gl/setenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2003,2005,2006 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
  35 # include "allocsa.h"
  36 #endif
  37
  38 #if !_LIBC
  39 # define __environ      environ
  40 # ifndef HAVE_ENVIRON_DECL
  41 extern char **environ;
  42 # endif
  43 #endif
  44
  45 #if _LIBC
  46 /* This lock protects against simultaneous modifications of `environ'.  */
  47 # include <bits/libc-lock.h>
  48 __libc_lock_define_initialized (static, envlock)
  49 # define LOCK   __libc_lock_lock (envlock)
  50 # define UNLOCK __libc_lock_unlock (envlock)
  51 #else
  52 # define LOCK
  53 # define UNLOCK
  54 #endif
  55
  56 /* In the GNU C library we must keep the namespace clean.  */
  57 #ifdef _LIBC
  58 # define setenv __setenv
  59 # define clearenv __clearenv
  60 # define tfind __tfind
  61 # define tsearch __tsearch
  62 #endif
  63
  64 /* In the GNU C library implementation we try to be more clever and
  65    allow arbitrarily many changes of the environment given that the used
  66    values are from a small set.  Outside glibc this will eat up all
  67    memory after a while.  */
  68 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  69                       && defined __GNUC__)
  70 # define USE_TSEARCH    1
  71 # include <search.h>
  72 typedef int (*compar_fn_t) (const void *, const void *);
  73
  74 /* This is a pointer to the root of the search tree with the known
  75    values.  */
  76 static void *known_values;
  77
  78 # define KNOWN_VALUE(Str) \
  79   ({                                                                          \
  80     void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);           \
  81     value != NULL ? *(char **) value : NULL;                                  \
  82   })
  83 # define STORE_VALUE(Str) \
  84   tsearch (Str, &known_values, (compar_fn_t) strcmp)
  85
  86 #else
  87 # undef USE_TSEARCH
  88
  89 # define KNOWN_VALUE(Str) NULL
  90 # define STORE_VALUE(Str) do { } while (0)
  91
  92 #endif
  93
  94
  95 /* If this variable is not a null pointer we allocated the current
  96    environment.  */
  97 static char **last_environ;
  98
  99
 100 /* This function is used by `setenv' and `putenv'.  The difference between
 101    the two functions is that for the former must create a new string which
 102    is then placed in the environment, while the argument of `putenv'
 103    must be used directly.  This is all complicated by the fact that we try
 104    to reuse values once generated for a `setenv' call since we can never
 105    free the strings.  */
 106 int
 107 __add_to_environ (const char *name, const char *value, const char *combined,
 108                   int replace)
 109 {
 110   register char **ep;
 111   register size_t size;
 112   const size_t namelen = strlen (name);
 113   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 114
 115   LOCK;
 116
 117   /* We have to get the pointer now that we have the lock and not earlier
 118      since another thread might have created a new environment.  */
 119   ep = __environ;
 120
 121   size = 0;
 122   if (ep != NULL)
 123     {
 124       for (; *ep != NULL; ++ep)
 125         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 126           break;
 127         else
 128           ++size;
 129     }
 130
 131   if (ep == NULL || *ep == NULL)
 132     {
 133       char **new_environ;
 134 #ifdef USE_TSEARCH
 135       char *new_value;
 136 #endif
 137
 138       /* We allocated this space; we can extend it.  */
 139       new_environ =
 140         (char **) (last_environ == NULL
 141                    ? malloc ((size + 2) * sizeof (char *))
 142                    : realloc (last_environ, (size + 2) * sizeof (char *)));
 143       if (new_environ == NULL)
 144         {
 145           UNLOCK;
 146           return -1;
 147         }
 148
 149       /* If the whole entry is given add it.  */
 150       if (combined != NULL)
 151         /* We must not add the string to the search tree since it belongs
 152            to the user.  */
 153         new_environ[size] = (char *) combined;
 154       else
 155         {
 156           /* See whether the value is already known.  */
 157 #ifdef USE_TSEARCH
 158 # ifdef _LIBC
 159           new_value = (char *) alloca (namelen + 1 + vallen);
 160           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 161                      value, vallen);
 162 # else
 163           new_value = (char *) allocsa (namelen + 1 + vallen);
 164           if (new_value == NULL)
 165             {
 166               __set_errno (ENOMEM);
 167               UNLOCK;
 168               return -1;
 169             }
