Re: Why does zsh un-ignores SIGQUIT?

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

On Wed, 2019-04-24 at 09:13 +0100, Stephane Chazelas wrote:
> $ (trap '' QUIT; grep SigIgn /proc/self/status; ./Src/zsh -c 'grep SigIgn /proc/self/status')
> SigIgn: 0000000000000004
> SigIgn: 0000000000000000
> 
> That only seems to be happening for SIGQUIT.
> 
> (that's from the current git HEAD)

SIGQUIT is ignored internally within the shell, visible below the patched
code.  The shell knows if you've explicitly ignored SIGQUIT, but not if
it's ignored by inheritance when the shell starts.  The flag is tested
in entersubsh().

pws

diff --git a/Src/init.c b/Src/init.c
index e7e62e2f7..2d5c3296d 100644
--- a/Src/init.c
+++ b/Src/init.c
@@ -1234,6 +1234,15 @@ init_signals(void)
 
     intr();
 
+#ifdef POSIX_SIGNALS
+    {
+	struct sigaction act;
+	if (!sigaction(SIGQUIT, NULL, &act) &&
+	    act.sa_handler == SIG_IGN)
+	    sigtrapped[SIGQUIT] = ZSIG_IGNORED;
+    }
+#endif
+
 #ifndef QDEBUG
     signal_ignore(SIGQUIT);
 #endif