.
I don’t understand why with clang it works and with GCC it doesn’t.

EDIT:

num_primo_pthread.c: In function ‘main’:
num_primo_pthread.c:33:57: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
num_primo_pthread.c:37:57: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
num_primo_pthread.c:16:14: warning: unused parameter ‘argc’ [-Wunused-parameter]
num_primo_pthread.c: In function ‘num_mezzo_1’:
num_primo_pthread.c:61:13: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
num_primo_pthread.c:68:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
num_primo_pthread.c: In function ‘num_mezzo_2’:
num_primo_pthread.c:75:13: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
num_primo_pthread.c:82:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

Answer 1

the problem lies in this line

int n_orig=(int)num_orig;

num_orig is a pointer to an int, not an int. replace with:

int n_orig=(int)*num_orig;

Edit:

The problem lies a little bit deeper:

(void *)num

you can’t do that, pointers are not used that way, change it to

(void *)&num

Second edit after viewing the errors:

You are doing the same with the return function

(void *)(p2_tnum.tmp_2)

needs to be

(void *)(&p2_tnum.tmp_2)

And this is a local variable so you can’t return it.

t_num p2_tnum

Has to be a pointer with dynamic memory allocated.

t_num *p2_tnum = (t_num *) malloc(sizeof(t_num));

These fixes will require you to do some additional modifications, but I think you can manage those.