Re: [PATCH] t4062: stop using repetition in regex

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 8, 2017, 22:26 UTC
Message-ID: <xmqq7eydae7r.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <xmqqinhxaf0i.fsf@gitster.mtv.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 12 quoted lines

> So I find Dscho's concern quite valid, even though I do believe you
> when you say the code somehow segfaults.  I just can not tell
> how/why it would segfault, though---it is possible that regexec()
> implementation is stupid and does not realize that it can return early
> reporting success without looking at the rest of the buffer, but
> somehow I find it unlikely.
>
> Puzzled.
>
>> You get different results?  How is that possible?  The search string is
>> NUL-terminated in each case, while the point of the test is that the
>> file contents isn't, right?

Intellectual curiosity tells me we may want to find out why it fails, but in the meantime, I think replacing the test with "0$" to force the scanner to find either the end of line or the end of the buffer may be a good workaround. We do not have to care how many of random bytes are in front of the last "0" in order to ensure that the regexec_buf() does not overstep to 4097th byte, while seeing that regexec() that does not know how long the haystack is has to do so, no?