locale/broken_cur_max.c

   1 /* Return number of characters in multibyte representation for current
   2    character set.
   3    Copyright (C) 1996-2023 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <langinfo.h>
  21 #include <locale.h>
  22 #include <stdlib.h>
  23 #include "localeinfo.h"
  24
  25
  26 /* This is a gross hack to get broken programs running.
  27
  28    ISO C provides no mean to find out how many bytes the wide
  29    character representation really uses.  But it defines MB_CUR_LEN to
  30    return the information for the multi-byte character representation.
  31    Many programmers don't know the difference between the two and
  32    think this means the same.  But assuming all characters have a size
  33    of MB_CUR_LEN after they have been processed by `mbrtowc' is wrong.
  34    Instead the maximum number of characters used for the conversion is
  35    MB_CUR_LEN.
  36
  37    It is known that some Motif applications have this problem.  To
  38    cure this one has to make sure the glibc uses the function in this
  39    file instead of the one in locale/mb_cur_max.c.  This can either be
  40    done by linking with this file or by using the LD_PRELOAD feature
  41    of the dynamic linker.  */
  42 size_t
  43 __ctype_get_mb_cur_max (void)
  44 {
  45   union locale_data_value u;
  46
  47   u.string = nl_langinfo (_NL_CTYPE_MB_CUR_MAX);
  48   return ((size_t []) { 1, 1, 1, 2, 2, 3, 4 })[u.word];
  49 }