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From: Jan Beulich <jbeulich@suse.com>
To: Anthony PERARD <anthony.perard@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [XEN PATCH v3 16/23] xen/build: introduce if_changed and if_changed_rule
Date: Wed, 18 Mar 2020 12:14:40 +0100	[thread overview]
Message-ID: <bab73b8e-5a5d-5183-17a3-37d8eed793e5@suse.com> (raw)
In-Reply-To: <20200318104402.GC4088@perard.uk.xensource.com>

On 18.03.2020 11:44, Anthony PERARD wrote:
> On Wed, Mar 04, 2020 at 04:45:36PM +0100, Jan Beulich wrote:
>> On 26.02.2020 12:33, Anthony PERARD wrote:
>>> The if_changed macro from Linux can record the command used to build a
>>> target then compare it on rebuild. Thus if a command has changed, for
>>> example due to introducing new flags in CFLAGS or due to using a
>>> different compiler, the target will be rebuilt.
>>
>> As to using a different compiler - I suppose this means "a compiler
>> with a different executable name" here? What about me having, say
>> gcc-5 in use, and then updating my system such that a 5.2 based
>> compiler of this name would be upgraded to a 5.4 based one of this
>> same name. If this newer compiler has better capabilities (that we
>> would want to use if available), would this or anything else trigger
>> a rebuild then too?
> 
> I think I should have written "command line" instead of just "command".
> When writing about "different compiler" I was mostly thinking about GCC
> vs clang, not really about versions. I think Linux has something that
> detects when the compiler version changes, but that maybe to only
> trigger kconfig, to regenerate the .config file.
> 
> But as you say, if the newer compiler has better capabilities, and the
> *FLAGS are changed, then that would trigger a rebuild if other
> dependency hasn't changed.

"Would" as in "would", or merely "it would be nice if it did"? I'm
simply not seeing where such a detection would be happening.

Jan

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  reply	other threads:[~2020-03-18 11:14 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-26 11:33 [Xen-devel] [XEN PATCH v3 00/23] xen: Build system improvements Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 01/23] xen/include: remove include of Config.mk Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 02/23] Makefile: Fix install-tests Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 03/23] xen/build: Remove confusing comment on the %.s:%.S rule Anthony PERARD
2020-02-26 11:53   ` Wei Liu
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 04/23] xen/build: remove use of AFLAGS-y Anthony PERARD
2020-02-26 12:58   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 05/23] xen/build: Allow to test clang .include without asm symlink Anthony PERARD
2020-02-27  9:05   ` Roger Pau Monné
2020-02-27  9:22     ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 06/23] xen/build: Fix section-renaming of libfdt and libelf Anthony PERARD
2020-02-27  9:38   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 07/23] xen/build: Use obj-y += subdir/ instead of subdir-y Anthony PERARD
2020-02-27  9:22   ` Roger Pau Monné
2020-02-27  9:43   ` Jan Beulich
2020-03-04 14:14     ` Jan Beulich
2020-03-05  9:24   ` Jan Beulich
2020-03-05 13:42     ` Andrew Cooper
2020-03-05 15:02     ` Julien Grall
2020-03-05 15:59       ` Anthony PERARD
2020-03-05 16:31         ` Julien Grall
2020-03-09  6:46     ` Tian, Kevin
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 08/23] xen/build: use $(clean) shorthand for clean targets Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 09/23] xen/build: extract clean target from Rules.mk Anthony PERARD
2020-03-04 14:13   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 10/23] xen/build: run targets csopes, tags, .. without Rules.mk Anthony PERARD
2020-03-04 14:17   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 11/23] xen/build: make tests in test/ directly Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 12/23] xen/build: Move as-option-add to xen/ Anthony PERARD
2020-03-04 14:17   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 13/23] xen/build: include include/config/auto.conf in main Makefile Anthony PERARD
2020-03-04 14:29   ` Jan Beulich
2020-03-10 17:10     ` Anthony PERARD
2020-03-11  9:26       ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 14/23] xen/build: use new $(c_flags) and $(a_flags) instead of $(CFLAGS) Anthony PERARD
2020-02-27 10:22   ` Roger Pau Monné
2020-03-10 17:55     ` Anthony PERARD
2020-03-04 14:42   ` Jan Beulich
2020-03-10 17:43     ` Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 15/23] xen/build: have the root Makefile generates the CFLAGS Anthony PERARD
2020-02-27 11:05   ` Roger Pau Monné
2020-03-17 18:05     ` Anthony PERARD
2020-03-19 16:24       ` Anthony PERARD
2020-03-23 15:11         ` Roger Pau Monné
2020-03-24 17:11           ` [Xen-devel] " Anthony PERARD
2020-03-04 15:00   ` Jan Beulich
2020-03-17 18:35     ` Anthony PERARD
2020-03-18 10:20       ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 16/23] xen/build: introduce if_changed and if_changed_rule Anthony PERARD
2020-03-04 15:45   ` Jan Beulich
2020-03-18 10:44     ` Anthony PERARD
2020-03-18 11:14       ` Jan Beulich [this message]
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 17/23] xen/build: Start using if_changed Anthony PERARD
2020-02-27 13:09   ` Roger Pau Monné
2020-03-04 16:00     ` Jan Beulich
2020-03-18 10:52       ` Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 18/23] xen/build: use if_changed on built_in.o Anthony PERARD
2020-03-04 16:03   ` Jan Beulich
2020-03-18 10:55     ` Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 19/23] xen/build: Use if_changed_rules with %.o:%.c targets Anthony PERARD
2020-03-04 16:09   ` Jan Beulich
2020-03-18 11:14     ` Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 20/23] xen/build: factorise generation of the linker scripts Anthony PERARD
2020-02-27 13:14   ` Roger Pau Monné
2020-03-05 11:07     ` Jan Beulich
2020-03-05 11:05   ` Jan Beulich
2020-03-18 11:59     ` Anthony PERARD
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 21/23] xen/build: Use if_changed for prelink*.o Anthony PERARD
2020-02-27 13:16   ` Roger Pau Monné
2020-03-04 16:12     ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 22/23] xen, symbols: rework file symbols selection Anthony PERARD
2020-03-05 14:44   ` Jan Beulich
2020-02-26 11:33 ` [Xen-devel] [XEN PATCH v3 23/23] xen/build: use if_changed to build guest_%.o Anthony PERARD
2020-03-05 15:12   ` Jan Beulich
2020-02-27 21:17 ` [Xen-devel] [XEN PATCH v3 00/23] xen: Build system improvements Stewart Hildebrand
2020-03-06 10:12   ` Anthony PERARD

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