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    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    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    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <alloca.h>
  24
  25 #include <errno.h>
  26 #if !_LIBC
  27 # if !defined errno && !defined HAVE_ERRNO_DECL
  28 extern int errno;
  29 # endif
  30 # define __set_errno(ev) ((errno) = (ev))
  31 #endif
  32
  33 #if _LIBC || HAVE_STDLIB_H
  34 # include <stdlib.h>
  35 #endif
  36 #if _LIBC || HAVE_STRING_H
  37 # include <string.h>
  38 #endif
  39 #if _LIBC || HAVE_UNISTD_H
  40 # include <unistd.h>
  41 #endif
  42
  43 /* For those losing systems which don't have 'alloca' we have to add
  44    some additional code emulating it.  */
  45 #if _LIBC || HAVE_ALLOCA
  46 # define freea(p) /* nothing */
  47 #else
  48 # define alloca(n) malloc (n)
  49 # define freea(p) free (p)
  50 #endif
  51
  52 #if !_LIBC
  53 # define __environ      environ
  54 # ifndef HAVE_ENVIRON_DECL
  55 extern char **environ;
  56 # endif
  57 #endif
  58
  59 #if _LIBC
  60 /* This lock protects against simultaneous modifications of `environ'.  */
  61 # include <bits/libc-lock.h>
  62 __libc_lock_define_initialized (static, envlock)
  63 # define LOCK   __libc_lock_lock (envlock)
  64 # define UNLOCK __libc_lock_unlock (envlock)
  65 #else
  66 # define LOCK
  67 # define UNLOCK
  68 #endif
  69
  70 /* In the GNU C library we must keep the namespace clean.  */
  71 #ifdef _LIBC
  72 # define setenv __setenv
  73 # define clearenv __clearenv
  74 # define tfind __tfind
  75 # define tsearch __tsearch
  76 #endif
  77
  78 /* In the GNU C library implementation we try to be more clever and
  79    allow arbitrarily many changes of the environment given that the used
  80    values are from a small set.  Outside glibc this will eat up all
  81    memory after a while.  */
  82 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  83                       && defined __GNUC__)
  84 # define USE_TSEARCH    1
  85 # include <search.h>
  86 typedef int (*compar_fn_t) (const void *, const void *);
  87
  88 /* This is a pointer to the root of the search tree with the known
  89    values.  */
  90 static void *known_values;
  91
  92 # define KNOWN_VALUE(Str) \
  93   ({                                                                          \
  94     void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);           \
  95     value != NULL ? *(char **) value : NULL;                                  \
  96   })
  97 # define STORE_VALUE(Str) \
  98   tsearch (Str, &known_values, (compar_fn_t) strcmp)
  99
 100 #else
 101 # undef USE_TSEARCH
 102
 103 # define KNOWN_VALUE(Str) NULL
 104 # define STORE_VALUE(Str) do { } while (0)
 105
 106 #endif
 107
 108
 109 /* If this variable is not a null pointer we allocated the current
 110    environment.  */
 111 static char **last_environ;
 112
 113
 114 /* This function is used by `setenv' and `putenv'.  The difference between
 115    the two functions is that for the former must create a new string which
 116    is then placed in the environment, while the argument of `putenv'
 117    must be used directly.  This is all complicated by the fact that we try
 118    to reuse values once generated for a `setenv' call since we can never
 119    free the strings.  */
 120 int
 121 __add_to_environ (const char *name, const char *value, const char *combined,
 122                   int replace)
 123 {
 124   register char **ep;
 125   register size_t size;
 126   const size_t namelen = strlen (name);
 127   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 128
 129   LOCK;
 130
 131   /* We have to get the pointer now that we have the lock and not earlier
 132      since another thread might have created a new environment.  */
 133   ep = __environ;
 134
 135   size = 0;
 136   if (ep != NULL)
 137     {
 138       for (; *ep != NULL; ++ep)
 139         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 140           break;
 141         else
 142           ++size;
 143     }
 144
 145   if (ep == NULL || *ep == NULL)
 146     {
 147       char **new_environ;
 148 #ifdef USE_TSEARCH
 149       char *new_value;
 150 #endif
 151
 152       /* We allocated this space; we can extend it.  */
 153       new_environ =
 154         (char **) (last_environ == NULL
 155                    ? malloc ((size + 2) * sizeof (char *))
 156                    : realloc (last_environ, (size + 2) * sizeof (char *)));
 157       if (new_environ == NULL)
 158         {
 159           UNLOCK;
 160           return -1;
 161         }
 162
 163       /* If the whole entry is given add it.  */
 164       if (combined != NULL)
 165         /* We must not add the string to the search tree since it belongs
