CODEWITHSUNDEEP
cmultithreadingposix
plaknas
plaknas

Reputation: 274

Runtime error- POSIX threads

I am trying to create threads with the pthread library. Compilation is fine with gcc -o -pthread file file.c

but when I run the code, I get a segmentation fault. I am not sure what the problem is. I tried to execute the code that was given in the textbook to try and learn but I am lost right now. Can anyone help? The code is below... very basic, yes but please hlep me out.

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

int sum;
void *runner(void *param);

int main (int argc, char *argv[])
{
    pthread_t tid;
    pthread_attr_t attr;
    //printf("Am I here..?\n");
    if (argc!=2)
    {
        fprintf(stderr, "usage: a.out ...\n");
        return -1;
    }

    if (atoi(argv[1] < 0))
    {
        fprintf(stderr, "%d must be >= 0\n", atoi(argv[1]));
        return -1;
    }



    pthread_attr_init(&attr);
    pthread_create(&tid, &attr, runner, argv[1]);
    pthread_join(tid, NULL);

    printf("sum = %d\n", sum);
}

void *runner(void *param)
{
    extern int sum;
    int i, upper=atoi(param);
    sum=0;

    for(i=1; i<= upper; i++)
        sum+=i;

    pthread_exit(0);
}

Upvotes: 0

Views: 162

Answers (2)

Mat
Mat

Reputation: 206899

Please turn on, and examine carefully, your compiler's warnings.

You're not including stdlib.h, so atoi is undeclared, and you're not returning anything from runner but you've declared it as returning a void*.

But the main problem is this line:

if (atoi(argv[1] < 0))

argv[1] < 0 will evaluate to 0 or 1, which are not what you want as an argument to atoi. What you wanted is:

if (atoi(argv[1]) < 0)

It's more than likely that your compiler would have indicated all these problems if the right warnings were enabled.

Upvotes: 3

P.P
P.P

Reputation: 121427

You have misplaced the bracket:

Change: 

if (atoi(argv[1] < 0))

to: 

if (atoi(argv[1]) < 0)

Upvotes: 1

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