lib/setenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2003 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21 #include <alloca.h>
  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 #include <stdlib.h>
  32 #include <string.h>
  33 #if _LIBC || HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36
  37 /* For those losing systems which don't have 'alloca' we have to add
  38    some additional code emulating it.  */
  39 #if _LIBC || HAVE_ALLOCA
  40 # define freea(p) /* nothing */
  41 #else
  42 # define alloca(n) malloc (n)
  43 # define freea(p) free (p)
  44 #endif
  45
  46 #if !_LIBC
  47 # define __environ      environ
  48 # ifndef HAVE_ENVIRON_DECL
  49 extern char **environ;
  50 # endif
  51 #endif
  52
  53 #if _LIBC
  54 /* This lock protects against simultaneous modifications of `environ'.  */
  55 # include <bits/libc-lock.h>
  56 __libc_lock_define_initialized (static, envlock)
  57 # define LOCK   __libc_lock_lock (envlock)
  58 # define UNLOCK __libc_lock_unlock (envlock)
  59 #else
  60 # define LOCK
  61 # define UNLOCK
  62 #endif
  63
  64 /* In the GNU C library we must keep the namespace clean.  */
  65 #ifdef _LIBC
  66 # define setenv __setenv
  67 # define clearenv __clearenv
  68 # define tfind __tfind
  69 # define tsearch __tsearch
  70 #endif
  71
  72 /* In the GNU C library implementation we try to be more clever and
  73    allow arbitrarily many changes of the environment given that the used
  74    values are from a small set.  Outside glibc this will eat up all
  75    memory after a while.  */
  76 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  77                       && defined __GNUC__)
  78 # define USE_TSEARCH    1
  79 # include <search.h>
  80 typedef int (*compar_fn_t) (const void *, const void *);
  81
  82 /* This is a pointer to the root of the search tree with the known
  83    values.  */
  84 static void *known_values;
  85
  86 # define KNOWN_VALUE(Str) \
  87   ({                                                                          \
  88     void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);           \
  89     value != NULL ? *(char **) value : NULL;                                  \
  90   })
  91 # define STORE_VALUE(Str) \
  92   tsearch (Str, &known_values, (compar_fn_t) strcmp)
  93
  94 #else
  95 # undef USE_TSEARCH
  96
  97 # define KNOWN_VALUE(Str) NULL
  98 # define STORE_VALUE(Str) do { } while (0)
  99
 100 #endif
 101
 102
 103 /* If this variable is not a null pointer we allocated the current
 104    environment.  */
 105 static char **last_environ;
 106
 107
 108 /* This function is used by `setenv' and `putenv'.  The difference between
 109    the two functions is that for the former must create a new string which
 110    is then placed in the environment, while the argument of `putenv'
 111    must be used directly.  This is all complicated by the fact that we try
 112    to reuse values once generated for a `setenv' call since we can never
 113    free the strings.  */
 114 int
 115 __add_to_environ (const char *name, const char *value, const char *combined,
 116                   int replace)
 117 {
 118   register char **ep;
 119   register size_t size;
 120   const size_t namelen = strlen (name);
 121   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 122
 123   LOCK;
 124
 125   /* We have to get the pointer now that we have the lock and not earlier
 126      since another thread might have created a new environment.  */
 127   ep = __environ;
 128
 129   size = 0;
 130   if (ep != NULL)
 131     {
 132       for (; *ep != NULL; ++ep)
 133         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 134           break;
 135         else
 136           ++size;
 137     }
 138
 139   if (ep == NULL || *ep == NULL)
 140     {
 141       char **new_environ;
 142 #ifdef USE_TSEARCH
 143       char *new_value;
 144 #endif
 145
 146       /* We allocated this space; we can extend it.  */
 147       new_environ =
 148         (char **) (last_environ == NULL
 149                    ? malloc ((size + 2) * sizeof (char *))
 150                    : realloc (last_environ, (size + 2) * sizeof (char *)));
 151       if (new_environ == NULL)
 152         {
 153           UNLOCK;
 154           return -1;
 155         }
 156
 157       /* If the whole entry is given add it.  */
 158       if (combined != NULL)
 159         /* We must not add the string to the search tree since it belongs
 160            to the user.  */
 161         new_environ[size] = (char *) combined;
 162       else
 163         {
 164           /* See whether the value is already known.  */
 165 #ifdef USE_TSEARCH
 166           new_value = (char *) alloca (namelen + 1 + vallen);
 167 # ifdef _LIBC
 168           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 169                      value, vallen);
 170 # else
 171           memcpy (new_value, name, namelen);
 172           new_value[namelen] = '=';
 173           memcpy (&new_value[namelen + 1], value, vallen);
 174 # endif
 175
 176           new_environ[size] = KNOWN_VALUE (new_value);
 177           if (new_environ[size] == NULL)
 178 #endif
 179             {
 180               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 181               if (new_environ[size] == NULL)
 182                 {
 183 #ifdef USE_TSEARCH
 184                   freea (new_value);
 185 #endif
 186                   __set_errno (ENOMEM);
 187                   UNLOCK;
 188                   return -1;
 189                 }
 190
 191 #ifdef USE_TSEARCH
 192               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 193 #else
 194               memcpy (new_environ[size], name, namelen);
 195               new_environ[size][namelen] = '=';
 196               memcpy (&new_environ[size][namelen + 1], value, vallen);
 197 #endif
 198               /* And save the value now.  We cannot do this when we remove
 199                  the string since then we cannot decide whether it is a
 200                  user string or not.  */
 201               STORE_VALUE (new_environ[size]);
 202             }
 203 #ifdef USE_TSEARCH
 204           freea (new_value);
 205 #endif
 206         }
 207
 208       if (__environ != last_environ)
 209         memcpy ((char *) new_environ, (char *) __environ,
 210                 size * sizeof (char *));
 211
 212       new_environ[size + 1] = NULL;
 213
 214       last_environ = __environ = new_environ;
 215     }
 216   else if (replace)
 217     {
 218       char *np;
 219
 220       /* Use the user string if given.  */
 221       if (combined != NULL)
 222         np = (char *) combined;
 223       else
 224         {
 225 #ifdef USE_TSEARCH
 226           char *new_value = alloca (namelen + 1 + vallen);
 227 # ifdef _LIBC
 228           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 229                      value, vallen);
 230 # else
 231           memcpy (new_value, name, namelen);
 232           new_value[namelen] = '=';
 233           memcpy (&new_value[namelen + 1], value, vallen);
 234 # endif
 235
 236           np = KNOWN_VALUE (new_value);
 237           if (np == NULL)
 238 #endif
 239             {
 240               np = malloc (namelen + 1 + vallen);
 241               if (np == NULL)
 242                 {
 243 #ifdef USE_TSEARCH
 244                   freea (new_value);
 245 #endif
 246                   UNLOCK;
 247                   return -1;
 248                 }
 249
 250 #ifdef USE_TSEARCH
 251               memcpy (np, new_value, namelen + 1 + vallen);
 252 #else
 253               memcpy (np, name, namelen);
 254               np[namelen] = '=';
 255               memcpy (&np[namelen + 1], value, vallen);
 256 #endif
 257               /* And remember the value.  */
 258               STORE_VALUE (np);
 259             }
 260 #ifdef USE_TSEARCH
 261           freea (new_value);
 262 #endif
 263         }
 264
 265       *ep = np;
 266     }
 267
 268   UNLOCK;
 269
 270   return 0;
 271 }
 272
 273 int
 274 setenv (const char *name, const char *value, int replace)
 275 {
 276   return __add_to_environ (name, value, NULL, replace);
 277 }
 278
 279 /* The `clearenv' was planned to be added to POSIX.1 but probably
 280    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 281    for Fortran 77) requires this function.  */
 282 int
 283 clearenv (void)
 284 {
 285   LOCK;
 286
 287   if (__environ == last_environ && __environ != NULL)
 288     {
 289       /* We allocated this environment so we can free it.  */
 290       free (__environ);
 291       last_environ = NULL;
 292     }
 293
 294   /* Clear the environment pointer removes the whole environment.  */
 295   __environ = NULL;
 296
 297   UNLOCK;
 298
 299   return 0;
 300 }
 301
 302 #ifdef _LIBC
 303 static void
 304 free_mem (void)
 305 {
 306   /* Remove all traces.  */
 307   clearenv ();
 308
 309   /* Now remove the search tree.  */
 310   __tdestroy (known_values, free);
 311   known_values = NULL;
 312 }
 313 text_set_element (__libc_subfreeres, free_mem);
 314
 315
 316 # undef setenv
 317 # undef clearenv
 318 weak_alias (__setenv, setenv)
 319 weak_alias (__clearenv, clearenv)
 320 #endif