gcc/doc/gcc/c-implementation-defined-behavior/characters.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _characters-implementation:
   7
   8 Characters
   9 **********
  10
  11 * The number of bits in a byte (C90 3.4, C99 and C11 3.6).
  12
  13   Determined by ABI.
  14
  15 * The values of the members of the execution character set (C90,
  16   C99 and C11 5.2.1).
  17
  18   Determined by ABI.
  19
  20 * The unique value of the member of the execution character set produced
  21   for each of the standard alphabetic escape sequences (C90, C99 and C11
  22   5.2.2).
  23
  24   Determined by ABI.
  25
  26 * The value of a ``char`` object into which has been stored any
  27   character other than a member of the basic execution character set
  28   (C90 6.1.2.5, C99 and C11 6.2.5).
  29
  30   Determined by ABI.
  31
  32 * Which of ``signed char`` or ``unsigned char`` has the same
  33   range, representation, and behavior as 'plain' ``char`` (C90
  34   6.1.2.5, C90 6.2.1.1, C99 and C11 6.2.5, C99 and C11 6.3.1.1).
  35
  36   .. index:: fsigned-char, funsigned-char
  37
  38   Determined by ABI.  The options :option:`-funsigned-char` and
  39   :option:`-fsigned-char` change the default.  See :ref:`c-dialect-options`.
  40
  41 * The mapping of members of the source character set (in character
  42   constants and string literals) to members of the execution character
  43   set (C90 6.1.3.4, C99 and C11 6.4.4.4, C90, C99 and C11 5.1.1.2).
  44
  45   Determined by ABI.
  46
  47 * The value of an integer character constant containing more than one
  48   character or containing a character or escape sequence that does not map
  49   to a single-byte execution character (C90 6.1.3.4, C99 and C11 6.4.4.4).
  50
  51   See :ref:`cpp:implementation-defined-behavior`.
  52
  53 * The value of a wide character constant containing more than one
  54   multibyte character or a single multibyte character that maps to
  55   multiple members of the extended execution character set, or
  56   containing a multibyte character or escape sequence not represented in
  57   the extended execution character set (C90 6.1.3.4, C99 and C11
  58   6.4.4.4).
  59
  60   See :ref:`cpp:implementation-defined-behavior`.
  61
  62 * The current locale used to convert a wide character constant consisting
  63   of a single multibyte character that maps to a member of the extended
  64   execution character set into a corresponding wide character code (C90
  65   6.1.3.4, C99 and C11 6.4.4.4).
  66
  67   See :ref:`cpp:implementation-defined-behavior`.
  68
  69 * Whether differently-prefixed wide string literal tokens can be
  70   concatenated and, if so, the treatment of the resulting multibyte
  71   character sequence (C11 6.4.5).
  72
  73   Such tokens may not be concatenated.
  74
  75 * The current locale used to convert a wide string literal into
  76   corresponding wide character codes (C90 6.1.4, C99 and C11 6.4.5).
  77
  78   See :ref:`cpp:implementation-defined-behavior`.
  79
  80 * The value of a string literal containing a multibyte character or escape
  81   sequence not represented in the execution character set (C90 6.1.4,
  82   C99 and C11 6.4.5).
  83
  84   See :ref:`cpp:implementation-defined-behavior`.
  85
  86 * The encoding of any of ``wchar_t``, ``char16_t``, and
  87   ``char32_t`` where the corresponding standard encoding macro
  88   (``__STDC_ISO_10646__``, ``__STDC_UTF_16__``, or
  89   ``__STDC_UTF_32__``) is not defined (C11 6.10.8.2).
  90
  91   See :ref:`cpp:implementation-defined-behavior`.  ``char16_t`` and
  92   ``char32_t`` literals are always encoded in UTF-16 and UTF-32
  93   respectively.