Return-Path: X-Original-To: notmuch@notmuchmail.org Delivered-To: notmuch@notmuchmail.org Received: from localhost (localhost [127.0.0.1]) by olra.theworths.org (Postfix) with ESMTP id 45829431FC2 for ; Wed, 19 Feb 2014 12:48:04 -0800 (PST) X-Virus-Scanned: Debian amavisd-new at olra.theworths.org X-Spam-Flag: NO X-Spam-Score: 0 X-Spam-Level: X-Spam-Status: No, score=0 tagged_above=-999 required=5 tests=[none] autolearn=disabled Received: from olra.theworths.org ([127.0.0.1]) by localhost (olra.theworths.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id joXR-w6iEAcP for ; Wed, 19 Feb 2014 12:47:56 -0800 (PST) Received: from guru.guru-group.fi (guru.guru-group.fi [46.183.73.34]) by olra.theworths.org (Postfix) with ESMTP id 764CA431FBF for ; Wed, 19 Feb 2014 12:47:56 -0800 (PST) Received: from guru.guru-group.fi (localhost [IPv6:::1]) by guru.guru-group.fi (Postfix) with ESMTP id 1BD8010005E; Wed, 19 Feb 2014 22:47:50 +0200 (EET) From: Tomi Ollila To: Austin Clements Subject: Re: [PATCH 1/1] emacs: always write emacs/.eldeps when the target is remade In-Reply-To: <20140219195457.GD13537@mit.edu> References: <1390645309-2326-1-git-send-email-tomi.ollila@iki.fi> <20140213071026.GX4375@mit.edu> <20140213074944.GY4375@mit.edu> <20140214215736.GD4375@mit.edu> <20140219195457.GD13537@mit.edu> User-Agent: Notmuch/0.17+69~g761b031 (http://notmuchmail.org) Emacs/24.3.1 (x86_64-unknown-linux-gnu) X-Face: HhBM'cA~ MIME-Version: 1.0 Content-Type: text/plain Cc: notmuch@notmuchmail.org X-BeenThere: notmuch@notmuchmail.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Use and development of the notmuch mail system." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Feb 2014 20:48:04 -0000 On Wed, Feb 19 2014, Austin Clements wrote: > Quoth myself on Feb 14 at 4:58 pm: >> Quoth Tomi Ollila on Feb 14 at 9:24 pm: >> > On Thu, Feb 13 2014, Austin Clements wrote: >> > >> > > Quoth Tomi Ollila on Feb 13 at 9:26 am: >> > >> On Thu, Feb 13 2014, Austin Clements wrote: >> > >> >> > >> > Quoth Tomi Ollila on Jan 25 at 12:21 pm: >> > >> >> So that the target is newer than its prerequisites. >> > >> >> --- >> > >> >> emacs/Makefile.local | 3 +-- >> > >> >> 1 file changed, 1 insertion(+), 2 deletions(-) >> > >> >> >> > >> >> diff --git a/emacs/Makefile.local b/emacs/Makefile.local >> > >> >> index 42bfbd9..d5d402e 100644 >> > >> >> --- a/emacs/Makefile.local >> > >> >> +++ b/emacs/Makefile.local >> > >> >> @@ -32,8 +32,7 @@ emacs_bytecode = $(emacs_sources:.el=.elc) >> > >> >> ifeq ($(HAVE_EMACS),1) >> > >> >> $(dir)/.eldeps: $(dir)/Makefile.local $(dir)/make-deps.el $(emacs_sources) >> > >> >> $(call quiet,EMACS) --directory emacs -batch -l make-deps.el \ >> > >> >> - -f batch-make-deps $(emacs_sources) > $@.tmp && \ >> > >> >> - (cmp -s $@.tmp $@ || mv $@.tmp $@) >> > >> >> + -f batch-make-deps $(emacs_sources) > $@.tmp && mv $@.tmp $@ >> > >> >> -include $(dir)/.eldeps >> > >> >> endif >> > >> >> CLEAN+=$(dir)/.eldeps $(dir)/.eldeps.tmp >> > >> > >> > >> > Is this just so the rule doesn't get run again on the next make >> > >> > invocation (unless, of course, a dependent changed)? >> > >> >> > >> Basically yes. I did multiple builds in rapid succession when developing >> > >> something and this thing confused me quite a lot in the beginning... >> > >> >> > >> > Interestingly, if any of the dependents have changed, but in ways that >> > >> > don't affect .eldeps, this change will make the build more expensive >> > >> > because it will trigger a make restart after .eldeps is updated. >> > >> >> > >> I wondered what was the reason for the recipe you've chosen here, has >> > >> it something to do with inodes or something ;) (and were going to ask >> > >> an alternative to touch (or even : > $@) the target... >> > >> >> > >> ... but now I understand. E.g. change in notmuch-lib.el will cause *all* >> > >> .el files to be re-bytecompiled after this change. >> > > >> > > This is unrelated to the cmp in the recipe. A change in >> > > notmuch-lib.el *must* cause almost all .el files to be recompiled >> > > because they almost all require it and may use macros from it. If you >> > > touch, e.g., notmuch-hello.el, you'll see that very little is rebuilt >> > > (with or without this patch). >> > > >> > >> An alternative to this patch would be adding a message to the rule >> > >> which informs user to touch .eldeps to avoid re-doing .eldeps if >> > >> that irritates one :D >> > >> >> > >> something like: >> > >> >> > >> (cmp -s $@.tmp $@ && \ >> > >> echo "touch $@ to avoid redoing this target" || mv $@.tmp $@) >> > > >> > > I think this patch is good as it is; I was just pointing out that the >> > > change also has a performance drawback in some situations. (Knowing >> > > make, there's probably *some* way to get the best of both worlds and >> > > it's probably really ugly.) >> > >> > Ah, now I understand, because emacs/Makefile.local includes emacs/.eldeps >> > when it notices mtime of emacs/.eldeps changes it restarts itself... >> > >> > ... to compare with current behaviour: >> > >> > $ make >> > ... >> > $ touch emacs/notmuch.el >> > $ make >> > ... >> > $ make >> > Use "make V=1" to see the verbose compile lines. >> > EMACS emacs/.eldeps >> > make: Nothing to be done for `all'. >> > $ make >> > Use "make V=1" to see the verbose compile lines. >> > EMACS emacs/.eldeps >> > make: Nothing to be done for `all'. >> > $ make >> > Use "make V=1" to see the verbose compile lines. >> > EMACS emacs/.eldeps >> > make: Nothing to be done for `all'. >> > >> > It will rerun emacs -L emacs -batch -l make-deps.el -f batch-make-deps ... >> > over and over again... >> > >> > I thought I figured out a solution involving .eldeps.stamp file but >> > that turned out to be no-go... (circular dependency netween .eldeps.stamp >> > and Makefile.local). >> > >> > So, with this if one edits emacs/* files and keeps building byte-compiled >> > versions often, make will both run EMACS emacs/.eldeps and restarting >> > -- and when moving to edit other files both of the above stops. Without >> > this change after editing emacs/* files EMACS emacs/.eldeps will be >> > executed until it is touched or make clean executed (I wonder how make >> > handles rebuilding emacs/.eldeps while doing make clean ;) >> > >> > >> > Tomi >> >> Here's a way that works, but it's more complicated than your patch and >> doesn't seem to perform any better: >> >> diff --git a/emacs/Makefile.local b/emacs/Makefile.local >> index 42bfbd9..8a1f1c2 100644 >> --- a/emacs/Makefile.local >> +++ b/emacs/Makefile.local >> @@ -29,14 +29,28 @@ emacs_bytecode = $(emacs_sources:.el=.elc) >> # the byte compiler may load an old .elc file when processing a >> # "require" or we may fail to rebuild a .elc that depended on a macro >> # from an updated file. >> +# >> +# We do this in two rules. .eldeps is the "real" dependencies file >> +# and will be rebuilt if and only if a .el source file changes. We >> +# could include this directly, but then whenever a .el file changed >> +# (and .eldeps's mtime changed), make would restart immediately after >> +# the include below. To avoid this, we create a second file, >> +# .eldeps.x, that we only update when its *contents* differ from >> +# .eldeps. .eldeps will often have an mtime older than .eldeps.x (any >> +# .el file change that does not change dependencies will cause this), >> +# so the .eldeps.x rule will often run, but it executes quickly and >> +# quietly and will not trigger a make restart unless the dependencies >> +# actually change. > > Here's a version of this comment that gets to the point directly: > > # We could include .eldeps directly, but that would cause a make > # restart whenever any .el file was modified, even if dependencies > # didn't change, because the mtime of .eldeps will change. Instead, > # we include a second file, .eldeps.x, which we ensure always has the > # same content as .eldeps, but its mtime only changes when dependency > # information changes, in which case a make restart is necessary > # anyway. I think this behaviour is tolerable: instead of verbosely re-run emacs to re-create .eldeps every time just to see the new .eldeps is not going to be used we just silently re-run only lightweight cmp. Tomi > >> ifeq ($(HAVE_EMACS),1) >> $(dir)/.eldeps: $(dir)/Makefile.local $(dir)/make-deps.el $(emacs_sources) >> $(call quiet,EMACS) --directory emacs -batch -l make-deps.el \ >> -f batch-make-deps $(emacs_sources) > $@.tmp && \ >> - (cmp -s $@.tmp $@ || mv $@.tmp $@) >> --include $(dir)/.eldeps >> + mv $@.tmp $@ >> +$(dir)/.eldeps.x: $(dir)/.eldeps >> + @cmp -s $^ $@ || cp $^ $@ >> +-include $(dir)/.eldeps.x >> endif >> -CLEAN+=$(dir)/.eldeps $(dir)/.eldeps.tmp >> +CLEAN+=$(dir)/.eldeps $(dir)/.eldeps.tmp $(dir)/.eldeps.x >> >> ifeq ($(HAVE_EMACS),1) >> %.elc: %.el $(global_deps) > _______________________________________________ > notmuch mailing list > notmuch@notmuchmail.org > http://notmuchmail.org/mailman/listinfo/notmuch