stdlib/setenv.c

   1 /* Copyright (C) 1992,1995-2001,2004 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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 arbitrarily 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 /* This function is used by `setenv' and `putenv'.  The difference between
 104    the two functions is that for the former must create a new string which
 105    is then placed in the environment, while the argument of `putenv'
 106    must be used directly.  This is all complicated by the fact that we try
 107    to reuse values once generated for a `setenv' call since we can never
 108    free the strings.  */
 109 int
 110 __add_to_environ (name, value, combined, replace)
 111      const char *name;
 112      const char *value;
 113      const char *combined;
 114      int replace;
 115 {
 116   register char **ep;
 117   register size_t size;
 118   const size_t namelen = strlen (name);
 119   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 120
 121   LOCK;
 122
 123   /* We have to get the pointer now that we have the lock and not earlier
 124      since another thread might have created a new environment.  */
 125   ep = __environ;
 126
 127   size = 0;
 128   if (ep != NULL)
 129     {
 130       for (; *ep != NULL; ++ep)
 131         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 132           break;
 133         else
 134           ++size;
 135     }
 136
 137   if (ep == NULL || __builtin_expect (*ep == NULL, 1))
 138     {
 139       char **new_environ;
 140
 141       /* We allocated this space; we can extend it.  */
 142       new_environ = (char **) realloc (last_environ,
 143                                        (size + 2) * sizeof (char *));
 144       if (new_environ == NULL)
 145         {
 146           UNLOCK;
 147           return -1;
 148         }
 149
 150       /* If the whole entry is given add it.  */
 151       if (combined != NULL)
 152         /* We must not add the string to the search tree since it belongs
 153            to the user.  */
 154         new_environ[size] = (char *) combined;
 155       else
 156         {
 157           /* See whether the value is already known.  */
 158 #ifdef USE_TSEARCH
 159 # ifdef __GNUC__
 160           char new_value[namelen + 1 + vallen];
 161 # else
 162           char *new_value = (char *) alloca (namelen + 1 + vallen);
 163 # endif
 164 # ifdef _LIBC
 165           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 166                      value, vallen);
 167 # else
 168           memcpy (new_value, name, namelen);
 169           new_value[namelen] = '=';
 170           memcpy (&new_value[namelen + 1], value, vallen);
 171 # endif
 172
 173           new_environ[size] = KNOWN_VALUE (new_value);
 174           if (__builtin_expect (new_environ[size] == NULL, 1))
 175 #endif
 176             {
 177               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 178               if (__builtin_expect (new_environ[size] == NULL, 0))
 179                 {
 180                   __set_errno (ENOMEM);
 181                   UNLOCK;
 182                   return -1;
 183                 }
 184
 185 #ifdef USE_TSEARCH
 186               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 187 #else
 188               memcpy (new_environ[size], name, namelen);
 189               new_environ[size][namelen] = '=';
 190               memcpy (&new_environ[size][namelen + 1], value, vallen);
 191 #endif
 192               /* And save the value now.  We cannot do this when we remove
 193                  the string since then we cannot decide whether it is a
 194                  user string or not.  */
 195               STORE_VALUE (new_environ[size]);
 196             }
 197         }
 198
 199       if (__environ != last_environ)
 200         memcpy ((char *) new_environ, (char *) __environ,
 201                 size * sizeof (char *));
 202
 203       new_environ[size + 1] = NULL;
 204
 205       last_environ = __environ = new_environ;
 206     }
 207   else if (replace)
 208     {
 209       char *np;
 210
 211       /* Use the user string if given.  */
 212       if (combined != NULL)
 213         np = (char *) combined;
 214       else
 215         {
 216 #ifdef USE_TSEARCH
 217 # ifdef __GNUC__
 218           char new_value[namelen + 1 + vallen];
 219 # else
 220           char *new_value = (char *) alloca (namelen + 1 + vallen);
 221 # endif
 222 # ifdef _LIBC
 223           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 224                      value, vallen);
 225 # else
 226           memcpy (new_value, name, namelen);
 227           new_value[namelen] = '=';
 228           memcpy (&new_value[namelen + 1], value, vallen);
 229 # endif
 230
 231           np = KNOWN_VALUE (new_value);
 232           if (__builtin_expect (np == NULL, 1))
 233 #endif
 234             {
 235               np = malloc (namelen + 1 + vallen);
 236               if (__builtin_expect (np == NULL, 0))
 237                 {
 238                   UNLOCK;
 239                   return -1;
 240                 }
 241
 242 #ifdef USE_TSEARCH
 243               memcpy (np, new_value, namelen + 1 + vallen);
 244 #else
 245               memcpy (np, name, namelen);
 246               np[namelen] = '=';
 247               memcpy (&np[namelen + 1], value, vallen);
 248 #endif
 249               /* And remember the value.  */
 250               STORE_VALUE (np);
 251             }
 252         }
 253
 254       *ep = np;
 255     }
 256
 257   UNLOCK;
 258
 259   return 0;
 260 }
 261
 262 int
 263 setenv (name, value, replace)
 264      const char *name;
 265      const char *value;
 266      int replace;
 267 {
 268   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 269     {
 270       __set_errno (EINVAL);
 271       return -1;
 272     }
 273
 274   return __add_to_environ (name, value, NULL, replace);
 275 }
 276
 277 int
 278 unsetenv (name)
 279      const char *name;
 280 {
 281   size_t len;
 282   char **ep;
 283
 284   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 285     {
 286       __set_errno (EINVAL);
 287       return -1;
 288     }
 289
 290   len = strlen (name);
 291
 292   LOCK;
 293
 294   ep = __environ;
 295   while (*ep != NULL)
 296     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 297       {
 298         /* Found it.  Remove this pointer by moving later ones back.  */
 299         char **dp = ep;
 300
 301         do
 302           dp[0] = dp[1];
 303         while (*dp++);
 304         /* Continue the loop in case NAME appears again.  */
 305       }
 306     else
 307       ++ep;
 308
 309   UNLOCK;
 310
 311   return 0;
 312 }
 313
 314 /* The `clearenv' was planned to be added to POSIX.1 but probably
 315    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 316    for Fortran 77) requires this function.  */
 317 int
 318 clearenv ()
 319 {
 320   LOCK;
 321
 322   if (__environ == last_environ && __environ != NULL)
 323     {
 324       /* We allocated this environment so we can free it.  */
 325       free (__environ);
 326       last_environ = NULL;
 327     }
 328
 329   /* Clear the environment pointer removes the whole environment.  */
 330   __environ = NULL;
 331
 332   UNLOCK;
 333
 334   return 0;
 335 }
 336 #ifdef _LIBC
 337 libc_freeres_fn (free_mem)
 338 {
 339   /* Remove all traces.  */
 340   clearenv ();
 341
 342   /* Now remove the search tree.  */
 343   __tdestroy (known_values, free);
 344   known_values = NULL;
 345 }
 346
 347 # undef setenv
 348 # undef unsetenv
 349 # undef clearenv
 350 weak_alias (__setenv, setenv)
 351 weak_alias (__unsetenv, unsetenv)
 352 weak_alias (__clearenv, clearenv)
 353 #endif