C `signal` has too few arguments

Question

I am working on a problem where I am supposed to implement an example of the dining philosopher paradigm. Note: Yes this a homework assignment, before anyone asks.

I am not asking for a solution though. I am confused because this Philosopher function that was supplied below by my teacher is theoretically supposed to work. wait and signal are the function used in C for OS system calls.

I have included them using:

/* Wait and Signal */
#include <signal.h>
#include <sys/wait.h>

struct semaphore
{
    int count = 1;
    struct PCB *Sem_Queue ;
};
struct semaphore Forks[5];

Philosopher()
{
    i = getPID() ;
    while (1)
    {
        think ();
        wait (Forks[i]);
        wait (Forks[(i+1) % 5]);
        eat ();
        signal (Forks[i]);
        signal (Forks[(i + 1) % 5]);
    }
}

However, when compiled I get the error:

Main.c:38:19: error: too few arguments to function call, expected 2, have 1
                signal (Forks[i]);

philosopher needs to be declared properly with return data type — scarecrow-, Dec 07 '16 at 15:08
Have you tried to read the manual for the functions you are trying to use? It helps in most of the cases like this. — Eugene Sh., Dec 07 '16 at 15:09
I tried adding a `void` type to the function but I still get the same errors. — , Dec 07 '16 at 15:09
@EugeneSh. Can you point me in the right direction to the manual? — , Dec 07 '16 at 15:10
apparently signal takes 2 arguments and you're only supplying one — scarecrow-, Dec 07 '16 at 15:10
I have found that it is supposed to take a `sighandler` as a second parameter. I am unsure of what that means though. — , Dec 07 '16 at 15:11
take a look at the prototype definition and it will tell you what type the sighandler is supposed to be — scarecrow-, Dec 07 '16 at 15:12

score 0 · Accepted Answer · answered Dec 07 '16 at 15:23

It appears that the wait() and signal() functions called by Philosopher() are like the think() and eat() functions -- intended to be provided by you (or else included with Philosopher()). The name clash between those and two POSIX functions is unfortunate and confusing, but not meaningful.

Do not include signal.h or sys/wait.h. Instead, provide declarations, by header file or otherwise, for your functions of those names, and make sure your implementations are linked into the executable.

C `signal` has too few arguments

1 Answers1