lib/sig-handler.h

   1 /* Convenience declarations when working with <signal.h>.
   2
   3    Copyright (C) 2008-2024 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 #ifndef _GL_SIG_HANDLER_H
  19 #define _GL_SIG_HANDLER_H
  20
  21 /* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE, _GL_ATTRIBUTE_PURE.  */
  22 #if !_GL_CONFIG_H_INCLUDED
  23  #error "Please include config.h first."
  24 #endif
  25
  26 #include <signal.h>
  27
  28 _GL_INLINE_HEADER_BEGIN
  29 #ifndef SIG_HANDLER_INLINE
  30 # define SIG_HANDLER_INLINE _GL_INLINE
  31 #endif
  32
  33 /* Convenience type when working with signal handlers.  */
  34 typedef void (*sa_handler_t) (int);
  35
  36 /* Return the handler of a signal, as a sa_handler_t value regardless
  37    of its true type.  The resulting function can be compared to
  38    special values like SIG_IGN but it is not portable to call it.  */
  39 SIG_HANDLER_INLINE sa_handler_t _GL_ATTRIBUTE_PURE
  40 get_handler (struct sigaction const *a)
  41 {
  42   /* POSIX says that special values like SIG_IGN can only occur when
  43      action.sa_flags does not contain SA_SIGINFO.  But in Linux 2.4,
  44      for example, sa_sigaction and sa_handler are aliases and a signal
  45      is ignored if sa_sigaction (after casting) equals SIG_IGN.  In
  46      this case, this implementation relies on the fact that the two
  47      are aliases, and simply returns sa_handler.  */
  48   return a->sa_handler;
  49 }
  50
  51 _GL_INLINE_HEADER_END
  52
  53 #endif /* _GL_SIG_HANDLER_H */