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

From: Roman Kagan <rkagan@mail.ru>
Date: Dec 27, 2013, 06:09 UTC
Message-ID: <CANiYKX6VA2KvJ_YWYOegb6+VFg_unL96P9qUBthYPFuo9fhAMA@mail.gmail.com>
In-Reply-To: <20131226202805.GV20443@google.com>

2013/12/27 Jonathan Nieder <jrnieder@gmail.com>:

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> Roman Kagan wrote:
>
>> Subversion serf backend in versions 1.8.5 and below has a bug that the
>> function creating the descriptor of a file change -- add_file() --
>> doesn't make a copy of its 3d argument when storing it on the returned
>
> 3d makes me think of 3-dimensional. ;-)  I think you mean third
> (or the abbreviation 3rd).

Indeed.

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>> descriptor.  As a result, by the time this field is used (in
>> transactions of file copying or renaming) it may well be released.
>
> Please describe the symptom so this patch is easy to find when other
> people run into it.

OK

> Do I remember correctly that "... released and scribbled over with a
> new value, causing such-and-such assertion to fire" was what happened?

Exactly.

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>> This patch works around this bug, by storing the value to be passed as
>> the 3d argument to add_file() in a local variable with the same scope as
>> the file change descriptor, making sure their lifetime is the same.
>
> Could this be reproduced with a test script to make sure we don't
> reintroduce the bug again later?  (It's okay if the test only fails on
> machines with the problematic svn version.)

That would need a fairly fancy setup phase, as the bug triggers only on http(s)-accessed svn repositories. I'll take a look if there's something already available in the existing test scripts; writing one from scratch for this specific case is IMO beyond the reasonable effort.

> Modulo the confusing 3-dimensional arguments in comments, the code
> change looks good.

Thanks, I'll adjust the wording and resubmit.

Roman.