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Windows does not have POSIX-like signals, and so we ignore all
operations on the non-existent signal mask machinery.
Do not turn sigemptyset into a function, but leave it a macro that
erases the code in the argument because it is used to set sa_mask
of a struct sigaction, but our dummy in mingw.h does not have that
member.
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Blocked and ignored signals -- but not caught signals -- are inherited
across exec. Some callers with sloppy signal-handling behavior can call
git with SIGPIPE blocked or ignored, even non-deterministically. When
SIGPIPE is blocked or ignored, several git commands can run indefinitely,
ignoring EPIPE returns from write() calls, even when the process that
called them has gone away. Our specific case involved a pipe of git
diff-tree output to a script that reads a limited amount of diff data.
In an ideal world, git would never be called with SIGPIPE blocked or
ignored. But in the real world, several real potential callers, including
Perl, Apache, and Unicorn, sometimes spawn subprocesses with SIGPIPE
ignored. It is easier and more productive to harden git against this
mistake than to clean it up in every potential parent process.
Signed-off-by: Patrick Reynolds <patrick.reynolds@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The test case depends on that test-sigchain can commit suicide by a
call to raise(SIGTERM) in a way that run-command.c::wait_or_whine()
can detect as death through a signal. There are no POSIX signals on
Windows, and a sufficiently close emulation is not available in the
Microsoft C runtime (and probably not even possible).
The particular deficiency is that when a signal is raise()d whose
SIG_DFL action will cause process death (SIGTERM in this case), the
implementation of raise() in msvcrt just calls exit(3).
We could check for exit code 3 in addition to 143, but that would
miss the point of the test entirely. Hence, just skip it on Windows.
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a sub-process dies with a signal, we convert the exit
code to the shell convention of 128+sig. Callers of git may
be relying on this behavior, so let's make sure it does not
break.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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ksh93 is known to report $? of programs that terminated by a signal as
256 + signal number instead of 128 + signal number like other POSIX
compliant shells (ksh's behavior is still POSIX compliant in this regard).
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The signal tests consists of checking that each of our
handlers is executed, and that the test program was killed
by the final signal. We arbitrarily used SIGINT as the kill
signal.
However, some platforms (notably Solaris) will default
SIGINT to SIG_IGN if there is no controlling terminal. In
that case, we don't end up killing the program with the
final signal and the test fails.
This is a problem since the test script should not depend
on outside factors; let's use SIGTERM instead, which should
behave consistently.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If a piece of code wanted to do some cleanup before exiting
(e.g., cleaning up a lockfile or a tempfile), our usual
strategy was to install a signal handler that did something
like this:
do_cleanup(); /* actual work */
signal(signo, SIG_DFL); /* restore previous behavior */
raise(signo); /* deliver signal, killing ourselves */
For a single handler, this works fine. However, if we want
to clean up two _different_ things, we run into a problem.
The most recently installed handler will run, but when it
removes itself as a handler, it doesn't put back the first
handler.
This patch introduces sigchain, a tiny library for handling
a stack of signal handlers. You sigchain_push each handler,
and use sigchain_pop to restore whoever was before you in
the stack.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Johannes Sixt
Patrick Reynolds
Jeff King