Date: Sat, 09 Feb 2013 11:08:46 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Christoph Mallon <christoph.mallon@gmx.de> Cc: Kirk McKusick <mckusick@mckusick.com>, freebsd-arch@FreeBSD.org Subject: Re: Proposal: Unify printing the function name in panic messages() Message-ID: <5116121E.1010601@FreeBSD.org> In-Reply-To: <51160E06.1070404@gmx.de> References: <51141E33.4080103@gmx.de> <511426B8.2070800@FreeBSD.org> <51160E06.1070404@gmx.de>
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on 09/02/2013 10:51 Christoph Mallon said the following:
> On 07.02.2013 23:12, Andriy Gapon wrote:
>> on 07/02/2013 23:35 Christoph Mallon said the following:
>>> panic("just a message");
>>
>> This seems perfect.
>> Panic without at least a stack trace or preferably a crash dump is practically
>> useless in most cases. A stack trace already has all the function names.
>> So a function name in a message seems to be redundant.
>
> This is nice in theory, but infeasible in practice.
> More than half of the panic() calls include the correct function name in a way or another.
> I estimate, that another quarter show a wrong name.
In any case, you just search the code for the message and that's it.
I don't suppose that there are many duplicates there.
> It is hard to get this number mechanically, because, well, the names are wrong.
> So most calls include the name (or try to).
> Having no function name is a minority.
> I plan to correct and unify this hotchpotch.
> Also, if stack traces are disabled, you at least can reliably determine, where the panic came from.
Even if you can determine that, without more debugging data that would be
useless in most cases. (We paniced because something went wrong, but why did it
happen?)
> Finally, you can turn the names on and off with one central switch.
Well, have you experienced any problems with debugging due to those
(absent/misleading) function names? Or do you see many reports about such problems?
If this is a solution in search of a problem, then I don't like it, because it
requires massive, if mostly mechanical, changes throughout the code.
If panic message like ("invalid value of bar") were to be changed to something
like ("invalid value of bar (%foo)", bar) I would find that to be a far more
useful project.
--
Andriy Gapon
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