root/maint/gnulib/lib/putenv.c

/* */

DEFINITIONS

1. _unsetenv
2. putenv

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2021 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 file is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU Lesser General Public License as
   9    published by the Free Software Foundation; either version 3 of the
  10    License, or (at your option) any later version.
  11 
  12    This file 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 Lesser General Public License for more details.
  16 
  17    You should have received a copy of the GNU Lesser 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;
  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     free (name_);
  92     return putenv_result;
  93   }
  94 #else
  95 
  96   LOCK;
  97 
  98   ep = environ;
  99   while (*ep != NULL)
 100     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 101       {
 102         /* Found it.  Remove this pointer by moving later ones back.  */
 103         char **dp = ep;
 104 
 105         do
 106           dp[0] = dp[1];
 107         while (*dp++);
 108         /* Continue the loop in case NAME appears again.  */
 109       }
 110     else
 111       ++ep;
 112 
 113   UNLOCK;
 114 
 115   return 0;
 116 #endif
 117 }
 118 
 119 
 120 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
 121    If STRING contains no '=', then remove STRING from the environment.  */
 122 int
 123 putenv (char *string)
     /*  */
 124 {
 125   const char *name_end = strchr (string, '=');
 126   char **ep;
 127 
 128   if (name_end == NULL)
 129     {
 130       /* Remove the variable from the environment.  */
 131       return _unsetenv (string);
 132     }
 133 
 134 #if HAVE_DECL__PUTENV
 135   /* Rely on _putenv to allocate the new environment.  If other
 136      parts of the application use _putenv, the !HAVE_DECL__PUTENV code
 137      would fight over who owns the environ vector, causing a crash.  */
 138   if (name_end[1])
 139     return _putenv (string);
 140   else
 141     {
 142       /* _putenv ("NAME=") unsets NAME, so invoke _putenv ("NAME= ")
 143          to allocate the environ vector and then replace the new
 144          entry with "NAME=".  */
 145       int putenv_result;
 146       char *name_x = malloc (name_end - string + sizeof "= ");
 147       if (!name_x)
 148         return -1;
 149       memcpy (name_x, string, name_end - string + 1);
 150       name_x[name_end - string + 1] = ' ';
 151       name_x[name_end - string + 2] = 0;
 152       putenv_result = _putenv (name_x);
 153       for (ep = environ; *ep; ep++)
 154         if (strcmp (*ep, name_x) == 0)
 155           {
 156             *ep = string;
 157             break;
 158           }
 159 # if defined _WIN32 && ! defined __CYGWIN__
 160       if (putenv_result == 0)
 161         {
 162           /* _putenv propagated "NAME= " into the subprocess environment;
 163              fix that by calling SetEnvironmentVariable directly.  */
 164           name_x[name_end - string] = 0;
 165           putenv_result = SetEnvironmentVariable (name_x, "") ? 0 : -1;
 166           errno = ENOMEM; /* ENOMEM is the only way to fail.  */
 167         }
 168 # endif
 169       free (name_x);
 170       return putenv_result;
 171     }
 172 #else
 173   for (ep = environ; *ep; ep++)
 174     if (strncmp (*ep, string, name_end - string) == 0
 175         && (*ep)[name_end - string] == '=')
 176       break;
 177 
 178   if (*ep)
 179     *ep = string;
 180   else
 181     {
 182       static char **last_environ = NULL;
 183       size_t size = ep - environ;
 184       char **new_environ = malloc ((size + 2) * sizeof *new_environ);
 185       if (! new_environ)
 186         return -1;
 187       new_environ[0] = string;
 188       memcpy (new_environ + 1, environ, (size + 1) * sizeof *new_environ);
 189       free (last_environ);
 190       last_environ = new_environ;
 191       environ = new_environ;
 192     }
 193 
 194   return 0;
 195 #endif
 196 }

/* */