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99624310dd
The macOS platform does not provide sigtimedwait, so we get:
CXX compile/compile.o
In file included from /Users/smarchi/src/binutils-gdb/gdb/compile/compile.c:46:
/Users/smarchi/src/binutils-gdb/gdb/../gdbsupport/scoped_ignore_signal.h:69:4: error: use of undeclared identifier 'sigtimedwait'
sigtimedwait (&set, nullptr, &zero_timeout);
^
An alternative to sigtimedwait with a timeout of 0 is to use sigpending,
to first check which signals are pending, and then sigwait, to consume
them. Since that's slightly more expensive (2 syscalls instead of 1),
keep using sigtimedwait for the platforms that provide it, and fall back
to sigpending + sigwait for the others.
gdbsupport/ChangeLog:
* scoped_ignore_signal.h (struct scoped_ignore_signal)
<~scoped_ignore_signal>: Use sigtimedwait if HAVE_SIGTIMEDWAIT
is defined, else use sigpending + sigwait.
Change-Id: I2a72798337e81dd1bbd21214736a139dd350af87
Co-Authored-By: John Baldwin <jhb@FreeBSD.org>
117 lines
3.1 KiB
C++
117 lines
3.1 KiB
C++
/* Support for ignoring signals.
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Copyright (C) 2021 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef SCOPED_IGNORE_SIGNAL_H
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#define SCOPED_IGNORE_SIGNAL_H
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#include <signal.h>
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/* RAII class used to ignore a signal in a scope. If sigprocmask is
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supported, then the signal is only ignored by the calling thread.
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Otherwise, the signal disposition is set to SIG_IGN, which affects
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the whole process. If ConsumePending is true, the destructor
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consumes a pending Sig. SIGPIPE for example is queued on the
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thread even if blocked at the time the pipe is written to. SIGTTOU
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OTOH is not raised at all if the thread writing to the terminal has
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it blocked. Because SIGTTOU is sent to the whole process instead
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of to a specific thread, consuming a pending SIGTTOU in the
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destructor could consume a signal raised due to actions done by
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some other thread. */
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template <int Sig, bool ConsumePending>
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class scoped_ignore_signal
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{
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public:
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scoped_ignore_signal ()
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{
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#ifdef HAVE_SIGPROCMASK
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sigset_t set, old_state;
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sigemptyset (&set);
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sigaddset (&set, Sig);
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sigprocmask (SIG_BLOCK, &set, &old_state);
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m_was_blocked = sigismember (&old_state, Sig);
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#else
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m_osig = signal (Sig, SIG_IGN);
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#endif
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}
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~scoped_ignore_signal ()
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{
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#ifdef HAVE_SIGPROCMASK
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if (!m_was_blocked)
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{
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sigset_t set;
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sigemptyset (&set);
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sigaddset (&set, Sig);
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/* If we got a pending Sig signal, consume it before
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unblocking. */
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if (ConsumePending)
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{
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#ifdef HAVE_SIGTIMEDWAIT
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const timespec zero_timeout = {};
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sigtimedwait (&set, nullptr, &zero_timeout);
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#else
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sigset_t pending;
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sigpending (&pending);
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if (sigismember (&pending, Sig))
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sigwait (&set, nullptr);
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#endif
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}
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sigprocmask (SIG_UNBLOCK, &set, nullptr);
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}
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#else
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signal (Sig, m_osig);
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#endif
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}
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DISABLE_COPY_AND_ASSIGN (scoped_ignore_signal);
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private:
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#ifdef HAVE_SIGPROCMASK
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bool m_was_blocked;
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#else
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sighandler_t m_osig;
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#endif
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};
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struct scoped_ignore_signal_nop
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{
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/* Note, these can't both be "= default", because otherwise the
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compiler warns that variables of this type are not used. */
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scoped_ignore_signal_nop ()
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{}
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~scoped_ignore_signal_nop ()
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{}
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DISABLE_COPY_AND_ASSIGN (scoped_ignore_signal_nop);
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};
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#ifdef SIGPIPE
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using scoped_ignore_sigpipe = scoped_ignore_signal<SIGPIPE, true>;
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#else
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using scoped_ignore_sigpipe = scoped_ignore_signal_nop;
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#endif
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#endif /* SCOPED_IGNORE_SIGNAL_H */
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