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Re: Unbearably slow editing in .h files
Re: Unbearably slow editing in .h files
Thu, 3 Apr 2008 17:58:42 +0000
On Thu, Apr 03, 2008 at 08:22:10AM -0700, Dan Nicolaescu wrote:
> Alan Mackenzie <address@hidden> writes:
> > On Thu, Apr 03, 2008 at 06:10:40AM -0700, Dan Nicolaescu wrote:
> > > Alan Mackenzie <address@hidden> writes:
> > > > On Wed, Apr 02, 2008 at 04:47:52PM -0700, Dan Nicolaescu wrote:
> > > Note that `diff-add-change-log-entries-other-window' is C-x 4 A not
> > > C-x 4 a, it is the equivalent of:
> > > FOR each hunk in a diff DO
> > > C-x 4 a
> > Wow! I've just tried this. It's amazing! There are one or two
> > things in it which aren't quite right, though.
> Yep, it should not generate duplicate entries. One possible
> improvement is that it should iterate at a lower granularity than a
> hunk, some hunks have changes ! + and - changes. (but that's still not
> enough, a + hunk could be adding 5 functions...)
I tried it (with a window configuration I can't remember exactly) and
ChangeLog ended up in both the upper and lower windows. But that's for
another thread. ;-)
> > > When used on a diff buffer with thousands of lines, it is a bit
> > > slow.
> > Hmmm. I've only tried it on diffs with elisp files. That was a
> > little slow. Do you mean it's _very_ slow with C file diffs? Can
> > you give some numbers here? Processor speed, size of diff file,
> > time it takes.
> Unfortunately I don't have any massive patches handy, so I can't test
> now how much things have improved for exactly the things that had
> problems before. But some quick tests with the diff for lisp.h
> revision 1.606 (i.e. something that had a long ChangeLog entry, 625
> lines unidiff) showed that things have improved quite a lot today vs a
> > 1 month old emacs (a few seconds vs > 2 minutes). Which is great.
> Trying C-x 4 A on a 4-5000 lines patch would be more interesting...
> > But then again, people are only going to be using it once or twice
> > per patch (and then having to fill out the result by hand), so it
> > is surely not that critical. But if it were taking 20 minutes
> > rather than 45 seconds, that would be too slow, I agree.
> Ideally in the future C-x 4 A should be done automatically when doing a
> checkin, that why it is important to be as fast as possible.
I'm not sure I agree, here. That might make it far too easy for people
to forget (or even to "forget") to write commit comments.
> > > > To the extent that it's still slower than it might be, yes
> > > > it's the K&R stuff making it slow. The function which takes
> > > > time is c-in-knr-argdecl (cc-engine.el, ~L6317). Actually,
> > > > this function gets called twice. It would take a lot of
> > > > refactoring to make it get called only once.
> > > What if it's not called at all? After all, the vast majority of
> > > the users never edit K&R. Just a thought...
> > Well, one set of users who still use K&R is the Emacs development
> > team. ;-)
> Yeah, and many people wish that would change at some point. But that a
> separate discussion that we should get into now.
I'm not sure why we don't just change all the K&R declarations to ANSI
ones. It could probably be done simply enough with a script (awk, perl,
python, Emacs Lisp, or anything else).
> > It would be possible, and very easy, to make K&R a user option.
> > But I don't think that's the right thing to do.
> > The overhead that K&R imposes on C-M-a and C-x 4 a is not _that_
> > high, and it will diminish as processors continue to get faster. I
> > recently put in a hard-coded limit to the number of parameter
> > declarations in a K&R section. That limit is currently 20.
> Just exploring options here...
> Would simply ignoring K&R for the purpose of running C-x 4 a work?
No. You're at the opening brace of a C function/typedef/struct; you've
got, somehow, to get from there to the function name. That involves
jumping backwards over the K&R region, should it be present. Or, point
starts out _outside_ a brace block. You've got to decide whether it's
inside a function/typedef/struct header, and this might be the K&R
> Yes, it might generate the wrong name in the ChangeLog entry in some
> very limited cases (is that true?), .....
I doubt it. I think it would foul up with _every_ K&R function
declaration. To try it out, set the major mode to C++ mode, then try
C-M-a or C-x 4 a. In fact, in xdisp.c, I've just done this, gone to EOB
and typed C-M-a 25 times. It got BOD OK 8 times, failed 17 times.
> ...., but that's not very critical.
I think it would be. It would only need to happen to a hacker once, and
he would lose all confidence in it. He would then feel obliged to check
every entry by hand - and the complaints would find their way to
Alan Mackenzie (Nuremberg, Germany).