gl/setenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2003,2005-2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
  17
  18 #if !_LIBC
  19 # include <config.h>
  20 #endif
  21 #include <alloca.h>
  22
  23 #include <errno.h>
  24 #ifndef __set_errno
  25 # define __set_errno(ev) ((errno) = (ev))
  26 #endif
  27
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #if _LIBC || HAVE_UNISTD_H
  31 # include <unistd.h>
  32 #endif
  33
  34 #if _LIBC || !HAVE_SETENV
  35
  36 #if !_LIBC
  37 # include "malloca.h"
  38 #endif
  39
  40 #if !_LIBC
  41 # define __environ      environ
  42 # ifndef HAVE_ENVIRON_DECL
  43 extern char **environ;
  44 # endif
  45 #endif
  46
  47 #if _LIBC
  48 /* This lock protects against simultaneous modifications of `environ'.  */
  49 # include <bits/libc-lock.h>
  50 __libc_lock_define_initialized (static, envlock)
  51 # define LOCK   __libc_lock_lock (envlock)
  52 # define UNLOCK __libc_lock_unlock (envlock)
  53 #else
  54 # define LOCK
  55 # define UNLOCK
  56 #endif
  57
  58 /* In the GNU C library we must keep the namespace clean.  */
  59 #ifdef _LIBC
  60 # define setenv __setenv
  61 # define clearenv __clearenv
  62 # define tfind __tfind
  63 # define tsearch __tsearch
  64 #endif
  65
  66 /* In the GNU C library implementation we try to be more clever and
  67    allow arbitrarily many changes of the environment given that the used
  68    values are from a small set.  Outside glibc this will eat up all
  69    memory after a while.  */
  70 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  71                       && defined __GNUC__)
  72 # define USE_TSEARCH    1
  73 # include <search.h>
  74 typedef int (*compar_fn_t) (const void *, const void *);
  75
  76 /* This is a pointer to the root of the search tree with the known
  77    values.  */
  78 static void *known_values;
  79
  80 # define KNOWN_VALUE(Str) \
  81   ({                                                                          \
  82     void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);           \
  83     value != NULL ? *(char **) value : NULL;                                  \
  84   })
  85 # define STORE_VALUE(Str) \
  86   tsearch (Str, &known_values, (compar_fn_t) strcmp)
  87
  88 #else
  89 # undef USE_TSEARCH
  90
  91 # define KNOWN_VALUE(Str) NULL
  92 # define STORE_VALUE(Str) do { } while (0)
  93
  94 #endif
  95
  96
  97 /* If this variable is not a null pointer we allocated the current
  98    environment.  */
  99 static char **last_environ;
 100
 101
 102 /* This function is used by `setenv' and `putenv'.  The difference between
 103    the two functions is that for the former must create a new string which
 104    is then placed in the environment, while the argument of `putenv'
 105    must be used directly.  This is all complicated by the fact that we try
 106    to reuse values once generated for a `setenv' call since we can never
 107    free the strings.  */
 108 int
 109 __add_to_environ (const char *name, const char *value, const char *combined,
 110                   int replace)
 111 {
 112   register char **ep;
 113   register size_t size;
 114   const size_t namelen = strlen (name);
 115   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 116
 117   LOCK;
 118
 119   /* We have to get the pointer now that we have the lock and not earlier
 120      since another thread might have created a new environment.  */
 121   ep = __environ;
 122
 123   size = 0;
 124   if (ep != NULL)
 125     {
 126       for (; *ep != NULL; ++ep)
 127         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 128           break;
 129         else
 130           ++size;
 131     }
 132
 133   if (ep == NULL || *ep == NULL)
 134     {
 135       char **new_environ;
 136 #ifdef USE_TSEARCH
 137       char *new_value;
 138 #endif
 139
 140       /* We allocated this space; we can extend it.  */
 141       new_environ =
 142         (char **) (last_environ == NULL
 143                    ? malloc ((size + 2) * sizeof (char *))
 144                    : realloc (last_environ, (size + 2) * sizeof (char *)));
 145       if (new_environ == NULL)
 146         {
 147           UNLOCK;
 148           return -1;
 149         }
 150
 151       /* If the whole entry is given add it.  */
 152       if (combined != NULL)
 153         /* We must not add the string to the search tree since it belongs
 154            to the user.  */
 155         new_environ[size] = (char *) combined;
 156       else
 157         {
 158           /* See whether the value is already known.  */
 159 #ifdef USE_TSEARCH
 160 # ifdef _LIBC
 161           new_value = (char *) alloca (namelen + 1 + vallen);
 162           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 163                      value, vallen);
 164 # else
 165           new_value = (char *) malloca (namelen + 1 + vallen);
 166           if (new_value == NULL)
