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

["Philip Oakley" <philipoakley@iee.org>]

From: "Junio C Hamano" <gitster@pobox.com>
> 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.

It was probably a bit of 'don't mess with working code', given that I'd 
used the NO_PERL solution, rather 'document the issue'. The issue had me 
stuck for a while. The possible use of '+' came later when driving down 
through the Makefile manual.

>
> 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?

Yes.  See above about the lack of 'fearless coding'; been working in 
real world engineering too long ;-)

>
> 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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