lib/stdnoreturn.in.h

   1 /* A substitute for ISO C11 <stdnoreturn.h>.
   2
   3    Copyright 2012-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 /* This file uses _Noreturn.  */
  21 #if !_GL_CONFIG_H_INCLUDED
  22  #error "Please include config.h first."
  23 #endif
  24
  25 #ifndef noreturn
  26
  27 /* ISO C11 <stdnoreturn.h> for platforms that lack it.
  28
  29    References:
  30    ISO C11 (latest free draft
  31    <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>)
  32    section 7.23
  33
  34    <stdnoreturn.h> is obsolescent in C23, so new code should avoid it.  */
  35
  36 /* The definition of _Noreturn is copied here.  */
  37
  38 #if 1200 <= _MSC_VER || defined __CYGWIN__
  39 /* On MSVC, standard include files contain declarations like
  40      __declspec (noreturn) void abort (void);
  41    "#define noreturn _Noreturn" would cause this declaration to be rewritten
  42    to the invalid
  43      __declspec (__declspec (noreturn)) void abort (void);
  44
  45    Similarly, on Cygwin, standard include files contain declarations like
  46      void __cdecl abort (void) __attribute__ ((noreturn));
  47    "#define noreturn _Noreturn" would cause this declaration to be rewritten
  48    to the invalid
  49      void __cdecl abort (void) __attribute__ ((__attribute__ ((__noreturn__))));
  50
  51    Instead, define noreturn to empty, so that such declarations are rewritten to
  52      __declspec () void abort (void);
  53    or
  54      void __cdecl abort (void) __attribute__ (());
  55    respectively.  This gives up on noreturn's advice to the compiler but at
  56    least it is valid code.  */
  57 # define noreturn /*empty*/
  58 #else
  59 # define noreturn _Noreturn
  60 #endif
  61
  62 /* Did he ever return?
  63    No he never returned
  64    And his fate is still unlearn'd ...
  65      -- Steiner J, Hawes BL.  M.T.A. (1949)  */
  66
  67 #endif /* noreturn */