Re: [PATCH] transport-helper.c: don't leak fdopen'd stream buffers

[Johannes Sixt <j6t@kdbg.org>]

On Sonntag, 13. September 2009, Junio C Hamano wrote:
> Jim Meyering <jim@meyering.net> writes:
> > diff --git a/transport-helper.c b/transport-helper.c
> > index f57e84c..0bbd014 100644
> > --- a/transport-helper.c
> > +++ b/transport-helper.c
> > @@ -49,6 +49,7 @@ static struct child_process *get_helper(struct
> > transport *transport) if (!strcmp(buf.buf, "fetch"))
> >  			data->fetch = 1;
> >  	}
> > +	fclose (file);
> >  	return data->helper;
> >  }
> >
> > @@ -88,6 +89,7 @@ static int fetch_with_fetch(struct transport
> > *transport, if (strbuf_getline(&buf, file, '\n') == EOF)
> >  			exit(128); /* child died, message supplied already */
> >  	}
> > +	fclose (file);
> >  	return 0;
> >  }
>
> The callchain of fetch_with_fetch() looks like:
>
>     fetch_with_fetch()
>         helper = get_helper();
>         --> get_helper()
>             - start helper with start_command();
>             - read from helper->out until it sees an empty line;
>             - break out of the loop;
>         <-- return helper
>         - file = xfdopen(helper->out) to get another FILE on the fd
>         - read the rest of the output from helper->out via file
>
> It seems to me that the fclose() in get_helper() will close the underlying
> fd and would break the caller, no?
>
> I think "struct helper_data" should get a new FILE* field and once
> somebody creates a FILE* out of its helper->out, that FILE* can be passed
> around without a new xfdopen().
>
> Or something like that.
>
> Who is responsible for closing the underlying helper->out fd in the
> start_command() API, by the way?

A pipe was requested by setting helper->out = -1 before the call to 
start_command(), and in such a case the caller must close the fd.

-- Hannes