Re: [Buildroot] [PATCH 1/1] package/pkg-generic.mk: fix rule order for re{install, build, configure}

["Yann E. MORIN" <yann.morin.1998@free.fr>]

James, All,

Thanks again for working on such grunt work, it's much appreaciated!

On 2022-10-17 21:46 -0600, James Hilliard spake thusly:
> These command rely on the clean operations being first so that the
> stamp files being deleted will rebuild the targets.
> 
> The execution ordering of the clean and rebuild operations may
> change, for example if --shuffle=reversed is set.
> 
> To ensure the evaluation order is always correct use double colon
> rules to make the evaluation order explicit as per make docs:
> 
> The double-colon rules for a target are executed in the order they
> appear in the makefile.

I am not convinced that we should switch over to using double-colons.

As I reviewed your other related patch about legal-info [0], the make
manual [1] suggests that double-colons are rally intended for cases
where "the method used to update a target differs depending on which
prerequisite files caused the update" and "double-colon rules really
make sense are those where the order of executing the recipes would not
matter".

So, we'd use a mechanism where order should not matter, to solve an
issue with ordering. That'd be weird...

Yes, the manual states that "double-colon rules for a target are
executed in the order they appear in the makefile", but that really
looks like a side-effect of another goal.

Also, we'd need to carefully review all our Makefile to ensure that
there are no other cases wehre ordering of prerequisites matter. We'd
also have to be careful every time we introduce a new rule and remember
to check whether it depends on the ordering prereauisites or not, adn
worse yet, also whether we can afford the rule to be parallel-safe or
not (see the explanation for that in the legal-info review).

Having colons and double-colons is going to be quite a headache... We
already have issues with remembering that we need to use $$ to expand
variables in some places, and the rules there are relatively clean and
explicit, but for the :: case, I'm afraid that's going to be a bit more
complex.

We currently have a single location where we use double-colon:
    support/kconfig/Makefile.br

which is added by our patch against kconfig:
    support/kconfig/patches/10-br-build-system.patch

which dates back to 2010:
    7c524dd0b683 Clean up our patches against kconfig

which got in three in 2007:
    a665ed34960b - pull kconfig from linux-2.6.21.5

So, I'd like that we get another way to fix that, if possible...

Again, thanks a lot for spending efforts in that area, this is really
great!

[0] https://lore.kernel.org/buildroot/20230212091914.GJ2796@scaer/
[1] https://www.gnu.org/software/make/manual/make.html#Double_002dColon

Regards,
Yann E. MORIN.

> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
> ---
>  package/pkg-generic.mk | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
> index f24e03a325..6cb461af90 100644
> --- a/package/pkg-generic.mk
> +++ b/package/pkg-generic.mk
> @@ -1057,17 +1057,20 @@ endif
>  			rm -f $$($(2)_TARGET_INSTALL_IMAGES)
>  			rm -f $$($(2)_TARGET_INSTALL_HOST)
>  
> -$(1)-reinstall:		$(1)-clean-for-reinstall $(1)
> +$(1)-reinstall::		$(1)-clean-for-reinstall
> +$(1)-reinstall::		$(1)
>  
>  $(1)-clean-for-rebuild: $(1)-clean-for-reinstall
>  			rm -f $$($(2)_TARGET_BUILD)
>  
> -$(1)-rebuild:		$(1)-clean-for-rebuild $(1)
> +$(1)-rebuild::		$(1)-clean-for-rebuild
> +$(1)-rebuild::		$(1)
>  
>  $(1)-clean-for-reconfigure: $(1)-clean-for-rebuild
>  			rm -f $$($(2)_TARGET_CONFIGURE)
>  
> -$(1)-reconfigure:	$(1)-clean-for-reconfigure $(1)
> +$(1)-reconfigure::	$(1)-clean-for-reconfigure
> +$(1)-reconfigure::	$(1)
>  
>  # define the PKG variable for all targets, containing the
>  # uppercase package variable prefix
> -- 
> 2.34.1
> 
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