lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2020 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 __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 #if defined _WIN32 && ! defined __CYGWIN__
  62 /* Don't assume that UNICODE is not defined.  */
  63 # undef SetEnvironmentVariable
  64 # define SetEnvironmentVariable SetEnvironmentVariableA
  65 #endif
  66
  67 static int
  68 _unsetenv (const char *name)
  69 {
  70   size_t len;
  71 #if !HAVE_DECL__PUTENV
  72   char **ep;
  73 #endif
  74
  75   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  76     {
  77       __set_errno (EINVAL);
  78       return -1;
  79     }
  80
  81   len = strlen (name);
  82
  83 #if HAVE_DECL__PUTENV
  84   {
  85     int putenv_result, putenv_errno;
  86     char *name_ = malloc (len + 2);
  87     memcpy (name_, name, len);
  88     name_[len] = '=';
  89     name_[len + 1] = 0;
  90     putenv_result = _putenv (name_);
  91     putenv_errno = errno;
  92     free (name_);
  93     __set_errno (putenv_errno);
  94     return putenv_result;
  95   }
  96 #else
  97
  98   LOCK;
  99
 100   ep = environ;
 101   while (*ep != NULL)
 102     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 103       {
 104         /* Found it.  Remove this pointer by moving later ones back.  */
 105         char **dp = ep;
 106
 107         do
 108           dp[0] = dp[1];
 109         while (*dp++);
 110         /* Continue the loop in case NAME appears again.  */
 111       }
 112     else
 113       ++ep;
 114
 115   UNLOCK;
 116
 117   return 0;
 118 #endif
 119 }
 120
 121
 122 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
 123    If STRING contains no '=', then remove STRING from the environment.  */
 124 int
 125 putenv (char *string)
 126 {
 127   const char *name_end = strchr (string, '=');
 128   char **ep;
 129
 130   if (name_end == NULL)
 131     {
 132       /* Remove the variable from the environment.  */
 133       return _unsetenv (string);
 134     }
 135
 136 #if HAVE_DECL__PUTENV
 137   /* Rely on _putenv to allocate the new environment.  If other
 138      parts of the application use _putenv, the !HAVE_DECL__PUTENV code
 139      would fight over who owns the environ vector, causing a crash.  */
 140   if (name_end[1])
 141     return _putenv (string);
 142   else
 143     {
 144       /* _putenv ("NAME=") unsets NAME, so invoke _putenv ("NAME= ")
 145          to allocate the environ vector and then replace the new
 146          entry with "NAME=".  */
 147       int putenv_result, putenv_errno;
 148       char *name_x = malloc (name_end - string + sizeof "= ");
 149       if (!name_x)
 150         return -1;
 151       memcpy (name_x, string, name_end - string + 1);
 152       name_x[name_end - string + 1] = ' ';
 153       name_x[name_end - string + 2] = 0;
 154       putenv_result = _putenv (name_x);
 155       putenv_errno = errno;
 156       for (ep = environ; *ep; ep++)
 157         if (strcmp (*ep, name_x) == 0)
 158           {
 159             *ep = string;
 160             break;
 161           }
 162 # if defined _WIN32 && ! defined __CYGWIN__
 163       if (putenv_result == 0)
 164         {
 165           /* _putenv propagated "NAME= " into the subprocess environment;
 166              fix that by calling SetEnvironmentVariable directly.  */
 167           name_x[name_end - string] = 0;
 168           putenv_result = SetEnvironmentVariable (name_x, "") ? 0 : -1;
 169           putenv_errno = ENOMEM; /* ENOMEM is the only way to fail.  */
 170         }
 171 # endif
 172       free (name_x);
 173       __set_errno (putenv_errno);
 174       return putenv_result;
 175     }
 176 #else
 177   for (ep = environ; *ep; ep++)
 178     if (strncmp (*ep, string, name_end - string) == 0
 179         && (*ep)[name_end - string] == '=')
 180       break;
 181
 182   if (*ep)
 183     *ep = string;
 184   else
 185     {
 186       static char **last_environ = NULL;
 187       size_t size = ep - environ;
 188       char **new_environ = malloc ((size + 2) * sizeof *new_environ);
 189       if (! new_environ)
 190         return -1;
 191       new_environ[0] = string;
 192       memcpy (new_environ + 1, environ, (size + 1) * sizeof *new_environ);
 193       free (last_environ);
 194       last_environ = new_environ;
 195       environ = new_environ;
 196     }
 197
 198   return 0;
 199 #endif
 200 }