stdlib/setenv.c

   1 /* Copyright (C) 1992-2014 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <errno.h>
  23 #if !_LIBC
  24 # if !defined errno && !defined HAVE_ERRNO_DECL
  25 extern int errno;
  26 # endif
  27 # define __set_errno(ev) ((errno) = (ev))
  28 #endif
  29
  30 #if _LIBC || HAVE_STDLIB_H
  31 # include <stdlib.h>
  32 #endif
  33 #if _LIBC || HAVE_STRING_H
  34 # include <string.h>
  35 #endif
  36 #if _LIBC || HAVE_UNISTD_H
  37 # include <unistd.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 unsetenv __unsetenv
  62 # define clearenv __clearenv
  63 # define tfind __tfind
  64 # define tsearch __tsearch
  65 #endif
  66
  67 /* In the GNU C library implementation we try to be more clever and
  68    allow arbitrarily many changes of the environment given that the used
  69    values are from a small set.  Outside glibc this will eat up all
  70    memory after a while.  */
  71 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  72                       && defined __GNUC__)
  73 # define USE_TSEARCH    1
  74 # include <search.h>
  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 (name, value, combined, replace)
 110      const char *name;
 111      const char *value;
 112      const char *combined;
 113      int replace;
 114 {
 115   char **ep;
 116   size_t size;
 117   const size_t namelen = strlen (name);
 118   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 119
 120   LOCK;
 121
 122   /* We have to get the pointer now that we have the lock and not earlier
 123      since another thread might have created a new environment.  */
 124   ep = __environ;
 125
 126   size = 0;
 127   if (ep != NULL)
 128     {
 129       for (; *ep != NULL; ++ep)
 130         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 131           break;
 132         else
 133           ++size;
 134     }
 135
 136   if (ep == NULL || __builtin_expect (*ep == NULL, 1))
 137     {
 138       const size_t varlen = namelen + 1 + vallen;
 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           char *new_value;
 160           int use_alloca = __libc_use_alloca (varlen);
 161           if (__builtin_expect (use_alloca, 1))
 162             new_value = (char *) alloca (varlen);
 163           else
 164             {
 165               new_value = malloc (varlen);
 166               if (new_value == NULL)
 167                 {
 168                   UNLOCK;
 169                   if (last_environ == NULL)
 170                     free (new_environ);
 171                   return -1;
 172                 }
 173             }
 174 # ifdef _LIBC
 175           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 176                      value, vallen);
 177 # else
 178           memcpy (new_value, name, namelen);
 179           new_value[namelen] = '=';
 180           memcpy (&new_value[namelen + 1], value, vallen);
 181 # endif
 182
 183           new_environ[size] = KNOWN_VALUE (new_value);
 184           if (__builtin_expect (new_environ[size] == NULL, 1))
 185 #endif
 186             {
 187 #ifdef USE_TSEARCH
 188               if (__builtin_expect (! use_alloca, 0))
 189                 new_environ[size] = new_value;
 190               else
 191 #endif
 192                 {
 193                   new_environ[size] = (char *) malloc (varlen);
 194                   if (__builtin_expect (new_environ[size] == NULL, 0))
 195                     {
 196                       UNLOCK;
 197                       return -1;
 198                     }
 199
 200 #ifdef USE_TSEARCH
 201                   memcpy (new_environ[size], new_value, varlen);
 202 #else
 203                   memcpy (new_environ[size], name, namelen);
 204                   new_environ[size][namelen] = '=';
 205                   memcpy (&new_environ[size][namelen + 1], value, vallen);
 206 #endif
 207                 }
 208
 209               /* And save the value now.  We cannot do this when we remove
 210                  the string since then we cannot decide whether it is a
 211                  user string or not.  */
 212               STORE_VALUE (new_environ[size]);
 213             }
 214         }
 215
 216       if (__environ != last_environ)
 217         memcpy ((char *) new_environ, (char *) __environ,
 218                 size * sizeof (char *));
 219
 220       new_environ[size + 1] = NULL;
