System V and SIGCLD

[Nigel Holder Marconi]

   The problem with resetng SIGCLD is that the signal is still valid since
the child process is waiting for the parent to perform a wait.  The following
implements this and of course works !



	trap(sig)

	int	sig;

	{
		int	c;

		printf("trapped SIGCLD\n");
		wait(&c);
		signal(SIGCLD, trap);	/* reset handler */
	}


   Now that brings me to wait.  4.2 at least provides two flavours of wait :
wait and wait3.  Now wait3 is new and is free to do what it wants in its own
way.   Wait however, does not requires an int pointer, it requires a pointer
to a union which happens to start with an int.  Whether this affects
programs written in Sys V flavour or not is probably well defined at the
moment, but it could change.  Just another example of a transparent
difference between flavours that is easily overlooked.