sysdeps/generic/setenv.c

   1 /* Copyright (C) 1992, 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <errno.h>
  24 #if !_LIBC
  25 # if !defined errno && !defined HAVE_ERRNO_DECL
  26 extern int errno;
  27 # endif
  28 # define __set_errno(ev) ((errno) = (ev))
  29 #endif
  30
  31 #if _LIBC || HAVE_STDLIB_H
  32 # include <stdlib.h>
  33 #endif
  34 #if _LIBC || HAVE_STRING_H
  35 # include <string.h>
  36 #endif
  37 #if _LIBC || HAVE_UNISTD_H
  38 # include <unistd.h>
  39 #endif
  40
  41 #if !_LIBC
  42 # define __environ      environ
  43 # ifndef HAVE_ENVIRON_DECL
  44 extern char **environ;
  45 # endif
  46 #endif
  47
  48 #if _LIBC
  49 /* This lock protects against simultaneous modifications of `environ'.  */
  50 # include <bits/libc-lock.h>
  51 __libc_lock_define_initialized (static, envlock)
  52 # define LOCK   __libc_lock_lock (envlock)
  53 # define UNLOCK __libc_lock_unlock (envlock)
  54 #else
  55 # define LOCK
  56 # define UNLOCK
  57 #endif
  58
  59 /* In the GNU C library we must keep the namespace clean.  */
  60 #ifdef _LIBC
  61 # define setenv __setenv
  62 # define unsetenv __unsetenv
  63 # define clearenv __clearenv
  64 # define tfind __tfind
  65 # define tsearch __tsearch
  66 #endif
  67
  68 /* In the GNU C library implementation we try to be more clever and
  69    allow arbitrary many changes of the environment given that the used
  70    values are from a small set.  Outside glibc this will eat up all
  71    memory after a while.  */
  72 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  73                       && defined __GNUC__)
  74 # define USE_TSEARCH    1
  75 # include <search.h>
  76
  77 /* This is a pointer to the root of the search tree with the known
  78    values.  */
  79 static void *known_values;
  80
  81 # define KNOWN_VALUE(Str) \
  82   ({                                                                          \
  83     void *value = tfind (Str, &known_values, (__compar_fn_t) strcmp);         \
  84     value != NULL ? *(char **) value : NULL;                                  \
  85   })
  86 # define STORE_VALUE(Str) \
  87   tsearch (Str, &known_values, (__compar_fn_t) strcmp)
  88
  89 #else
  90 # undef USE_TSEARCH
  91
  92 # define KNOWN_VALUE(Str) NULL
  93 # define STORE_VALUE(Str) do { } while (0)
  94
  95 #endif
  96
  97
  98 /* If this variable is not a null pointer we allocated the current
  99    environment.  */
 100 static char **last_environ;
 101
 102
 103 int
 104 setenv (name, value, replace)
 105      const char *name;
 106      const char *value;
 107      int replace;
 108 {
 109   register char **ep;
 110   register size_t size;
 111   const size_t namelen = strlen (name);
 112   const size_t vallen = strlen (value) + 1;
 113
 114   LOCK;
 115
 116   size = 0;
 117   if (__environ != NULL)
 118     {
 119       for (ep = __environ; *ep != NULL; ++ep)
 120         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 121           break;
 122         else
 123           ++size;
 124     }
 125
 126   if (__environ == NULL || *ep == NULL)
 127     {
 128       char **new_environ;
 129 #ifdef USE_TSEARCH
 130       char *new_value;
 131 #endif
 132
 133       /* We allocated this space; we can extend it.  */
 134       new_environ = (char **) realloc (last_environ,
 135                                        (size + 2) * sizeof (char *));
 136       if (new_environ == NULL)
 137         {
 138           UNLOCK;
 139           return -1;
 140         }
 141
 142       /* See whether the value is already known.  */
 143 #ifdef USE_TSEARCH
 144       new_value = alloca (namelen + 1 + vallen);
 145 # ifdef _LIBC
 146       __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 147                  value, vallen);
 148 # else
 149       memcpy (new_value, name, namelen);
 150       new_value[namelen] = '=';
