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gdb: fall back on sigpending + sigwait if sigtimedwait is not available

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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>
This commit is contained in:
Simon Marchi
2021-07-05 09:56:10 -04:00
parent 507af45f62
commit fa8740b675
2 changed files with 19 additions and 2 deletions
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6
gdbsupport/ChangeLog
View File

@@ -1,3 +1,9 @@
2021-07-05 Simon Marchi <simon.marchi@polymtl.ca>
* scoped_ignore_signal.h (struct scoped_ignore_signal)
<~scoped_ignore_signal>: Use sigtimedwait if HAVE_SIGTIMEDWAIT
is defined, else use sigpending + sigwait.
2021-07-05 Simon Marchi <simon.marchi@polymtl.ca>
* common.m4 (GDB_AC_COMMON): Check for sigtimedwait.

15
gdbsupport/scoped_ignore_signal.h
View File

@@ -58,7 +58,6 @@ public:
if (!m_was_blocked)
{
sigset_t set;
const timespec zero_timeout = {};
sigemptyset (&set);
sigaddset (&set, Sig);
@@ -66,7 +65,19 @@ public:
/* If we got a pending Sig signal, consume it before
unblocking. */
if (ConsumePending)
sigtimedwait (&set, nullptr, &zero_timeout);
{
#ifdef HAVE_SIGTIMEDWAIT
const timespec zero_timeout = {};
sigtimedwait (&set, nullptr, &zero_timeout);
#else
sigset_t pending;
sigpending (&pending);
if (sigismember (&pending, Sig))
sigwait (&set, nullptr);
#endif
}
sigprocmask (SIG_UNBLOCK, &set, nullptr);
}