Re: SIGCHLD in vfork child context

[YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>]

>>>>> On Tue, 16 May 2017 01:58:37 -0700, Paul Eggert <eggert@cs.ucla.edu> said:

>> It seems that calling waitpid from the SIGCHLD handler results in
>> ECHILD in the vfork child context

> Why is the vfork child process getting a SIGCHLD signal? That process doesn't 
> have any children. Is the macOS kernel simply buggy? If so, I suggest adding a 
> short explanation of the situation to this comment:

>> +    /* Call the SIGCHLD handler in case we have received SIGCHLD in
>> +       the vfork child context.  The signal mask is restored by
>> +       unblock_child_signal below.  */

I'll make the comment for the first hunk more explicit about the
situation:

#ifdef DARWIN_OS
      /* On Darwin, SIGCHLD for status change of a child process can
	 be delivered to the vfork child context.  It will confuse the
	 SIGCHLD handler because waitpid results in ECHILD there.  */
      signal (SIGCHLD, SIG_DFL);
#endif

>> +    (*action.sa_handler) (SIGCHLD);

> No need for the * and the first set of parens. I.e., this is OK:

>      action.sa_handler (SIGCHLD);

> Otherwise, looks OK; thanks.

Thanks for the comments.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp