gl/setenv.c

   1 /* Copyright (C) 1992, 1995-2003, 2005-2010 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 3 of the License, or
   7    (at your option) 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
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 #if !_LIBC
  18 # include <config.h>
  19 #endif
  20
  21 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  22    optimizes away the name == NULL test below.  */
  23 #define _GL_ARG_NONNULL(params)
  24
  25 #include <alloca.h>
  26
  27 /* Specification.  */
  28 #include <stdlib.h>
  29
  30 #include <errno.h>
  31 #ifndef __set_errno
  32 # define __set_errno(ev) ((errno) = (ev))
  33 #endif
  34
  35 #include <string.h>
  36 #if _LIBC || HAVE_UNISTD_H
  37 # include <unistd.h>
  38 #endif
  39
  40 #if !_LIBC
  41 # include "malloca.h"
  42 #endif
  43
  44 #if _LIBC || !HAVE_SETENV
  45
  46 #if !_LIBC
  47 # define __environ      environ
  48 #endif
  49
  50 #if _LIBC
  51 /* This lock protects against simultaneous modifications of `environ'.  */
  52 # include <bits/libc-lock.h>
  53 __libc_lock_define_initialized (static, envlock)
  54 # define LOCK   __libc_lock_lock (envlock)
  55 # define UNLOCK __libc_lock_unlock (envlock)
  56 #else
  57 # define LOCK
  58 # define UNLOCK
  59 #endif
  60
  61 /* In the GNU C library we must keep the namespace clean.  */
  62 #ifdef _LIBC
  63 # define setenv __setenv
  64 # define clearenv __clearenv
  65 # define tfind __tfind
  66 # define tsearch __tsearch
  67 #else
  68 /* Use the system functions, not the gnulib overrides in this file.  */
  69 # undef malloc
  70 # undef realloc
  71 #endif
  72
  73 /* In the GNU C library implementation we try to be more clever and
  74    allow arbitrarily many changes of the environment given that the used
  75    values are from a small set.  Outside glibc this will eat up all
  76    memory after a while.  */
  77 #if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
  78                       && defined __GNUC__)
  79 # define USE_TSEARCH    1
  80 # include <search.h>
  81 typedef int (*compar_fn_t) (const void *, const void *);
  82
  83 /* This is a pointer to the root of the search tree with the known
  84    values.  */
  85 static void *known_values;
  86
  87 # define KNOWN_VALUE(Str) \
  88   ({                                                                          \
  89     void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);           \
  90     value != NULL ? *(char **) value : NULL;                                  \
  91   })
  92 # define STORE_VALUE(Str) \
  93   tsearch (Str, &known_values, (compar_fn_t) strcmp)
  94
  95 #else
  96 # undef USE_TSEARCH
  97
  98 # define KNOWN_VALUE(Str) NULL
  99 # define STORE_VALUE(Str) do { } while (0)
 100
 101 #endif
 102
 103
 104 /* If this variable is not a null pointer we allocated the current
 105    environment.  */
 106 static char **last_environ;
 107
 108
 109 /* This function is used by `setenv' and `putenv'.  The difference between
 110    the two functions is that for the former must create a new string which
 111    is then placed in the environment, while the argument of `putenv'
 112    must be used directly.  This is all complicated by the fact that we try
 113    to reuse values once generated for a `setenv' call since we can never
 114    free the strings.  */
 115 int
 116 __add_to_environ (const char *name, const char *value, const char *combined,
 117                   int replace)
 118 {
 119   char **ep;
 120   size_t size;
 121   const size_t namelen = strlen (name);
 122   const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
 123
 124   LOCK;
 125
 126   /* We have to get the pointer now that we have the lock and not earlier
 127      since another thread might have created a new environment.  */
 128   ep = __environ;
 129
 130   size = 0;
 131   if (ep != NULL)
 132     {
 133       for (; *ep != NULL; ++ep)
 134         if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
 135           break;
 136         else
 137           ++size;
 138     }
 139
 140   if (ep == NULL || *ep == NULL)
 141     {
 142       char **new_environ;
 143 #ifdef USE_TSEARCH
 144       char *new_value;
 145 #endif
 146
 147       /* We allocated this space; we can extend it.  */
 148       new_environ =
 149         (char **) (last_environ == NULL
 150                    ? malloc ((size + 2) * sizeof (char *))
 151                    : realloc (last_environ, (size + 2) * sizeof (char *)));
 152       if (new_environ == NULL)
 153         {
 154           /* It's easier to set errno to ENOMEM than to rely on the
 155              'malloc-posix' and 'realloc-posix' gnulib modules.  */
 156           __set_errno (ENOMEM);
 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 # ifdef _LIBC
 171           new_value = (char *) alloca (namelen + 1 + vallen);
 172           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 173                      value, vallen);
 174 # else
 175           new_value = (char *) malloca (namelen + 1 + vallen);
 176           if (new_value == NULL)
 177             {
 178               __set_errno (ENOMEM);
 179               UNLOCK;
 180               return -1;
 181             }
 182           memcpy (new_value, name, namelen);
 183           new_value[namelen] = '=';
 184           memcpy (&new_value[namelen + 1], value, vallen);
 185 # endif
 186
 187           new_environ[size] = KNOWN_VALUE (new_value);
 188           if (new_environ[size] == NULL)
 189 #endif
 190             {
 191               new_environ[size] = (char *) malloc (namelen + 1 + vallen);
 192               if (new_environ[size] == NULL)
