/* desc.c - function descriptors vs code addresses; where errno really is. C89. */
#include <stdio.h>
#include <errno.h>
#include <pthread.h>
#include <unistd.h>
static void *tfn(void *a) { printf("errno in thread   %p\n", (void *)&errno); return 0; }
int main(void)
{
    unsigned long *d;
    pthread_t t;
    setvbuf(stdout, 0, _IONBF, 0);
    d = (unsigned long *)main;   printf("main desc %p -> code %08lx toc %08lx\n", (void *)d, d[0], d[1]);
    d = (unsigned long *)printf; printf("printf desc %p -> code %08lx toc %08lx\n", (void *)d, d[0], d[1]);
    d = (unsigned long *)getpid; printf("getpid desc %p -> code %08lx toc %08lx\n", (void *)d, d[0], d[1]);
    printf("errno in main     %p\n", (void *)&errno);
    pthread_create(&t, 0, tfn, 0); pthread_join(t, 0);
    return 0;
}