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From: Junio C Hamano <gitster@pobox.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH] Makefile: generate 'git' as 'cc [...] -o git+ && mv git+ git'
Date: Mon, 08 Mar 2021 09:21:07 -0800	[thread overview]
Message-ID: <xmqqpn097e9o.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <87ft15kegn.fsf@evledraar.gmail.com> ("Ævar Arnfjörð Bjarmason"'s message of "Mon, 08 Mar 2021 13:38:32 +0100")

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> We have a lot of existing rules in the Makefile that are of the form:
>
>     make thing >thing+ &&
>     mv thing+ thing
>
> Where we're not doing the rename dance to avoid clobbering the file
> we're reading.

I am afraid that you are totally misreading the intent of that age
old convention, which is spelled:

	thing:
		rm -f thing thing+
		prepare contents for thing >thing+
		mv thing+ thing

It protects us from a failure mode where "prepare contents for
thing" step is broken and leaves a "thing" that does not work, but
confuses make that make does not need to rebuild it, if you wrote it
as such:

	thing:
		prepare contents for thing >thing

I think more recent make actually has some knob you can tweak to
tell "if the rule failed, remove it", but the convention predates
it.

In any case, it is not "we are trying to make thing available while
it is being rewritten" at all.

  reply	other threads:[~2021-03-08 17:21 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-07 13:20 [PATCH] Makefile: generate 'git' as 'cc [...] -o git+ && mv git+ git' Ævar Arnfjörð Bjarmason
2021-03-07 20:41 ` Junio C Hamano
2021-03-08 12:38   ` Ævar Arnfjörð Bjarmason
2021-03-08 17:21     ` Junio C Hamano [this message]
2021-03-08 18:26     ` Jeff King
2021-03-29 16:20 ` [PATCH v2 0/5] Makefile: don't die on AIX with open ./git Ævar Arnfjörð Bjarmason
2021-03-29 16:20   ` [PATCH v2 1/5] Makefile: rename objects in-place, don't clobber Ævar Arnfjörð Bjarmason
2021-03-29 18:21     ` Junio C Hamano
2021-03-29 18:26       ` Junio C Hamano
2021-03-29 23:24       ` Ævar Arnfjörð Bjarmason
2021-03-30  0:21         ` Junio C Hamano
2021-03-31 14:17           ` Ævar Arnfjörð Bjarmason
2021-03-31 18:50             ` Junio C Hamano
2021-03-29 16:20   ` [PATCH v2 2/5] Makefile: rename scripts " Ævar Arnfjörð Bjarmason
2021-03-29 18:40     ` Junio C Hamano
2021-03-29 23:28       ` Ævar Arnfjörð Bjarmason
2021-03-29 16:20   ` [PATCH v2 3/5] Makefile: don't needlessly "rm $@ $@+" before "mv $@+ $@" Ævar Arnfjörð Bjarmason
2021-03-29 18:46     ` Junio C Hamano
2021-03-29 16:20   ` [PATCH v2 4/5] Makefile: add the ".DELETE_ON_ERROR" flag Ævar Arnfjörð Bjarmason
2021-03-29 18:51     ` Junio C Hamano
2021-03-29 23:31       ` Ævar Arnfjörð Bjarmason
2021-03-29 23:58         ` Junio C Hamano
2021-03-30 15:11         ` Jeff King
2021-03-30 18:36           ` Junio C Hamano
2021-03-31  6:58             ` Jeff King
2021-03-31 18:36               ` Junio C Hamano
2021-03-31 22:29                 ` Johannes Schindelin
2021-03-29 16:20   ` [PATCH v2 5/5] Makefile: don't "rm configure" before generating it Ævar Arnfjörð Bjarmason
2021-03-29 16:31   ` [PATCH 0/6] Makefile: make non-symlink & non-hardlink install sane Ævar Arnfjörð Bjarmason
2021-03-29 16:31     ` [PATCH 1/6] Makefile: symlink the same way under "symlinks" and "no hardlinks" Ævar Arnfjörð Bjarmason
2021-03-29 22:17       ` Junio C Hamano
2021-03-29 16:31     ` [PATCH 2/6] Makefile: begin refactoring out "ln || ln -s || cp" pattern Ævar Arnfjörð Bjarmason
2021-03-29 22:20       ` Junio C Hamano
2021-03-29 16:31     ` [PATCH 3/6] Makefile: refactor " Ævar Arnfjörð Bjarmason
2021-03-29 22:24       ` Junio C Hamano
2021-03-30 15:20         ` Jeff King
2021-03-30 18:36           ` Junio C Hamano
2021-03-29 16:31     ` [PATCH 4/6] Makefile: make INSTALL_SYMLINKS affect the build directory Ævar Arnfjörð Bjarmason
2021-03-29 22:31       ` Junio C Hamano
2021-03-31 14:04         ` Ævar Arnfjörð Bjarmason
2021-03-29 16:31     ` [PATCH 5/6] Makefile: use "ln -f" instead of "rm && ln" Ævar Arnfjörð Bjarmason
2021-03-29 22:46       ` Junio C Hamano
2021-03-29 16:31     ` [PATCH 6/6] Makefile: add a INSTALL_FALLBACK_LN_CP mode Ævar Arnfjörð Bjarmason
2021-03-29 22:53       ` Junio C Hamano
2021-03-31 14:03         ` Ævar Arnfjörð Bjarmason
2021-03-31 18:45           ` Junio C Hamano
2021-03-31 19:01             ` Ævar Arnfjörð Bjarmason
2021-03-29 23:08     ` [PATCH 0/6] Makefile: make non-symlink & non-hardlink install sane Junio C Hamano

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