1  /* xgetaname-impl.c -- common implementation of xgethostname and xgetdomainname
       2  
       3     Copyright (C) 1992, 1996, 2000-2001, 2003-2006, 2009-2023 Free Software
       4     Foundation, Inc.
       5  
       6     This program is free software: you can redistribute it and/or modify
       7     it under the terms of the GNU General Public License as published by
       8     the Free Software Foundation, either version 3 of the License, or
       9     (at your option) any later version.
      10  
      11     This program is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14     GNU General Public License for more details.
      15  
      16     You should have received a copy of the GNU General Public License
      17     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      18  
      19  /* written by Jim Meyering and Paul Eggert */
      20  
      21  #include <stdlib.h>
      22  #include <errno.h>
      23  #include <string.h>
      24  #include <unistd.h>
      25  
      26  #include "xalloc.h"
      27  
      28  /* Return the current host or domain name in malloc'd storage.
      29     If malloc fails, exit.
      30     Upon any other failure, return NULL and set errno.  */
      31  char *
      32  XGETANAME (void)
      33  {
      34    char buf[100];
      35    idx_t size = sizeof buf;
      36    char *name = buf;
      37    char *alloc = NULL;
      38  
      39    while (1)
      40      {
      41        /* Use SIZE_1 here rather than SIZE to work around the bug in
      42           SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
      43           even when the name is as long as the supplied buffer.  */
      44        idx_t size_1 = size - 1;
      45        name[size_1] = '\0';
      46        errno = 0;
      47        if (GETANAME (name, size_1) == 0)
      48          {
      49            /* Check whether the name was possibly truncated; POSIX does not
      50               specify whether a truncated name is null-terminated.  */
      51            idx_t actual_size = strlen (name) + 1;
      52            if (actual_size < size_1)
      53              return alloc ? alloc : ximemdup (name, actual_size);
      54            errno = 0;
      55          }
      56        free (alloc);
      57        if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
      58            /* macOS/Darwin does this when SIZE_1 is too small.  */
      59            && errno != ENOMEM)
      60          return NULL;
      61        name = alloc = xpalloc (NULL, &size, 1, -1, 1);
      62      }
      63  }