code.delx.au - gnu-emacs/blob - lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2013 Free Software
   2    Foundation, Inc.
   3
   4    NOTE: The canonical source of this file is maintained with the GNU C
   5    Library.  Bugs can be reported to bug-glibc@prep.ai.mit.edu.
   6
   7    This program is free software: you can redistribute it and/or modify it
   8    under the terms of the GNU General Public License as published by the
   9    Free Software Foundation; either version 3 of the License, or any
  10    later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <stdlib.h>
  24
  25 #include <stddef.h>
  26
  27 /* Include errno.h *after* sys/types.h to work around header problems
  28    on AIX 3.2.5.  */
  29 #include <errno.h>
  30 #ifndef __set_errno
  31 # define __set_errno(ev) ((errno) = (ev))
  32 #endif
  33
  34 #include <string.h>
  35 #include <unistd.h>
  36
  37 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  38 # define WIN32_LEAN_AND_MEAN
  39 # include <windows.h>
  40 #endif
  41
  42 #if _LIBC
  43 # if HAVE_GNU_LD
  44 #  define environ __environ
  45 # else
  46 extern char **environ;
  47 # endif
  48 #endif
  49
  50 #if _LIBC
  51 /* This lock protects against simultaneous modifications of 'environ'.  */
  52 # include <bits/libc-lock.h>
  53 __libc_lock_define_initialized (static, envlock)
  54 # define LOCK   __libc_lock_lock (envlock)
  55 # define UNLOCK __libc_lock_unlock (envlock)
  56 #else
  57 # define LOCK
  58 # define UNLOCK
  59 #endif
  60
  61 static int
  62 _unsetenv (const char *name)
  63 {
  64   size_t len;
  65   char **ep;
  66
  67   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  68     {
  69       __set_errno (EINVAL);
  70       return -1;
  71     }
  72
  73   len = strlen (name);
  74
  75 #if HAVE__PUTENV
  76   {
  77     int putenv_result, putenv_errno;
  78     char *name_ = malloc (len + 2);
  79     memcpy (name_, name, len);
  80     name_[len] = '=';
  81     name_[len + 1] = 0;
  82     putenv_result = _putenv (name_);
  83     putenv_errno = errno;
  84     free (name_);
  85     __set_errno (putenv_errno);
  86     return putenv_result;
  87   }
  88 #else
  89
  90   LOCK;
  91
  92   ep = environ;
  93   while (*ep != NULL)
  94     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  95       {
  96         /* Found it.  Remove this pointer by moving later ones back.  */
  97         char **dp = ep;
  98
  99         do
 100           dp[0] = dp[1];
 101         while (*dp++);
 102         /* Continue the loop in case NAME appears again.  */
 103       }
 104     else
 105       ++ep;
 106
 107   UNLOCK;
 108
 109   return 0;
 110 #endif
 111 }
 112
 113
 114 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
 115    If STRING contains no '=', then remove STRING from the environment.  */
 116 int
 117 putenv (char *string)
 118 {
 119   const char *name_end = strchr (string, '=');
 120   char **ep;
 121
 122   if (name_end == NULL)
 123     {
 124       /* Remove the variable from the environment.  */
 125       return _unsetenv (string);
 126     }
 127
 128 #if HAVE__PUTENV
 129       /* Rely on _putenv to allocate the new environment.  If other
 130          parts of the application use _putenv, the !HAVE__PUTENV code
 131          would fight over who owns the environ vector, causing a crash.  */
 132       if (name_end[1])
 133         return _putenv (string);
 134       else
 135         {
 136           /* _putenv ("NAME=") unsets NAME, so invoke _putenv ("NAME= ")
 137              to allocate the environ vector and then replace the new
 138              entry with "NAME=".  */
 139           int putenv_result, putenv_errno;
 140           char *name_x = malloc (name_end - string + sizeof "= ");
 141           if (!name_x)
 142             return -1;
 143           memcpy (name_x, string, name_end - string + 1);
 144           name_x[name_end - string + 1] = ' ';
 145           name_x[name_end - string + 2] = 0;
 146           putenv_result = _putenv (name_x);
 147           putenv_errno = errno;
 148           for (ep = environ; *ep; ep++)
 149             if (strcmp (*ep, name_x) == 0)
 150               {
 151                 *ep = string;
 152                 break;
 153               }
 154 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 155           if (putenv_result == 0)
 156             {
 157               /* _putenv propagated "NAME= " into the subprocess environment;
 158                  fix that by calling SetEnvironmentVariable directly.  */
 159               name_x[name_end - string] = 0;
 160               putenv_result = SetEnvironmentVariable (name_x, "") ? 0 : -1;
 161               putenv_errno = ENOMEM; /* ENOMEM is the only way to fail.  */
 162             }
 163 # endif
 164           free (name_x);
 165           __set_errno (putenv_errno);
 166           return putenv_result;
 167         }
 168 #else
 169   for (ep = environ; *ep; ep++)
 170     if (strncmp (*ep, string, name_end - string) == 0
 171         && (*ep)[name_end - string] == '=')
 172       break;
 173
 174   if (*ep)
 175     *ep = string;
 176   else
 177     {
 178       static char **last_environ = NULL;
 179       size_t size = ep - environ;
 180       char **new_environ = malloc ((size + 2) * sizeof *new_environ);
 181       if (! new_environ)
 182         return -1;
 183       new_environ[0] = string;
 184       memcpy (new_environ + 1, environ, (size + 1) * sizeof *new_environ);
 185       free (last_environ);
 186       last_environ = new_environ;
 187       environ = new_environ;
 188     }
 189 #endif
 190
 191   return 0;
 192 }