1  /* Test case for gethostbyname_r bug when buffer expansion required.  */
       2  
       3  #include <netdb.h>
       4  #include <arpa/inet.h>
       5  #include <errno.h>
       6  #include <string.h>
       7  #include <stdio.h>
       8  #include <stdlib.h>
       9  #include <unistd.h>
      10  
      11  int
      12  main (void)
      13  {
      14    const char *host = "www.gnu.org";
      15  
      16    /* This code approximates the example code in the library manual.  */
      17  
      18    struct hostent hostbuf, *hp;
      19    size_t hstbuflen;
      20    char *tmphstbuf;
      21    int res;
      22    int herr;
      23  
      24    hstbuflen = 16;		/* Make it way small to ensure ERANGE.  */
      25    /* Allocate buffer, remember to free it to avoid memory leakage.  */
      26    tmphstbuf = malloc (hstbuflen);
      27  
      28    while ((res = gethostbyname_r (host, &hostbuf, tmphstbuf, hstbuflen,
      29                                   &hp, &herr)) == ERANGE)
      30      {
      31        /* Enlarge the buffer.  */
      32        hstbuflen *= 2;
      33        tmphstbuf = realloc (tmphstbuf, hstbuflen);
      34      }
      35  
      36    if (res != 0 || hp == NULL)
      37      {
      38        printf ("gethostbyname_r failed: %s (errno: %m)\n", strerror (res));
      39  
      40        if (access ("/etc/resolv.conf", R_OK))
      41  	{
      42  	  puts ("DNS probably not set up");
      43  	  return 0;
      44  	}
      45  
      46        return 1;
      47      }
      48  
      49    printf ("Got: %s %s\n", hp->h_name,
      50  	  inet_ntoa (*(struct in_addr *) hp->h_addr));
      51    return 0;
      52  }