Subject: Re: [PATCH] ref-filter: initialize empty name or email fields

From: Mischa POSLAWSKY <[email-masked]>
Date: Thu, 22 Aug 2019 15:23:34 +0200

Junio wrote:
> Junio C Hamano <[email-masked]> writes:
> 
> > Mischa POSLAWSKY <[email-masked]> writes:
> >
> >> Formatting $(taggername) on headerless tags such as v0.99 in Git
> >> causes a SIGABRT with error "munmap_chunk(): invalid pointer",
> >> because of an oversight in commit f0062d3b74 (ref-filter: free
> >> item->value and item->value->s, 2018-10-19).
> >>
> >> Signed-off-by: Mischa POSLAWSKY <[email-masked]>
> >> ---
> >> If I understand correctly, such tags cannot be produced normally anymore.
> >> Therefore I'm unsure how to make tests, and if that is even warranted.
> >
> > Thanks for spotting.
> >
> > I am not sure if the approach taken by this patch is the right one,
> > though.  I didn't follow the call/dataflow thoroughly, but if we
> > replace unfree-able "" with NULL in these places, wouldn't
> > fill_missing_values() take care of them?
> 
> I think replacing these "" with NULL would be safe, but there are
> many places that return xstrdup("") from inside the callees of
> populate_value(), so the patch presented here would be more
> consistent with the current practice, I think.

Indeed, I just copied the existing style.  Returning NULL seems to work,
but not something I'm confident to clean up here.

> So let's take the patch as is, at least for now.  Thanks.

Thank you!

> >>  ref-filter.c | 6 +++---
> >>  1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/ref-filter.c b/ref-filter.c
> >> index f27cfc8c3e..7338cfc671 100644
> >> --- a/ref-filter.c
> >> +++ b/ref-filter.c
> >> @@ -1028,7 +1028,7 @@ static const char *copy_name(const char *buf)
> >>  		if (!strncmp(cp, " <", 2))
> >>  			return xmemdupz(buf, cp - buf);
> >>  	}
> >> -	return "";
> >> +	return xstrdup("");
> >>  }
> >>  
> >>  static const char *copy_email(const char *buf)
> >> @@ -1036,10 +1036,10 @@ static const char *copy_email(const char *buf)
> >>  	const char *email = strchr(buf, '<');
> >>  	const char *eoemail;
> >>  	if (!email)
> >> -		return "";
> >> +		return xstrdup("");
> >>  	eoemail = strchr(email, '>');
> >>  	if (!eoemail)
> >> -		return "";
> >> +		return xstrdup("");
> >>  	return xmemdupz(email, eoemail + 1 - email);
> >>  }