Re: [PATCH-v2/RFC 3/6] xutils: fix ignore-all-space on incomplete line

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 23, 2009, 19:40 UTC
Message-ID: <7vljlauxmk.fsf@alter.siamese.dyndns.org>
In-Reply-To: <alpine.DEB.2.00.0908231110500.29625@GWPortableVCS>

Thell Fowler <git@tbfowler.name> writes:

> Because the flow is much more direct it also makes the test additions to 
> t4015 obsolete as they essentially tested for line end conditions instead 
> of whitespace (like they should have).

Your patch 6/6 that added the tests were useful to find a bug I originally had, which is the one below that is commented out.

Show 14 quoted lines

>> +		/*
>> +		 * If we do not want -b to imply --ignore-space-at-eol
>> +		 * then you would need to add this:
>> +		 *
>> +		 * if (!(flags & XDF_IGNORE_WHITESPACE_AT_EOL))
>> +		 *	return (s1 <= i1 && s2 <= i2);
>> +		 *
>> +		 */
>> +
>
> While it would be nice to have -b and --ignore-space-at-eol be two 
> different options that could be merged together the documentation states 
> that -b ignores spaces at eol, and there are scripts that depend on this 
> behavior.

Also that is how "diff -b" behaves, and that is why I said your tests found a _bug_ in my original. I'll drop the above large comment and replace it with just a "/* -b implies --ignore-space-at-eol */".

Show 11 quoted lines

> Right now the xdl_recmatch() checks three distinct flags before having the 
> opportunity to do the default behavior of a straight diff.  In 
> xdl_hash_record there is an initial check for whitespace flags.
>
> ...
> 	if (flags & XDF_WHITESPACE_FLAGS)
> 		return xdl_hash_record_with_whitespace(data, top, flags);
> ...
>
> Perhaps a similar setup for xdl_rematch() and a 
> xdl_recmatch_with_whitespace() ?

Or we can just move the final else clause up and start the function like this:

	int i1, i2;

	if (!(flags & XDF_WHITESPACE_FLAGS))
 		return s1 == s2 && !memcmp(l1, l2, s1);

	i1 = i2 = 0;
 	if (flags & XDF_IGNORE_WHITESPACE) {
		...

that would get rid of two unnecessary clearing of variables (i1 and i2, even though I suspect that the compiler _could_ optimize them out without such an change), and three flags-bit check in the most common case of not ignoring any whitespaces.

Show 6 quoted lines

> Since your to counter-proposals give the same results, provide safer and 
> faster processing, eliminate the additional test, as well as being easier 
> to read and comprehend I propose a v3 with just those two patches.  I'll 
> be glad to post it, with or without a xdl_recmatch_with_whitespace, if 
> need be.  And should I, or do I need to, add something to the commit (ie: 
> ack, tested, ...) ?

I can amend the counterproposal patches with tests from your 6/6 and add your "Tested-by:" and commit them myself.

> Thank you again for taking the time to look at this change!

Thank _you_ for bringing this issue up in the first place.