gdbsupport/scoped_ignore_signal.h

   1 /* Support for ignoring signals.
   2
   3    Copyright (C) 2021 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef SCOPED_IGNORE_SIGNAL_H
  21 #define SCOPED_IGNORE_SIGNAL_H
  22
  23 #include <signal.h>
  24
  25 /* RAII class used to ignore a signal in a scope.  If sigprocmask is
  26    supported, then the signal is only ignored by the calling thread.
  27    Otherwise, the signal disposition is set to SIG_IGN, which affects
  28    the whole process.  */
  29
  30 template <int Sig>
  31 class scoped_ignore_signal
  32 {
  33 public:
  34   scoped_ignore_signal ()
  35   {
  36 #ifdef HAVE_SIGPROCMASK
  37     sigset_t set, old_state;
  38
  39     sigemptyset (&set);
  40     sigaddset (&set, Sig);
  41     sigprocmask (SIG_BLOCK, &set, &old_state);
  42     m_was_blocked = sigismember (&old_state, Sig);
  43 #else
  44     m_osig = signal (Sig, SIG_IGN);
  45 #endif
  46   }
  47
  48   ~scoped_ignore_signal ()
  49   {
  50 #ifdef HAVE_SIGPROCMASK
  51     if (!m_was_blocked)
  52       {
  53         sigset_t set;
  54         const timespec zero_timeout = {};
  55
  56         sigemptyset (&set);
  57         sigaddset (&set, Sig);
  58
  59         /* If we got a pending Sig signal, consume it before
  60            unblocking.  */
  61         sigtimedwait (&set, nullptr, &zero_timeout);
  62
  63         sigprocmask (SIG_UNBLOCK, &set, nullptr);
  64       }
  65 #else
  66     signal (Sig, m_osig);
  67 #endif
  68   }
  69
  70   DISABLE_COPY_AND_ASSIGN (scoped_ignore_signal);
  71
  72 private:
  73 #ifdef HAVE_SIGPROCMASK
  74   bool m_was_blocked;
  75 #else
  76   sighandler_t m_osig;
  77 #endif
  78 };
  79
  80 struct scoped_ignore_signal_nop
  81 {
  82   /* Note, these can't both be "= default", because otherwise the
  83      compiler warns that variables of this type are not used.  */
  84   scoped_ignore_signal_nop ()
  85   {}
  86   ~scoped_ignore_signal_nop ()
  87   {}
  88   DISABLE_COPY_AND_ASSIGN (scoped_ignore_signal_nop);
  89 };
  90
  91 #ifdef SIGPIPE
  92 using scoped_ignore_sigpipe = scoped_ignore_signal<SIGPIPE>;
  93 #else
  94 using scoped_ignore_sigpipe = scoped_ignore_signal_nop;
  95 #endif
  96
  97 #endif /* SCOPED_IGNORE_SIGNAL_H */