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926ac872e9
I tried building GDB on GNU/Hurd, and ran into this warning:
gdbsupport/scoped_ignore_signal.h:78:16: error: null argument where non-null required (argument 2) [-Werror=nonnull]
This is because in this commit:
commit 99624310dd
Date: Sun Jun 27 15:13:14 2021 -0400
gdb: fall back on sigpending + sigwait if sigtimedwait is not available
A call to sigwait was introduced that passes nullptr as the second
argument, this call is only reached if sigtimedwait is not supported.
The original patch was written for macOS, I assume on that target
passing nullptr as the second argument is fine.
On my GNU/Linux box, the man-page for sigwait doesn't mention that
nullptr is allowed for the second argument, so my assumption would be
that nullptr is not OK, and, if I change the '#ifdef
HAVE_SIGTIMEDWAIT' introduced by the above patch to '#if 0', and
rebuild on GNU/Linux, I see the same warning that I see on GNU/Hurd.
I propose that we stop passing nullptr as the second argument to
sigwait, and instead pass a valid int pointer. The value returned in
the int can then be used in an assert.
For testing, I (locally) made the change to the #ifdef I mentioned
above, compiled GDB, and ran the usual tests, this meant I was using
sigwait instead on sigtimedwait on GNU/Linux, I saw no regressions.
122 lines
3.1 KiB
C++
122 lines
3.1 KiB
C++
/* Support for ignoring signals.
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Copyright (C) 2021-2022 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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{
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int sig_found;
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sigwait (&set, &sig_found);
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gdb_assert (sig_found == Sig);
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}
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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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