From: Paolo Bonzini <pbonzini@redhat.com>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: Markus Armbruster <armbru@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>
Subject: [Qemu-devel] Re: [PATCH 2/2] trace: avoid unnecessary recompilation if nothing changed
Date: Mon, 27 Sep 2010 18:16:55 +0200 [thread overview]
Message-ID: <4CA0C377.2080806@redhat.com> (raw)
In-Reply-To: <AANLkTimPYni2UHVqu0D5TbY7jnAYbdYXRNN-H6bqL2tt@mail.gmail.com>
On 09/27/2010 06:13 PM, Blue Swirl wrote:
>> Indeed, see how it's done for config-*.h.
>>
>> # Uses generic rule in rules.mak
>> trace.h: trace.h-timestamp
>> trace.h-timestamp: $(SRC_PATH)/trace-events config-host.mak
>> $(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -h< $< > $@," GEN trace.h)
>> @cmp $@ trace.h>/dev/null 2>&1 || cp $@ trace.h
>>
>> (untested).
>
> I just copied the rule from %/config-devices.mak. Is also that rule
> then incorrect?
config-devices.mak will cause the Makefile to be reread, but no
recompilations, so it's fine not to use a timestamp file. Headers are
more complicated.
> Perhaps there could be a macro for this, not unlike move-if-change
> script in various GNU packages?
The problem is not really the move-if-change script, but rather the
timestamping rules. You can use $(eval) for that but it quickly becomes
unmanageable.
Paolo
next prev parent reply other threads:[~2010-09-27 16:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-26 9:05 [Qemu-devel] [PATCH 2/2] trace: avoid unnecessary recompilation if nothing changed Blue Swirl
2010-09-26 16:15 ` Stefan Hajnoczi
2010-09-27 8:32 ` Markus Armbruster
2010-09-27 9:51 ` [Qemu-devel] " Paolo Bonzini
2010-09-27 16:13 ` Blue Swirl
2010-09-27 16:16 ` Paolo Bonzini [this message]
2010-09-28 8:58 ` [Qemu-devel] " Markus Armbruster
2010-09-29 11:42 ` [Qemu-devel] " Paolo Bonzini
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