/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */

#include <pwd.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

/*
 * nonreentrant.c -- demonstrates problems associated with non-reentrant
 *                   functions. Namely, issues that arise when a non-reentrant
 *                   function is interrupted by another function.
 *
 *                   On my machine, however, rather than giving a "getpwnam error",
 *                   the program just gets blocked. Maybe getpwnam uses some kind
 *                   of a lock in its implementation now.
 */

static void my_alarm(int signo)
{
    struct passwd   *rootptr;

    fprintf(stderr, "in signal handler (1)\n");
    if ((rootptr = getpwnam("root")) == NULL)
            fprintf(stderr, "getpwnam(root) error");

    fprintf(stderr, "in signal handler (2)\n");

    alarm(1);
}

int main(void)
{
    struct passwd   *ptr;

    signal(SIGALRM, my_alarm);
    alarm(1);
    for ( ; ; ) {
        if ((ptr = getpwnam("mabdulla")) == NULL)
            fprintf(stderr, "getpwnam error");
        if (strcmp(ptr->pw_name, "mabdulla") != 0)
            fprintf(stderr, "return value corrupted!, pw_name = %s\n", ptr->pw_name);
        fprintf(stderr, ".");
    }

    return 0;
}