 166            to the user.  */
 167         new_environ[size] = (char *) combined;
 168       else
 169         {
 170           /* See whether the value is already known.  */
 171 #ifdef USE_TSEARCH
 172           new_value = (char *) alloca (namelen + 1 + vallen);
 173 # ifdef _LIBC
 174           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 175                      value, vallen);
 176 # else
 177           memcpy (new_value, name, namelen);
 178           new_value[namelen] = '=';
 179           memcpy (&new_value[namelen + 1], value, vallen);
 180 # endif
 181
 182           new_environ[size] = KNOWN_VALUE (new_value);
 183           if (new_environ[size] == NULL)
 184 #endif
 185             {
 186               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 187               if (new_environ[size] == NULL)
 188                 {
 189 #ifdef USE_TSEARCH
 190                   freea (new_value);
 191 #endif
 192                   __set_errno (ENOMEM);
 193                   UNLOCK;
 194                   return -1;
 195                 }
 196
 197 #ifdef USE_TSEARCH
 198               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 199 #else
 200               memcpy (new_environ[size], name, namelen);
 201               new_environ[size][namelen] = '=';
 202               memcpy (&new_environ[size][namelen + 1], value, vallen);
 203 #endif
 204               /* And save the value now.  We cannot do this when we remove
 205                  the string since then we cannot decide whether it is a
 206                  user string or not.  */
 207               STORE_VALUE (new_environ[size]);
 208             }
 209 #ifdef USE_TSEARCH
 210           freea (new_value);
 211 #endif
 212         }
 213
 214       if (__environ != last_environ)
 215         memcpy ((char *) new_environ, (char *) __environ,
 216                 size * sizeof (char *));
 217
 218       new_environ[size + 1] = NULL;
 219
 220       last_environ = __environ = new_environ;
 221     }
 222   else if (replace)
 223     {
 224       char *np;
 225
 226       /* Use the user string if given.  */
 227       if (combined != NULL)
 228         np = (char *) combined;
 229       else
 230         {
 231 #ifdef USE_TSEARCH
 232           char *new_value = alloca (namelen + 1 + vallen);
 233 # ifdef _LIBC
 234           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 235                      value, vallen);
 236 # else
 237           memcpy (new_value, name, namelen);
 238           new_value[namelen] = '=';
 239           memcpy (&new_value[namelen + 1], value, vallen);
 240 # endif
 241
 242           np = KNOWN_VALUE (new_value);
 243           if (np == NULL)
 244 #endif
 245             {
 246               np = malloc (namelen + 1 + vallen);
 247               if (np == NULL)
 248                 {
 249 #ifdef USE_TSEARCH
 250                   freea (new_value);
 251 #endif
 252                   UNLOCK;
 253                   return -1;
 254                 }
 255
 256 #ifdef USE_TSEARCH
 257               memcpy (np, new_value, namelen + 1 + vallen);
 258 #else
 259               memcpy (np, name, namelen);
 260               np[namelen] = '=';
 261               memcpy (&np[namelen + 1], value, vallen);
 262 #endif
 263               /* And remember the value.  */
 264               STORE_VALUE (np);
 265             }
 266 #ifdef USE_TSEARCH
 267           freea (new_value);
 268 #endif
 269         }
 270
 271       *ep = np;
 272     }
 273
 274   UNLOCK;
 275
 276   return 0;
 277 }
 278
 279 int
 280 setenv (const char *name, const char *value, int replace)
 281 {
 282   return __add_to_environ (name, value, NULL, replace);
 283 }
 284
 285 /* The `clearenv' was planned to be added to POSIX.1 but probably
 286    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 287    for Fortran 77) requires this function.  */
 288 int
 289 clearenv ()
 290 {
 291   LOCK;
 292
 293   if (__environ == last_environ && __environ != NULL)
 294     {
 295       /* We allocated this environment so we can free it.  */
 296       free (__environ);
 297       last_environ = NULL;
 298     }
 299
 300   /* Clear the environment pointer removes the whole environment.  */
 301   __environ = NULL;
 302
 303   UNLOCK;
 304
 305   return 0;
 306 }
 307
 308 #ifdef _LIBC
 309 static void
 310 free_mem (void)
 311 {
 312   /* Remove all traces.  */
 313   clearenv ();
 314
 315   /* Now remove the search tree.  */
 316   __tdestroy (known_values, free);
 317   known_values = NULL;
 318 }
 319 text_set_element (__libc_subfreeres, free_mem);
 320
 321
 322 # undef setenv
 323 # undef clearenv
 324 weak_alias (__setenv, setenv)
 325 weak_alias (__clearenv, clearenv)
 326 #endif