Re: [PATCH 04/17] Makefile: a dry-run can error out if no perl. Document the issue

From: Junio C Hamano <gitster@pobox.com>
To: Philip Oakley <philipoakley@iee.org>
Cc: GitList <git@vger.kernel.org>,  MsysGitList <msysgit@googlegroups.com>
Subject: Re: [PATCH 04/17] Makefile: a dry-run can error out if no perl. Document the issue
Date: Thu, 25 Jun 2015 08:24:31 -0700	[thread overview]
Message-ID: <xmqq8ub724ls.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <1435190633-2208-5-git-send-email-philipoakley@iee.org> (Philip Oakley's message of "Thu, 25 Jun 2015 01:03:40 +0100")

Philip Oakley <philipoakley@iee.org> writes:

> A 'make -n' dry-run is used as part of the /compat/vcbuild and
> /contrib/buildsystems code. The commit ee9be06 (perl: detect new files
> in MakeMaker builds, 2012-07-27) was not aware of that dry-run usage
> and thus would not execute the target.
>
> Add a comment to the make file stating the issue and the available
> solutions of either NO_PERL or a '+recipe'.

I am not sure what this patch is trying to achieve.

If you are not touching what this Makefile actually does, then I
would imagine that you are running the "buildsystems code" that
actually drives 'make -n' with some "available solution" (perhaps
you are running 'make -n NO_PERL=NoThanks' or something like that)?
Then instead of a command like this that nobody would read in this
file, the same command can instead go there to explain what the
"workaround" (e.g. unusual-looking 'make -n NO_PERL=NoThanks') is
doing?

I suspect you mean by +recipe that you modify this makefile to make
such a workaround unnecessary?  If that is the case, why isn't such
a change actually be done with this commit, instead of a comment?

I am not sure what this patch is trying to achieve.

Puzzled...

>
> Signed-off-by: Philip Oakley <philipoakley@iee.org>
> ---
>  Makefile | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 149f1c7..22108bb 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1746,6 +1746,9 @@ $(SCRIPT_PERL_GEN): perl/perl.mak
>  
>  perl/perl.mak: perl/PM.stamp
>  
> +# 'make -n' (dry-run) will not execute this target which creates/updates the PM.stamp file.
> +# To avoid the error of failing to find the target PM.stamp, either use NO_PERL=1 (YesPlease),
> +# or add a leading '+' to the recipe '+$(QUIET_GEN)$(FIND) perl ...' so that it is executed.
>  perl/PM.stamp: FORCE
>  	@$(FIND) perl -type f -name '*.pm' | sort >$@+ && \
>  	{ cmp $@+ $@ >/dev/null 2>/dev/null || mv $@+ $@; } && \
> -- 
> 2.3.1
>
> -- 

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