 170           memcpy (new_value, name, namelen);
 171           new_value[namelen] = '=';
 172           memcpy (&new_value[namelen + 1], value, vallen);
 173 # endif
 174
 175           new_environ[size] = KNOWN_VALUE (new_value);
 176           if (new_environ[size] == NULL)
 177 #endif
 178             {
 179               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 180               if (new_environ[size] == NULL)
 181                 {
 182 #if defined USE_TSEARCH && !defined _LIBC
 183                   freesa (new_value);
 184 #endif
 185                   __set_errno (ENOMEM);
 186                   UNLOCK;
 187                   return -1;
 188                 }
 189
 190 #ifdef USE_TSEARCH
 191               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 192 #else
 193               memcpy (new_environ[size], name, namelen);
 194               new_environ[size][namelen] = '=';
 195               memcpy (&new_environ[size][namelen + 1], value, vallen);
 196 #endif
 197               /* And save the value now.  We cannot do this when we remove
 198                  the string since then we cannot decide whether it is a
 199                  user string or not.  */
 200               STORE_VALUE (new_environ[size]);
 201             }
 202 #if defined USE_TSEARCH && !defined _LIBC
 203           freesa (new_value);
 204 #endif
 205         }
 206
 207       if (__environ != last_environ)
 208         memcpy ((char *) new_environ, (char *) __environ,
 209                 size * sizeof (char *));
 210
 211       new_environ[size + 1] = NULL;
 212
 213       last_environ = __environ = new_environ;
 214     }
 215   else if (replace)
 216     {
 217       char *np;
 218
 219       /* Use the user string if given.  */
 220       if (combined != NULL)
 221         np = (char *) combined;
 222       else
 223         {
 224 #ifdef USE_TSEARCH
 225           char *new_value;
 226 # ifdef _LIBC
 227           new_value = alloca (namelen + 1 + vallen);
 228           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 229                      value, vallen);
 230 # else
 231           new_value = allocsa (namelen + 1 + vallen);
 232           if (new_value == NULL)
 233             {
 234               __set_errno (ENOMEM);
 235               UNLOCK;
 236               return -1;
 237             }
 238           memcpy (new_value, name, namelen);
 239           new_value[namelen] = '=';
 240           memcpy (&new_value[namelen + 1], value, vallen);
 241 # endif
 242
 243           np = KNOWN_VALUE (new_value);
 244           if (np == NULL)
 245 #endif
 246             {
 247               np = malloc (namelen + 1 + vallen);
 248               if (np == NULL)
 249                 {
 250 #if defined USE_TSEARCH && !defined _LIBC
 251                   freesa (new_value);
 252 #endif
 253                   __set_errno (ENOMEM);
 254                   UNLOCK;
 255                   return -1;
 256                 }
 257
 258 #ifdef USE_TSEARCH
 259               memcpy (np, new_value, namelen + 1 + vallen);
 260 #else
 261               memcpy (np, name, namelen);
 262               np[namelen] = '=';
 263               memcpy (&np[namelen + 1], value, vallen);
 264 #endif
 265               /* And remember the value.  */
 266               STORE_VALUE (np);
 267             }
 268 #if defined USE_TSEARCH && !defined _LIBC
 269           freesa (new_value);
 270 #endif
 271         }
 272
 273       *ep = np;
 274     }
 275
 276   UNLOCK;
 277
 278   return 0;
 279 }
 280
 281 int
 282 setenv (const char *name, const char *value, int replace)
 283 {
 284   return __add_to_environ (name, value, NULL, replace);
 285 }
 286
 287 /* The `clearenv' was planned to be added to POSIX.1 but probably
 288    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 289    for Fortran 77) requires this function.  */
 290 int
 291 clearenv (void)
 292 {
 293   LOCK;
 294
 295   if (__environ == last_environ && __environ != NULL)
 296     {
 297       /* We allocated this environment so we can free it.  */
 298       free (__environ);
 299       last_environ = NULL;
 300     }
 301
 302   /* Clear the environment pointer removes the whole environment.  */
 303   __environ = NULL;
 304
 305   UNLOCK;
 306
 307   return 0;
 308 }
 309
 310 #ifdef _LIBC
 311 static void
 312 free_mem (void)
 313 {
 314   /* Remove all traces.  */
 315   clearenv ();
 316
 317   /* Now remove the search tree.  */
 318   __tdestroy (known_values, free);
 319   known_values = NULL;
 320 }
 321 text_set_element (__libc_subfreeres, free_mem);
 322
 323
 324 # undef setenv
 325 # undef clearenv
 326 weak_alias (__setenv, setenv)
 327 weak_alias (__clearenv, clearenv)
 328 #endif