Re: SIGCHLD in vfork child context

[Paul Eggert <eggert@cs.ucla.edu>]

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YAMAMOTO Mitsuharu wrote:
> I think resetting the SIGCHLD handler in the vfork child on Darwin is
> still a good thing to do even with the change you installed, if the
> SIGCHLD handler call in such a context is unexpected (and does not
> happen on the other platforms).

Although I'm still not entirely sure we've diagnosed the problem correctly, it 
shouldn't hurt to run that code on macOS, so I installed the attached.

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From 611880e11714007a1b5303eedb89bdfacb0a574a Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sun, 21 May 2017 01:46:44 -0700
Subject: [PATCH] Work around macOS bug with vforked child

* src/callproc.c (call_process) [DARWIN_OS]:
Include workaround for apparent macOS bug.
---
 src/callproc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/callproc.c b/src/callproc.c
index 7c85eed..4cec02b 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -631,6 +631,14 @@ call_process (ptrdiff_t nargs, Lisp_Object *args, int filefd,
 
   if (pid == 0)
     {
+#ifdef DARWIN_OS
+      /* Work around a macOS bug, where SIGCHLD is apparently
+	 delivered to a vforked child instead of to its parent.  See:
+	 http://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00342.html
+      */
+      signal (SIGCHLD, SIG_DFL);
+#endif
+
       unblock_child_signal (&oldset);
 
 #ifdef DARWIN_OS
-- 
2.7.4