Re: [PATCH] Improved error messages when temporary file creation fails

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 8, 2010, 02:01 UTC
Message-ID: <7vpqtdm3a4.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20101207212041.GG25767@bzzt.net>

Arnout Engelen <arnouten@bzzt.net> writes:

Show 20 quoted lines

> Thanks to you and Jonathan again for the feedback.
>
> On Tue, Dec 07, 2010 at 12:56:17PM -0800, Junio C Hamano wrote:
>> > +	char origtemplate[255];
>> > +	strlcpy(origtemplate, template, 255);
>> 
>> Why "255"?
>
> Random - 'i had to choose something'.
>
>> It may happen to be sufficiently large for the current callers, but what
>> provisions if any are made to help the compiler or the runtime protect us
>> from new and broken callers?  Use of strlcpy() there hides the issue from
>> the runtime by avoiding segfault, but it actively harms us by making the
>> code silently behave incorrectly without segfaulting, no?
>
> Only in a small way: when a bigger template is encountered and the mkstemp 
> call succeeds, there is no problem. Only when xmkstemp fails *and* clears the
> template, the diagnostic error message shows a truncated version of the 
> original.

Ah, ok, it seems that I misread the patch. This copy you are making is not used to actually construct the filename used for creating the temporary file, so there is no risk the function misbehaving; we would just give a truncated error report, which is no worse than what we have been giving the users anyway.