stdlib/setenv.c

   1 /* Copyright (C) 1992,1995-2001,2004, 2008, 2010 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       const size_t varlen = namelen + 1 + vallen;
 140       char **new_environ;
 141
 142       /* We allocated this space; we can extend it.  */
 143       new_environ = (char **) realloc (last_environ,
 144                                        (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           char *new_value;
 161           int use_alloca = __libc_use_alloca (varlen);
 162           if (__builtin_expect (use_alloca, 1))
 163             new_value = (char *) alloca (varlen);
 164           else
 165             {
 166               new_value = malloc (varlen);
 167               if (new_value == NULL)
 168                 {
 169                   UNLOCK;
 170                   if (last_environ == NULL)
 171                     free (new_environ);
 172                   return -1;
 173                 }
 174             }
 175 # ifdef _LIBC
 176           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 177                      value, vallen);
 178 # else
 179           memcpy (new_value, name, namelen);
 180           new_value[namelen] = '=';
 181           memcpy (&new_value[namelen + 1], value, vallen);
 182 # endif
 183
 184           new_environ[size] = KNOWN_VALUE (new_value);
 185           if (__builtin_expect (new_environ[size] == NULL, 1))
 186 #endif
 187             {
 188 #ifdef USE_TSEARCH
 189               if (__builtin_expect (! use_alloca, 0))
 190                 new_environ[size] = new_value;
 191               else
 192 #endif
 193                 {
 194                   new_environ[size] = (char *) malloc (varlen);
 195                   if (__builtin_expect (new_environ[size] == NULL, 0))
 196                     {
 197                       UNLOCK;
 198                       return -1;
 199                     }
 200
 201 #ifdef USE_TSEARCH
 202                   memcpy (new_environ[size], new_value, varlen);
 203 #else
 204                   memcpy (new_environ[size], name, namelen);
 205                   new_environ[size][namelen] = '=';
 206                   memcpy (&new_environ[size][namelen + 1], value, vallen);
 207 #endif
 208                 }
 209
 210               /* And save the value now.  We cannot do this when we remove
 211                  the string since then we cannot decide whether it is a
 212                  user string or not.  */
 213               STORE_VALUE (new_environ[size]);
 214             }
 215         }
 216
 217       if (__environ != last_environ)
 218         memcpy ((char *) new_environ, (char *) __environ,
 219                 size * sizeof (char *));
 220
 221       new_environ[size + 1] = NULL;
 222
 223       last_environ = __environ = new_environ;
 224     }
 225   else if (replace)
 226     {
 227       char *np;
 228
 229       /* Use the user string if given.  */
 230       if (combined != NULL)
 231         np = (char *) combined;
 232       else
 233         {
 234           const size_t varlen = namelen + 1 + vallen;
 235 #ifdef USE_TSEARCH
 236           char *new_value;
 237           int use_alloca = __libc_use_alloca (varlen);
 238           if (__builtin_expect (use_alloca, 1))
 239             new_value = (char *) alloca (varlen);
 240           else
 241             {
 242               new_value = malloc (varlen);
 243               if (new_value == NULL)
 244                 {
 245                   UNLOCK;
 246                   return -1;
 247                 }
 248             }
 249 # ifdef _LIBC
 250           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 251                      value, vallen);
 252 # else
 253           memcpy (new_value, name, namelen);
 254           new_value[namelen] = '=';
 255           memcpy (&new_value[namelen + 1], value, vallen);
 256 # endif
 257
 258           np = KNOWN_VALUE (new_value);
 259           if (__builtin_expect (np == NULL, 1))
 260 #endif
 261             {
 262 #ifdef USE_TSEARCH
 263               if (__builtin_expect (! use_alloca, 0))
 264                 np = new_value;
 265               else
 266 #endif
 267                 {
 268                   np = malloc (varlen);
 269                   if (__builtin_expect (np == NULL, 0))
 270                     {
 271                       UNLOCK;
 272                       return -1;
 273                     }
 274
 275 #ifdef USE_TSEARCH
 276                   memcpy (np, new_value, varlen);
 277 #else
 278                   memcpy (np, name, namelen);
 279                   np[namelen] = '=';
 280                   memcpy (&np[namelen + 1], value, vallen);
 281 #endif
 282                 }
 283               /* And remember the value.  */
 284               STORE_VALUE (np);
 285             }
 286         }
 287
 288       *ep = np;
 289     }
 290
 291   UNLOCK;
 292
 293   return 0;
 294 }
 295
 296 int
 297 setenv (name, value, replace)
 298      const char *name;
 299      const char *value;
 300      int replace;
 301 {
 302   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 303     {
 304       __set_errno (EINVAL);
 305       return -1;
 306     }
 307
 308   return __add_to_environ (name, value, NULL, replace);
 309 }
 310
 311 int
 312 unsetenv (name)
 313      const char *name;
 314 {
 315   size_t len;
 316   char **ep;
 317
 318   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 319     {
 320       __set_errno (EINVAL);
 321       return -1;
 322     }
 323
 324   len = strlen (name);
 325
 326   LOCK;
 327
 328   ep = __environ;
 329   if (ep != NULL)
 330     while (*ep != NULL)
 331       if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 332         {
 333           /* Found it.  Remove this pointer by moving later ones back.  */
 334           char **dp = ep;
 335
 336           do
 337             dp[0] = dp[1];
 338           while (*dp++);
 339           /* Continue the loop in case NAME appears again.  */
 340         }
 341       else
 342         ++ep;
 343
 344   UNLOCK;
 345
 346   return 0;
 347 }
 348
 349 /* The `clearenv' was planned to be added to POSIX.1 but probably
 350    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 351    for Fortran 77) requires this function.  */
 352 int
 353 clearenv ()
 354 {
 355   LOCK;
 356
 357   if (__environ == last_environ && __environ != NULL)
 358     {
 359       /* We allocated this environment so we can free it.  */
 360       free (__environ);
 361       last_environ = NULL;
 362     }
 363
 364   /* Clear the environment pointer removes the whole environment.  */
 365   __environ = NULL;
 366
 367   UNLOCK;
 368
 369   return 0;
 370 }
 371 #ifdef _LIBC
 372 libc_freeres_fn (free_mem)
 373 {
 374   /* Remove all traces.  */
 375   clearenv ();
 376
 377   /* Now remove the search tree.  */
 378   __tdestroy (known_values, free);
 379   known_values = NULL;
 380 }
 381
 382 # undef setenv
 383 # undef unsetenv
 384 # undef clearenv
 385 weak_alias (__setenv, setenv)
 386 weak_alias (__unsetenv, unsetenv)
 387 weak_alias (__clearenv, clearenv)
 388 #endif