 167             {
 168               __set_errno (ENOMEM);
 169               UNLOCK;
 170               return -1;
 171             }
 172           memcpy (new_value, name, namelen);
 173           new_value[namelen] = '=';
 174           memcpy (&new_value[namelen + 1], value, vallen);
 175 # endif
 176
 177           new_environ[size] = KNOWN_VALUE (new_value);
 178           if (new_environ[size] == NULL)
 179 #endif
 180             {
 181               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 182               if (new_environ[size] == NULL)
 183                 {
 184 #if defined USE_TSEARCH && !defined _LIBC
 185                   freea (new_value);
 186 #endif
 187                   __set_errno (ENOMEM);
 188                   UNLOCK;
 189                   return -1;
 190                 }
 191
 192 #ifdef USE_TSEARCH
 193               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 194 #else
 195               memcpy (new_environ[size], name, namelen);
 196               new_environ[size][namelen] = '=';
 197               memcpy (&new_environ[size][namelen + 1], value, vallen);
 198 #endif
 199               /* And save the value now.  We cannot do this when we remove
 200                  the string since then we cannot decide whether it is a
 201                  user string or not.  */
 202               STORE_VALUE (new_environ[size]);
 203             }
 204 #if defined USE_TSEARCH && !defined _LIBC
 205           freea (new_value);
 206 #endif
 207         }
 208
 209       if (__environ != last_environ)
 210         memcpy ((char *) new_environ, (char *) __environ,
 211                 size * sizeof (char *));
 212
 213       new_environ[size + 1] = NULL;
 214
 215       last_environ = __environ = new_environ;
 216     }
 217   else if (replace)
 218     {
 219       char *np;
 220
 221       /* Use the user string if given.  */
 222       if (combined != NULL)
 223         np = (char *) combined;
 224       else
 225         {
 226 #ifdef USE_TSEARCH
 227           char *new_value;
 228 # ifdef _LIBC
 229           new_value = alloca (namelen + 1 + vallen);
 230           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 231                      value, vallen);
 232 # else
 233           new_value = malloca (namelen + 1 + vallen);
 234           if (new_value == NULL)
 235             {
 236               __set_errno (ENOMEM);
 237               UNLOCK;
 238               return -1;
 239             }
 240           memcpy (new_value, name, namelen);
 241           new_value[namelen] = '=';
 242           memcpy (&new_value[namelen + 1], value, vallen);
 243 # endif
 244
 245           np = KNOWN_VALUE (new_value);
 246           if (np == NULL)
 247 #endif
 248             {
 249               np = malloc (namelen + 1 + vallen);
 250               if (np == NULL)
 251                 {
 252 #if defined USE_TSEARCH && !defined _LIBC
 253                   freea (new_value);
 254 #endif
 255                   __set_errno (ENOMEM);
 256                   UNLOCK;
 257                   return -1;
 258                 }
 259
 260 #ifdef USE_TSEARCH
 261               memcpy (np, new_value, namelen + 1 + vallen);
 262 #else
 263               memcpy (np, name, namelen);
 264               np[namelen] = '=';
 265               memcpy (&np[namelen + 1], value, vallen);
 266 #endif
 267               /* And remember the value.  */
 268               STORE_VALUE (np);
 269             }
 270 #if defined USE_TSEARCH && !defined _LIBC
 271           freea (new_value);
 272 #endif
 273         }
 274
 275       *ep = np;
 276     }
 277
 278   UNLOCK;
 279
 280   return 0;
 281 }
 282
 283 int
 284 setenv (const char *name, const char *value, int replace)
 285 {
 286   return __add_to_environ (name, value, NULL, replace);
 287 }
 288
 289 /* The `clearenv' was planned to be added to POSIX.1 but probably
 290    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 291    for Fortran 77) requires this function.  */
 292 int
 293 clearenv (void)
 294 {
 295   LOCK;
 296
 297   if (__environ == last_environ && __environ != NULL)
 298     {
 299       /* We allocated this environment so we can free it.  */
 300       free (__environ);
 301       last_environ = NULL;
 302     }
 303
 304   /* Clear the environment pointer removes the whole environment.  */
 305   __environ = NULL;
 306
 307   UNLOCK;
 308
 309   return 0;
 310 }
 311
 312 #ifdef _LIBC
 313 static void
 314 free_mem (void)
 315 {
 316   /* Remove all traces.  */
 317   clearenv ();
 318
 319   /* Now remove the search tree.  */
 320   __tdestroy (known_values, free);
 321   known_values = NULL;
 322 }
 323 text_set_element (__libc_subfreeres, free_mem);
 324
 325
 326 # undef setenv
 327 # undef clearenv
 328 weak_alias (__setenv, setenv)
 329 weak_alias (__clearenv, clearenv)
 330 #endif
 331
 332 #endif /* _LIBC || !HAVE_SETENV */