Re: [PATCH 1/1] emacs: always write emacs/.eldeps when the target is remade

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+       Thu, 13 Feb 2014 09:26:43 +0200 (EET)\r
+From: Tomi Ollila <tomi.ollila@iki.fi>\r
+To: Austin Clements <amdragon@MIT.EDU>\r
+Subject: Re: [PATCH 1/1] emacs: always write emacs/.eldeps when the target is\r
+       remade\r
+In-Reply-To: <20140213071026.GX4375@mit.edu>\r
+References: <1390645309-2326-1-git-send-email-tomi.ollila@iki.fi>\r
+       <20140213071026.GX4375@mit.edu>\r
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+Date: Thu, 13 Feb 2014 09:26:43 +0200\r
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+On Thu, Feb 13 2014, Austin Clements <amdragon@MIT.EDU> wrote:\r
+\r
+> Quoth Tomi Ollila on Jan 25 at 12:21 pm:\r
+>> So that the target is newer than its prerequisites.\r
+>> ---\r
+>>  emacs/Makefile.local | 3 +--\r
+>>  1 file changed, 1 insertion(+), 2 deletions(-)\r
+>> \r
+>> diff --git a/emacs/Makefile.local b/emacs/Makefile.local\r
+>> index 42bfbd9..d5d402e 100644\r
+>> --- a/emacs/Makefile.local\r
+>> +++ b/emacs/Makefile.local\r
+>> @@ -32,8 +32,7 @@ emacs_bytecode = $(emacs_sources:.el=.elc)\r
+>>  ifeq ($(HAVE_EMACS),1)\r
+>>  $(dir)/.eldeps: $(dir)/Makefile.local $(dir)/make-deps.el $(emacs_sources)\r
+>>     $(call quiet,EMACS) --directory emacs -batch -l make-deps.el \\r
+>> -           -f batch-make-deps $(emacs_sources) > $@.tmp && \\r
+>> -           (cmp -s $@.tmp $@ || mv $@.tmp $@)\r
+>> +           -f batch-make-deps $(emacs_sources) > $@.tmp && mv $@.tmp $@\r
+>>  -include $(dir)/.eldeps\r
+>>  endif\r
+>>  CLEAN+=$(dir)/.eldeps $(dir)/.eldeps.tmp\r
+>\r
+> Is this just so the rule doesn't get run again on the next make\r
+> invocation (unless, of course, a dependent changed)?\r
+\r
+Basically yes. I did multiple builds in rapid succession when developing\r
+something and this thing confused me quite a lot in the beginning...\r
+\r
+> Interestingly, if any of the dependents have changed, but in ways that\r
+> don't affect .eldeps, this change will make the build more expensive\r
+> because it will trigger a make restart after .eldeps is updated.\r
+\r
+I wondered what was the reason for the recipe you've chosen here, has\r
+it something to do with inodes or something ;) (and were going to ask\r
+an alternative to touch (or even : > $@) the target...\r
+\r
+... but now I understand. E.g. change in notmuch-lib.el will cause *all* \r
+.el files to be re-bytecompiled after this change. \r
+\r
+An alternative to this patch would be adding a message to the rule\r
+which informs user to touch .eldeps to avoid re-doing .eldeps if\r
+that irritates one :D\r
+\r
+something like:\r
+\r
+(cmp -s $@.tmp $@ && \\r
+     echo "touch $@ to avoid redoing this target" || mv $@.tmp $@)\r
+\r
+Thanks, \r
+\r
+Tomi\r