 221
 222       last_environ = __environ = new_environ;
 223     }
 224   else if (replace)
 225     {
 226       char *np;
 227
 228       /* Use the user string if given.  */
 229       if (combined != NULL)
 230         np = (char *) combined;
 231       else
 232         {
 233           const size_t varlen = namelen + 1 + vallen;
 234 #ifdef USE_TSEARCH
 235           char *new_value;
 236           int use_alloca = __libc_use_alloca (varlen);
 237           if (__builtin_expect (use_alloca, 1))
 238             new_value = (char *) alloca (varlen);
 239           else
 240             {
 241               new_value = malloc (varlen);
 242               if (new_value == NULL)
 243                 {
 244                   UNLOCK;
 245                   return -1;
 246                 }
 247             }
 248 # ifdef _LIBC
 249           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 250                      value, vallen);
 251 # else
 252           memcpy (new_value, name, namelen);
 253           new_value[namelen] = '=';
 254           memcpy (&new_value[namelen + 1], value, vallen);
 255 # endif
 256
 257           np = KNOWN_VALUE (new_value);
 258           if (__builtin_expect (np == NULL, 1))
 259 #endif
 260             {
 261 #ifdef USE_TSEARCH
 262               if (__builtin_expect (! use_alloca, 0))
 263                 np = new_value;
 264               else
 265 #endif
 266                 {
 267                   np = malloc (varlen);
 268                   if (__builtin_expect (np == NULL, 0))
 269                     {
 270                       UNLOCK;
 271                       return -1;
 272                     }
 273
 274 #ifdef USE_TSEARCH
 275                   memcpy (np, new_value, varlen);
 276 #else
 277                   memcpy (np, name, namelen);
 278                   np[namelen] = '=';
 279                   memcpy (&np[namelen + 1], value, vallen);
 280 #endif
 281                 }
 282               /* And remember the value.  */
 283               STORE_VALUE (np);
 284             }
 285         }
 286
 287       *ep = np;
 288     }
 289
 290   UNLOCK;
 291
 292   return 0;
 293 }
 294
 295 int
 296 setenv (name, value, replace)
 297      const char *name;
 298      const char *value;
 299      int replace;
 300 {
 301   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 302     {
 303       __set_errno (EINVAL);
 304       return -1;
 305     }
 306
 307   return __add_to_environ (name, value, NULL, replace);
 308 }
 309
 310 int
 311 unsetenv (name)
 312      const char *name;
 313 {
 314   size_t len;
 315   char **ep;
 316
 317   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 318     {
 319       __set_errno (EINVAL);
 320       return -1;
 321     }
 322
 323   len = strlen (name);
 324
 325   LOCK;
 326
 327   ep = __environ;
 328   if (ep != NULL)
 329     while (*ep != NULL)
 330       if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 331         {
 332           /* Found it.  Remove this pointer by moving later ones back.  */
 333           char **dp = ep;
 334
 335           do
 336             dp[0] = dp[1];
 337           while (*dp++);
 338           /* Continue the loop in case NAME appears again.  */
 339         }
 340       else
 341         ++ep;
 342
 343   UNLOCK;
 344
 345   return 0;
 346 }
 347
 348 /* The `clearenv' was planned to be added to POSIX.1 but probably
 349    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 350    for Fortran 77) requires this function.  */
 351 int
 352 clearenv (void)
 353 {
 354   LOCK;
 355
 356   if (__environ == last_environ && __environ != NULL)
 357     {
 358       /* We allocated this environment so we can free it.  */
 359       free (__environ);
 360       last_environ = NULL;
 361     }
 362
 363   /* Clear the environment pointer removes the whole environment.  */
 364   __environ = NULL;
 365
 366   UNLOCK;
 367
 368   return 0;
 369 }
 370 #ifdef _LIBC
 371 libc_freeres_fn (free_mem)
 372 {
 373   /* Remove all traces.  */
 374   clearenv ();
 375
 376   /* Now remove the search tree.  */
 377   __tdestroy (known_values, free);
 378   known_values = NULL;
 379 }
 380
 381 # undef setenv
 382 # undef unsetenv
 383 # undef clearenv
 384 weak_alias (__setenv, setenv)
 385 weak_alias (__unsetenv, unsetenv)
 386 weak_alias (__clearenv, clearenv)
 387 #endif