Question

I have the following Main program:

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

    /*checkParameters(argc,argv);*/

    if (pthread_create(&supplierid, NULL, &supplier, NULL) != 0);
        error("ERROR creating supply threads \n");

}

void *supplier () {

    printf("hello? \n"); 

    while (timeremaining >= 0) {


        printf("\n the stock is %d" , stock);
        printf("\n the supply ies %d", supply);

        timeremaining--;

        if (stock + supply > cap_max)
            stock = cap_max;
        else
            stock = stock + supply;

        sleep(0.1);
    }

    exit(EXIT_SUCCESS);
}

Ok well, 95% of the time I run this program I get Error creating supply thread. And it never prints hello.
This makes no sense. It just 1 thread.

thanks in advance.

Answer 1

You have a semicolon after your if statement:

if (pthread_create(&supplierid, NULL, &supplier, NULL) != 0);

This means that the statement that appears to be nested within the if statement is not actually nested at all and will always execute regardless of the condition. Specifically, C is interpreting your code to mean

if (pthread_create(&supplierid, NULL, &supplier, NULL) != 0)
    ; /* Do nothing */

error("ERROR creating supply threads \n");

To fix this, remove the stray semicolon.

Hope this helps!