Re: [PATCH] Makefile: dedup git-ls-files output to prevent duplicate targets

From: Junio C Hamano <gitster@pobox.com>
To: Jiang Xin <worldhello.net@gmail.com>
Cc: "Git List" <git@vger.kernel.org>,
	"Jiang Xin" <zhiyou.jx@alibaba-inc.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Alexander Shopov" <ash@kambanaria.org>,
	"Jordi Mas" <jmas@softcatala.org>,
	"Matthias Rüster" <matthias.ruester@gmail.com>,
	"Jimmy Angelakos" <vyruss@hellug.gr>,
	"Christopher Díaz" <christopher.diaz.riv@gmail.com>,
	"Jean-Noël Avila" <jn.avila@free.fr>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Alessandro Menti" <alessandro.menti@alessandromenti.it>,
	"Gwan-gyeong Mun" <elongbug@gmail.com>, Arusekk <arek_koz@o2.pl>,
	"Daniel Santos" <dacs.git@brilhante.top>,
	"Dimitriy Ryazantcev" <DJm00n@mail.ru>,
	"Peter Krefting" <peter@softwolves.pp.se>,
	"Emir SARI" <bitigchi@me.com>,
	"Trần Ngọc Quân" <vnwildman@gmail.com>,
	"Fangyi Zhou" <me@fangyi.io>, "Yi-Jyun Pan" <pan93412@gmail.com>
Subject: Re: [PATCH] Makefile: dedup git-ls-files output to prevent duplicate targets
Date: Wed, 25 May 2022 23:23:25 -0700	[thread overview]
Message-ID: <xmqq5yls3j8i.fsf@gitster.g> (raw)
In-Reply-To: <CANYiYbEcNJ7+7XW-8-v+p8q=aiOP9RJYvST8ethVjxVdNugR5Q@mail.gmail.com> (Jiang Xin's message of "Thu, 26 May 2022 14:06:54 +0800")

Jiang Xin <worldhello.net@gmail.com> writes:

>>         )
>> -FOUND_SOURCE_FILES := $(shell $(SOURCES_CMD))
>> +FOUND_SOURCE_FILES := $(sort $(shell $(SOURCES_CMD)))
>>
>>  FOUND_C_SOURCES = $(filter %.c,$(FOUND_SOURCE_FILES))
>>  FOUND_H_SOURCES = $(filter %.h,$(FOUND_SOURCE_FILES))
>>
>
> If I disabled the git-ls-files command like below,
>
>     @@ -846,7 +846,7 @@ generated-hdrs: $(GENERATED_H)
>...
> This is because the three generated header files (defined in
> $(GENERATED_H)) are also included in the result of "SOURCES_CMD". We
> can fix this by sorting LOCALIZED_C:
>
>     -LOCALIZED_C = $(FOUND_C_SOURCES) $(FOUND_H_SOURCES) $(SCALAR_SOURCES) \
>     -             $(GENERATED_H)
>     +LOCALIZED_C = $(sort $(FOUND_C_SOURCES) $(FOUND_H_SOURCES)
> $(SCALAR_SOURCES) \
>     +               $(GENERATED_H))

If you make FOUND_SOURCE_FILES unique upfront, the at least there
wouldn't be any duplicates there.  Do you mean that some of what is
in FOUND_SOURCE_FILES appear in either SCALAR_SOURCES or GENERATED_H?

If not, I think deduplicating near the source of the issue, i.e.

  FOUND_SOURCE_FILES := $(sort $(shell $(SOURCES_CMD)))

may be sufficient.  Deduplicating near the consumer, like
LOCALIZED_C, may force us to dedup all the consumers of it (e.g.
LOCALIZED_C is not the sole consumer of FOUND_C_SOURCES; you'd need
to sort the input to COCCI_SOURCES, for example).

Thanks.