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