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Date:   Thu, 1 Jul 2021 18:23:52 -0400
From:   Jeff King <peff@peff.net>
To:     =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason <avarab@gmail.com>
Cc:     git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
        Denton Liu <liu.denton@gmail.com>,
        Felipe Contreras <felipe.contreras@gmail.com>,
        Kristof Provost <Kristof@provost-engineering.be>,
        Taylor Blau <me@ttaylorr.com>
Subject: Re: [PATCH v2 3/5] Makefile: fix "cscope" target to refer to
 cscope.out
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References: <cover-0.3-00000000000-20210622T141844Z-avarab@gmail.com>
 <cover-0.5-0000000000-20210629T110837Z-avarab@gmail.com>
 <patch-3.5-35c8b83904-20210629T110837Z-avarab@gmail.com>
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On Tue, Jun 29, 2021 at 01:12:57PM +0200, Ævar Arnfjörð Bjarmason wrote:

> diff --git a/Makefile b/Makefile
> index faa8900097..2e3b257164 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -2737,10 +2737,12 @@ tags: FORCE
>  	$(FIND_SOURCE_FILES) | xargs ctags -a -o tags+ && \
>  	mv tags+ tags
>  
> +cscope.out:
> +	$(QUIET_GEN)$(RM) cscope.out && \
> +	$(FIND_SOURCE_FILES) | xargs cscope -f$@ -b
> +
>  .PHONY: cscope
> -cscope:
> -	$(QUIET_GEN)$(RM) cscope* && \
> -	$(FIND_SOURCE_FILES) | xargs cscope -b
> +cscope: cscope.out

Doesn't this break subsequent runs after the first generation? With a
phony "cscope" target, "make cscope" will always run the command, even
if it's not necessary. But with a real "cscope.out" target but not
dependencies, it will _never_ run it, even if one of the files changed.

E.g., with your patch:

  $ make cscope.out
    GEN cscope.out

  $ make cscope.out
  make: 'cscope.out' is up to date.

  $ echo 'void foo(void) { }' >>git.c
  $ make cscope.out
  GIT_VERSION = 2.32.0.96.g5daee1b7bb.dirty
  make: 'cscope.out' is up to date.

-Peff