[MPlayer-dev-eng] [RFC] Makefile copyrights

Wed Jun 18 15:44:18 CEST 2008

On Wed, Jun 18, 2008 at 02:31:34PM +0200, Diego Biurrun wrote:
> On Wed, Jun 18, 2008 at 02:56:37AM +0200, Michael Niedermayer wrote:
> > On Wed, Jun 18, 2008 at 01:27:37AM +0200, Diego Biurrun wrote:
> > > On Tue, Jun 17, 2008 at 07:39:31PM +0200, Michael Niedermayer wrote:
> > > > On Tue, Jun 17, 2008 at 02:57:16PM +0200, Diego Biurrun wrote:
> > > > > On Sat, Jun 07, 2008 at 04:11:34PM +0200, Michael Niedermayer wrote:
> > > > > > 
> > > > > > * Its faster to build a .a per directory and then combine them than collect
> > > > > >   all .o files if one changed. (simple matter of less collecting
> > > >                    ^^^^^^^^^^^^^^
> > > > > >   recompile one c file collect all .o of one dir collect all .a vs.
> > > > > >   recompile one c file collect all .o of the whole project)
> > > > > >   seeks are slow reading lots of files is slower than reading one
> > > > > >   big one ...
> > > > > 
> > > > > This is not true.
> > > > > 
> > > > > I just did a quick benchmark comparing r26339 with HEAD.  I configured
> > > > > both trees with the same options and then ran make in them.  After that
> > > > > I ran 'rm mplayer mencoder' and then 'time make' in both trees in order
> > > > > to benchmark just the last linking step.  Results vary by 0.1 seconds,
> > > > > but both are always around 9.8s.
> > > > 
> > > > Not sure about you, but i do change some c files between running make.
> > > > Also not everything might be in the disk cache like it is in your 
> > > > make; rm mplayer; make
> > > > Id be more interrested in the results with a changed c file and a flushed
> >                                                                 ^^^^^^^^^^^^^
> > > > cache. (and changed means not a change that has been compiled in the past
> >     ^^^^^
> > > > and is in ccache)
> > > 
> > > Once more, this time with ccache disabled.  I do
> > > 
> > > touch libmpdemux/demuxer.c libmpcodecs/vd.c && time make
> > > 
> > > and the results are that HEAD with dependency generation disabled takes
> > > 14s, r26339 takes 15.4s.  Accept it, link times have decreased.
> > 
> > A normal development cycle is to edit a c file run make
> > perform some tests & benchmarks (maybe the regression tests in ffmpeg)
> > these will flush the cache if it hasnt been flushed by the time due to
> > other things running, then goto 1.
> > 
> > Besides, "HEAD with dependency generation disabled"? so you compare the
> > unchanged old build system against the new + some hacks to make it faster?
> 
> I am comparing apples to apples.  Your first claim was that link times
> would increase with the new system.  This is false.

I was speaking about the case with a changed file and not everything in the
cache. Collecting many small .o files takes longer than few big .a.
It may very well be that the old build system did other time consuming things.
I was only considering the current build system with per libmp* .a vs the
single big linking at the end.

[...]
> > > > > > Anyway, everyone rewriting something knows his code is better than before
> > > > > > in every respect. It rarely is though, especially if the old code is the
> > > > > > result of years of bugfixes.
> > > > > 
> > > > > The old build system is not the result of years of bug fixes, but the
> > > > > result of years of hacks.  I had to look at the old VIDIX Makefiles
> > > > > recently, my eyes were bleeding.
> > > > > 
> > > > > Much of the old build system looked like a competition in redundant
> > > > > programming.  r21275 alone removed 435 lines (of about 2000 IIRC)
> > > > > without changing one iota of functionality.
> > > > > 
> > > > > There were always a lot of problems and the solution was to recommend to
> > > > > distclean between every make run.  At some point the build system even
> > > > > did this automatically.
> > > > 
> > > > Well whatever you say, fact is that to do development in ffmpeg & mplayer
> > > > i had to 
> > > > -	$(DEPEND_CMD) > $@
> > > > +	touch $@
> > > > 
> > > > Because it otherwise rebuilds litterally everything when any header is
> > > > changed, even with ccache that is rather slow.
> > > 
> > > Just comment out the last line in the MPlayer Makefile or the last line
> > > of common.mak in FFmpeg, much more effective.
> > > 
> > > > For testing a patch and for the end user what the makefiles do currently
> > > > is fine. For doing actual development it is not.
> > > > If i change a header a dozen times and know that it will only need rebuilding
> > > > of one file iam really a few hours quicker if i rebuild that file instead
> > > > of the distclean equivalent that is done in svn currently.
> > > 
> > > Then comment out a line if you do not like it.  This is hardly asking
> > > much.
> > > 
> > > Anyway, this has no relation to what I said and no relation to linking
> > > once or linking (more or less) per directory.  Automatic dependency
> > > generation is a completely separate issue.
> > 
> > * How to use the new shiny build system?
> > -  comment out the last line in the MPlayer Makefile or the last line
> >    of common.mak in FFmpeg
> > 
> > Glad, its not as hackish anymore as it was in the past.
> 
> It is working correctly now, which it did most definitely *not* do in
> the past.  Also, it now automatically generates dependency information.
> You know, some people do find this useful and this was a requested
> feature.  auto* does it as well.  If you dislike automatic dependency
> information generation, disable it.
> 
> What's your problem?  I don't think commenting out one line is asking
> too much of you, is it?

My problem is that having to comment out lines in a file for normal everyday
work is a very hackish solution.

make mplayer_nodep or any other command line based solution would be alot
cleaner

Developers very well might want to occasionally run a make with full
dependencies when they run into a weird bug which they dont know 
what causes it ...
Having to edit the files to switch the dependencies back on IS hackish.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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