locale/uselocale.c

   1 /* uselocale -- fetch and set the current per-thread locale
   2    Copyright (C) 2002-2021 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <locale.h>
  20 #include "localeinfo.h"
  21 #include <ctype.h>
  22
  23 /* Switch the current thread's locale to DATASET.
  24    If DATASET is null, instead just return the current setting.
  25    The special value LC_GLOBAL_LOCALE is the initial setting
  26    for all threads, and means the thread uses the global
  27    setting controlled by `setlocale'.  */
  28 locale_t
  29 __uselocale (locale_t newloc)
  30 {
  31   locale_t oldloc = _NL_CURRENT_LOCALE;
  32
  33   if (newloc != NULL)
  34     {
  35       const locale_t locobj
  36         = newloc == LC_GLOBAL_LOCALE ? &_nl_global_locale : newloc;
  37       __libc_tsd_set (locale_t, LOCALE, locobj);
  38
  39 #ifdef NL_CURRENT_INDIRECT
  40       /* Now we must update all the per-category thread-local variables to
  41          point into the new current locale for this thread.  The magic
  42          symbols _nl_current_LC_FOO_used are defined to meaningless values
  43          if _nl_current_LC_FOO was linked in.  By using weak references to
  44          both symbols and testing the address of _nl_current_LC_FOO_used,
  45          we can avoid accessing the _nl_current_LC_FOO thread-local
  46          variable at all when no code referring to it was linked in.  We
  47          need the special bogus symbol because while TLS symbols can be
  48          weak, there is no reasonable way to test for the default-zero
  49          value as with a heap symbol (taking the address would just use
  50          some bogus offset from our thread pointer).  */
  51
  52 # define DEFINE_CATEGORY(category, category_name, items, a) \
  53       {                                                                       \
  54         extern char _nl_current_##category##_used;                            \
  55         weak_extern (_nl_current_##category##_used)                           \
  56         weak_extern (_nl_current_##category)                                  \
  57         if (&_nl_current_##category##_used != 0)                              \
  58           _nl_current_##category = &locobj->__locales[category];              \
  59       }
  60 # include "categories.def"
  61 # undef DEFINE_CATEGORY
  62 #endif
  63
  64       /* Update the special tsd cache of some locale data.  */
  65       __libc_tsd_set (const uint16_t *, CTYPE_B, (void *) locobj->__ctype_b);
  66       __libc_tsd_set (const int32_t *, CTYPE_TOLOWER,
  67                       (void *) locobj->__ctype_tolower);
  68       __libc_tsd_set (const int32_t *, CTYPE_TOUPPER,
  69                       (void *) locobj->__ctype_toupper);
  70     }
  71
  72   return oldloc == &_nl_global_locale ? LC_GLOBAL_LOCALE : oldloc;
  73 }
  74 libc_hidden_def (__uselocale)
  75 weak_alias (__uselocale, uselocale)