lib/xgetaname-impl.h

   1 /* xgetaname-impl.c -- common implementation of xgethostname and xgetdomainname
   2
   3    Copyright (C) 1992, 1996, 2000-2001, 2003-2006, 2009-2024 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 }