Re: [PATCH] git-svn: workaround for a bug in svn serf backend

From: Thomas Rast <tr@thomasrast.ch>
Date: Dec 30, 2013, 12:20 UTC
Message-ID: <87lhz2o7ht.fsf@thomasrast.ch>
In-Reply-To: <1388059524-4864-1-git-send-email-rkagan@mail.ru>

Roman Kagan <rkagan@mail.ru> writes:

Show 7 quoted lines

> +	# workaround for a bug in svn serf backend (v1.8.5 and below):
> +	# store 3d argument to ->add_file() in a local variable, to make it
> +	# have the same lifetime as $fbat
> +	my $upa = $self->url_path($m->{file_a});
>  	my $fbat = $self->add_file($self->repo_path($m->{file_b}), $pbat,
> -				$self->url_path($m->{file_a}), $self->{r});
> +				$upa, $self->{r});

Hmm, now that you put it that way, I wonder if the patch is correct.

Let me first rephrase the problem to verify that I understand the issue:

  $fbat keeps a pointer to the $upa string, without maintaining a
  reference to it.  When $fbat is destroyed, it needs this string, so we
  must ensure that the lifetime of $upa is at least as long as that of
  $fbat.

However, does Perl make any guarantees as to the order in which local variables are unreferenced and then destroyed? I can't find any such guarantee.

In the absence of such, wouldn't we have to keep $upa in an outer, separate scope to ensure that $fbat is destroyed first?

-- 
Thomas Rast
tr@thomasrast.ch