lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2018 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 <https://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 #if !HAVE_DECL__PUTENV
  66   char **ep;
  67 #endif
  68
  69   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  70     {
  71       __set_errno (EINVAL);
  72       return -1;
  73     }
  74
  75   len = strlen (name);
  76
  77 #if HAVE_DECL__PUTENV
  78   {
  79     int putenv_result, putenv_errno;
  80     char *name_ = malloc (len + 2);
  81     memcpy (name_, name, len);
  82     name_[len] = '=';
  83     name_[len + 1] = 0;
  84     putenv_result = _putenv (name_);
  85     putenv_errno = errno;
  86     free (name_);
  87     __set_errno (putenv_errno);
  88     return putenv_result;
  89   }
  90 #else
  91
  92   LOCK;
  93
  94   ep = environ;
  95   while (*ep != NULL)
  96     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  97       {
  98         /* Found it.  Remove this pointer by moving later ones back.  */
  99         char **dp = ep;
 100
 101         do
 102           dp[0] = dp[1];
 103         while (*dp++);
 104         /* Continue the loop in case NAME appears again.  */
 105       }
 106     else
 107       ++ep;
 108
 109   UNLOCK;
 110
 111   return 0;
 112 #endif
 113 }
 114
 115
 116 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
 117    If STRING contains no '=', then remove STRING from the environment.  */
 118 int
 119 putenv (char *string)
 120 {
 121   const char *name_end = strchr (string, '=');
 122   char **ep;
 123
 124   if (name_end == NULL)
 125     {
 126       /* Remove the variable from the environment.  */
 127       return _unsetenv (string);
 128     }
 129
 130 #if HAVE_DECL__PUTENV
 131   /* Rely on _putenv to allocate the new environment.  If other
 132      parts of the application use _putenv, the !HAVE_DECL__PUTENV code
 133      would fight over who owns the environ vector, causing a crash.  */
 134   if (name_end[1])
 135     return _putenv (string);
 136   else
 137     {
 138       /* _putenv ("NAME=") unsets NAME, so invoke _putenv ("NAME= ")
 139          to allocate the environ vector and then replace the new
 140          entry with "NAME=".  */
 141       int putenv_result, putenv_errno;
 142       char *name_x = malloc (name_end - string + sizeof "= ");
 143       if (!name_x)
 144         return -1;
 145       memcpy (name_x, string, name_end - string + 1);
 146       name_x[name_end - string + 1] = ' ';
 147       name_x[name_end - string + 2] = 0;
 148       putenv_result = _putenv (name_x);
 149       putenv_errno = errno;
 150       for (ep = environ; *ep; ep++)
 151         if (strcmp (*ep, name_x) == 0)
 152           {
 153             *ep = string;
 154             break;
 155           }
 156 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 157       if (putenv_result == 0)
 158         {
 159           /* _putenv propagated "NAME= " into the subprocess environment;
 160              fix that by calling SetEnvironmentVariable directly.  */
 161           name_x[name_end - string] = 0;
 162           putenv_result = SetEnvironmentVariable (name_x, "") ? 0 : -1;
 163           putenv_errno = ENOMEM; /* ENOMEM is the only way to fail.  */
 164         }
 165 # endif
 166       free (name_x);
 167       __set_errno (putenv_errno);
 168       return putenv_result;
 169     }
 170 #else
 171   for (ep = environ; *ep; ep++)
 172     if (strncmp (*ep, string, name_end - string) == 0
 173         && (*ep)[name_end - string] == '=')
 174       break;
 175
 176   if (*ep)
 177     *ep = string;
 178   else
 179     {
 180       static char **last_environ = NULL;
 181       size_t size = ep - environ;
 182       char **new_environ = malloc ((size + 2) * sizeof *new_environ);
 183       if (! new_environ)
 184         return -1;
 185       new_environ[0] = string;
 186       memcpy (new_environ + 1, environ, (size + 1) * sizeof *new_environ);
 187       free (last_environ);
 188       last_environ = new_environ;
 189       environ = new_environ;
 190     }
 191
 192   return 0;
 193 #endif
 194 }