 151       memcpy (&new_value[namelen + 1], value, vallen);
 152 # endif
 153
 154       new_environ[size] = KNOWN_VALUE (new_value);
 155       if (new_environ[size] == NULL)
 156 #endif
 157         {
 158           new_environ[size] = malloc (namelen + 1 + vallen);
 159           if (new_environ[size] == NULL)
 160             {
 161               __set_errno (ENOMEM);
 162               UNLOCK;
 163               return -1;
 164             }
 165
 166 #ifdef USE_TSEARCH
 167           memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 168 #else
 169           memcpy (new_environ[size], name, namelen);
 170           new_environ[size][namelen] = '=';
 171           memcpy (&new_environ[size][namelen + 1], value, vallen);
 172 #endif
 173         }
 174
 175       if (__environ != last_environ)
 176         memcpy ((char *) new_environ, (char *) __environ,
 177                 size * sizeof (char *));
 178
 179       new_environ[size + 1] = NULL;
 180
 181       last_environ = __environ = new_environ;
 182     }
 183   else if (replace)
 184     {
 185       char *new_value;
 186       char *np;
 187
 188       /* The existing string is too short; malloc a new one.  */
 189 #ifdef USE_TSEARCH
 190       new_value = alloca (namelen + 1 + vallen);
 191 # ifdef _LIBC
 192       __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 193                  value, vallen);
 194 # else
 195       memcpy (new_value, name, namelen);
 196       new_value[namelen] = '=';
 197       memcpy (&new_value[namelen + 1], value, vallen);
 198 # endif
 199
 200       np = KNOWN_VALUE (new_value);
 201       if (np == NULL)
 202 #endif
 203         {
 204           np = malloc (namelen + 1 + vallen);
 205           if (np == NULL)
 206             {
 207               UNLOCK;
 208               return -1;
 209             }
 210
 211 #ifdef USE_TSEARCH
 212           memcpy (np, new_value, namelen + 1 + vallen);
 213 #else
 214           memcpy (np, name, namelen);
 215           np[namelen] = '=';
 216           memcpy (&np[namelen + 1], value, vallen);
 217 #endif
 218         }
 219
 220       /* Keep the old value around.  */
 221       STORE_VALUE (*ep);
 222       *ep = np;
 223     }
 224
 225   UNLOCK;
 226
 227   return 0;
 228 }
 229
 230 void
 231 unsetenv (name)
 232      const char *name;
 233 {
 234   const size_t len = strlen (name);
 235   char **ep;
 236
 237   LOCK;
 238
 239   for (ep = __environ; *ep != NULL; ++ep)
 240     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 241       {
 242         /* Found it.  Remove this pointer by moving later ones back.  */
 243         char **dp = ep;
 244
 245         /* Store the value so that we can reuse it later.  */
 246         STORE_VALUE (*ep);
 247
 248         do
 249           dp[0] = dp[1];
 250         while (*dp++);
 251         /* Continue the loop in case NAME appears again.  */
 252       }
 253
 254   UNLOCK;
 255 }
 256
 257 /* The `clearenv' was planned to be added to POSIX.1 but probably
 258    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 259    for Fortran 77) requires this function.  */
 260 int
 261 clearenv ()
 262 {
 263   LOCK;
 264
 265   if (__environ == last_environ && __environ != NULL)
 266     {
 267       /* We allocated this environment so we can free it.  Store all the
 268          strings.  */
 269       char **ep = __environ;
 270       while (*ep != NULL)
 271         STORE_VALUE (*ep++);
 272
 273       free (__environ);
 274       last_environ = NULL;
 275     }
 276
 277   /* Clear the environment pointer removes the whole environment.  */
 278   __environ = NULL;
 279
 280   UNLOCK;
 281
 282   return 0;
 283 }
 284 #ifdef _LIBC
 285 # undef setenv
 286 # undef unsetenv
 287 # undef clearenv
 288 weak_alias (__setenv, setenv)
 289 weak_alias (__unsetenv, unsetenv)
 290 weak_alias (__clearenv, clearenv)
 291 #endif