 193                 {
 194 #if defined USE_TSEARCH && !defined _LIBC
 195                   freea (new_value);
 196 #endif
 197                   __set_errno (ENOMEM);
 198                   UNLOCK;
 199                   return -1;
 200                 }
 201
 202 #ifdef USE_TSEARCH
 203               memcpy (new_environ[size], new_value, namelen + 1 + vallen);
 204 #else
 205               memcpy (new_environ[size], name, namelen);
 206               new_environ[size][namelen] = '=';
 207               memcpy (&new_environ[size][namelen + 1], value, vallen);
 208 #endif
 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 #if defined USE_TSEARCH && !defined _LIBC
 215           freea (new_value);
 216 #endif
 217         }
 218
 219       if (__environ != last_environ)
 220         memcpy ((char *) new_environ, (char *) __environ,
 221                 size * sizeof (char *));
 222
 223       new_environ[size + 1] = NULL;
 224
 225       last_environ = __environ = new_environ;
 226     }
 227   else if (replace)
 228     {
 229       char *np;
 230
 231       /* Use the user string if given.  */
 232       if (combined != NULL)
 233         np = (char *) combined;
 234       else
 235         {
 236 #ifdef USE_TSEARCH
 237           char *new_value;
 238 # ifdef _LIBC
 239           new_value = alloca (namelen + 1 + vallen);
 240           __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
 241                      value, vallen);
 242 # else
 243           new_value = malloca (namelen + 1 + vallen);
 244           if (new_value == NULL)
 245             {
 246               __set_errno (ENOMEM);
 247               UNLOCK;
 248               return -1;
 249             }
 250           memcpy (new_value, name, namelen);
 251           new_value[namelen] = '=';
 252           memcpy (&new_value[namelen + 1], value, vallen);
 253 # endif
 254
 255           np = KNOWN_VALUE (new_value);
 256           if (np == NULL)
 257 #endif
 258             {
 259               np = (char *) malloc (namelen + 1 + vallen);
 260               if (np == NULL)
 261                 {
 262 #if defined USE_TSEARCH && !defined _LIBC
 263                   freea (new_value);
 264 #endif
 265                   __set_errno (ENOMEM);
 266                   UNLOCK;
 267                   return -1;
 268                 }
 269
 270 #ifdef USE_TSEARCH
 271               memcpy (np, new_value, namelen + 1 + vallen);
 272 #else
 273               memcpy (np, name, namelen);
 274               np[namelen] = '=';
 275               memcpy (&np[namelen + 1], value, vallen);
 276 #endif
 277               /* And remember the value.  */
 278               STORE_VALUE (np);
 279             }
 280 #if defined USE_TSEARCH && !defined _LIBC
 281           freea (new_value);
 282 #endif
 283         }
 284
 285       *ep = np;
 286     }
 287
 288   UNLOCK;
 289
 290   return 0;
 291 }
 292
 293 int
 294 setenv (const char *name, const char *value, int replace)
 295 {
 296   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
 297     {
 298       __set_errno (EINVAL);
 299       return -1;
 300     }
 301
 302   return __add_to_environ (name, value, NULL, replace);
 303 }
 304
 305 /* The `clearenv' was planned to be added to POSIX.1 but probably
 306    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 307    for Fortran 77) requires this function.  */
 308 int
 309 clearenv (void)
 310 {
 311   LOCK;
 312
 313   if (__environ == last_environ && __environ != NULL)
 314     {
 315       /* We allocated this environment so we can free it.  */
 316       free (__environ);
 317       last_environ = NULL;
 318     }
 319
 320   /* Clear the environment pointer removes the whole environment.  */
 321   __environ = NULL;
 322
 323   UNLOCK;
 324
 325   return 0;
 326 }
 327
 328 #ifdef _LIBC
 329 static void
 330 free_mem (void)
 331 {
 332   /* Remove all traces.  */
 333   clearenv ();
 334
 335   /* Now remove the search tree.  */
 336   __tdestroy (known_values, free);
 337   known_values = NULL;
 338 }
 339 text_set_element (__libc_subfreeres, free_mem);
 340
 341
 342 # undef setenv
 343 # undef clearenv
 344 weak_alias (__setenv, setenv)
 345 weak_alias (__clearenv, clearenv)
 346 #endif
 347
 348 #endif /* _LIBC || !HAVE_SETENV */
 349
 350 /* The rest of this file is called into use when replacing an existing
 351    but buggy setenv.  Known bugs include failure to diagnose invalid
 352    name, and consuming a leading '=' from value.  */
 353 #if HAVE_SETENV
 354
 355 # undef setenv
 356 # define STREQ(a, b) (strcmp (a, b) == 0)
 357
 358 int
 359 rpl_setenv (const char *name, const char *value, int replace)
 360 {
 361   int result;
 362   if (!name || !*name || strchr (name, '='))
 363     {
 364       errno = EINVAL;
 365       return -1;
 366     }
 367   /* Call the real setenv even if replace is 0, in case implementation
 368      has underlying data to update, such as when environ changes.  */
 369   result = setenv (name, value, replace);
 370   if (result == 0 && replace && *value == '=')
 371     {
 372       char *tmp = getenv (name);
 373       if (!STREQ (tmp, value))
 374         {
 375           int saved_errno;
 376           size_t len = strlen (value);
 377           tmp = malloca (len + 2);
 378           /* Since leading '=' is eaten, double it up.  */
 379           *tmp = '=';
 380           memcpy (tmp + 1, value, len + 1);
 381           result = setenv (name, tmp, replace);
 382           saved_errno = errno;
 383           freea (tmp);
 384           errno = saved_errno;
 385         }
 386     }
 387   return result;
 388 }
 389
 390 #endif /* HAVE_SETENV */