locale/uselocale.c

   1 /* uselocale -- fetch and set the current per-thread locale
   2    Copyright (C) 2002, 2004, 2007 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <locale.h>
  21 #include "localeinfo.h"
  22 #include <ctype.h>
  23
  24 /* Switch the current thread's locale to DATASET.
  25    If DATASET is null, instead just return the current setting.
  26    The special value LC_GLOBAL_LOCALE is the initial setting
  27    for all threads, and means the thread uses the global
  28    setting controlled by `setlocale'.  */
  29 locale_t
  30 __uselocale (locale_t newloc)
  31 {
  32   locale_t oldloc = _NL_CURRENT_LOCALE;
  33
  34   if (newloc != NULL)
  35     {
  36       const locale_t locobj
  37         = newloc == LC_GLOBAL_LOCALE ? &_nl_global_locale : newloc;
  38       __libc_tsd_set (LOCALE, locobj);
  39
  40 #ifdef NL_CURRENT_INDIRECT
  41       /* Now we must update all the per-category thread-local variables to
  42          point into the new current locale for this thread.  The magic
  43          symbols _nl_current_LC_FOO_used are defined to meaningless values
  44          if _nl_current_LC_FOO was linked in.  By using weak references to
  45          both symbols and testing the address of _nl_current_LC_FOO_used,
  46          we can avoid accessing the _nl_current_LC_FOO thread-local
  47          variable at all when no code referring to it was linked in.  We
  48          need the special bogus symbol because while TLS symbols can be
  49          weak, there is no reasonable way to test for the default-zero
  50          value as with a heap symbol (taking the address would just use
  51          some bogus offset from our thread pointer).  */
  52
  53 # define DEFINE_CATEGORY(category, category_name, items, a) \
  54       {                                                                       \
  55         extern char _nl_current_##category##_used;                            \
  56         weak_extern (_nl_current_##category##_used)                           \
  57         weak_extern (_nl_current_##category)                                  \
  58         if (&_nl_current_##category##_used != 0)                              \
  59           _nl_current_##category = &locobj->__locales[category];              \
  60       }
  61 # include "categories.def"
  62 # undef DEFINE_CATEGORY
  63 #endif
  64
  65       /* Update the special tsd cache of some locale data.  */
  66       __libc_tsd_set (CTYPE_B, (void *) locobj->__ctype_b);
  67       __libc_tsd_set (CTYPE_TOLOWER, (void *) locobj->__ctype_tolower);
  68       __libc_tsd_set (CTYPE_TOUPPER, (void *) locobj->__ctype_toupper);
  69     }
  70
  71   return oldloc == &_nl_global_locale ? LC_GLOBAL_LOCALE : oldloc;
  72 }
  73 libc_hidden_def (__uselocale)
  74 weak_alias (__uselocale, uselocale)