On Fri, Jul 15, 2016 at 11:19:23AM -0700, Junio C Hamano wrote:
> Jeff King <peff@xxxxxxxx> writes:
>
> > + /*
> > + * If non-zero, send error messages to this descriptor rather
> > + * than stderr. The descriptor is closed before check_connected
> > + * returns.
> > + */
> > + int err_fd;
>
> Theoretically speaking it may be possible that a caller may want to
> write to fd#0 if it closed the standard input before creating the
> output channel for multiplexing into a sideband, but I think this
> design strikes a good balance between the theoretical correctness
> and usability. Using err_fd == -1 as "no redirect" may allow the
> caller to redirect the errors to fd#0, but that forces normal users
> to explicitly set this field to -1.
Yep, I had all of those thoughts while writing it, but decided that "0"
was worth it to keep the initialization simple (though since we have
CHECK_CONNECTED_INIT, the "-1" would only have to appear there).
What decided me were two things:
- directing to fd#0 really is theoretical; you'd have to close stdin,
and you shouldn't do that. You should redirect it from /dev/null
(and our sanitize_stdfds() makes sure that we're not surprised by
any callers)
- "struct child_process" uses a similar zero-initialization
-Peff
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