Re: [PATCH] Makefile: add and use the ".DELETE_ON_ERROR" flag

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 29, 2021, 21:38 UTC
Message-ID: <xmqqv95wuza3.fsf@gitster.g>
In-Reply-To: <875yxxgkav.fsf@evledraar.gmail.com>

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

> Even if you don't care about the end result or making git easier to hack
> on for people who don't share your setup, I'd think that making those
> rules consistent across the board makes things less complex, not more.

I think that it is where we disagree. "Remove $@+ and $@, generate into $@+ and then move it to $@" idiom has a legitimate reason to be used, and I do not want to see it blindly used where there is no reason to do so. It misleads less experienced readers.

If we write a custom script that does not promise atomicity, it is a quite natural pattern to use, and it is clear to readers what is going on, especially when "generate into $@+" step is done via redirection. I despise "$(CC) -o $@+ && mv $@+ $@" because there simply shouldn't be a need to do so---unlike our custom script that sends its output to its standard output, $(CC) ought to know better.

But as you said elsewhere, the patch in question is *not* about adding more use of "mv $@+ $@" in inappropriate contexts, so let's stop discussing it now. We take advantage of .DELETE_ON_ERROR that allows us to use the upfront "rm -f $@ $@+" we do in the idiom, which is a good thing.