[Buildroot] [PATCH v3 1/3] package/waf: add a blind Config.in.host

[Carlos Santos <casantos@datacom.com.br>]

> From: "Yann Morin" <yann.morin.1998@free.fr>
> To: "Thomas Petazzoni" <thomas.petazzoni@bootlin.com>
> Cc: "Peter Korsgaard" <peter@korsgaard.com>, "Mahyar Koshkouei" <mahyar.koshkouei@gmail.com>, "Thomas De Schampheleire"
> <thomas.de_schampheleire@nokia.com>, "buildroot" <buildroot@buildroot.org>
> Sent: Quinta-feira, 3 de janeiro de 2019 20:06:52
> Subject: Re: [Buildroot] [PATCH v3 1/3] package/waf: add a blind Config.in.host

> Thomas, All,
> 
> On 2019-01-03 22:50 +0100, Thomas Petazzoni spake thusly:
>> On Wed, 26 Dec 2018 22:55:21 +0100, Yann E. MORIN wrote:
>> > Well, I am not really happy with that, though: do we really plan on
>> > having packages really select all the host tools they need?
>> > 
>> > If so, do we really envision autotools-based packages selecting
>> > host-autoconf, host-automake, host-libtool? And then packages that use
>> > host-pkgconf you should also select it...
>> > 
>> > Also, what about host-cmake, which is conditionally built, but for which
>> > we do not have the info in kconfig? (well, we can argue we'd have to do
>> > like we do for host-gcc, but still). Oh, and host-tar, host-flex,
>> > host-bison, and so on... :-/
>> 
>> Meh, I hadn't thought of conditional packages like host-tar, host-cmake
>> and so on.
>> 
>> > So, no, I'm not happy with that direction...
>> > 
>> >     config BR2_PACKAGE_FOO
>> >         bool "foo"
>> >         select BR2_PACKAGE_HOST_AUTOCONF
>> >         select BR2_PACKAGE_HOST_AUTOMAKE
>> >         select BR2_PACKAGE_HOST_LIBTOOL
>> >         select BR2_PACKAGE_MAYBE_HOST_TAR
>> >         select BR2_PACKAGE_MAYBE_HOST_FLEX_FOR_KCONFIG
>> >         select BR2_PACKAGE_MAYBE_HOST_BISON_FOR_KCONFIG
>> >         select BR2_PACKAGE_HOST_PKGCONF
>> > 
>> > Unles we're planning on hiding that away into meta-config, like:
>> > 
>> >     config BR2_PACKAGE_FOO
>> >         bool "foo"
>> >         select BR2_AUTOTOOLS_PACKAGE # mimick $(eval $(autotools-package))
>> >         select BR2_PACKAGE_HOST_PKGCONF_BECAUSE_IT_S_NOT_MANDATORY
>> > 
>> > And still, the optionally-required host packages like tar, flex et al.
>> > are not covered...
>> > 
>> > Meh... :-(
>> 
>> Indeed, I understand the "Meh" here. I hadn't really realized what it
>> would mean to have Config.in.host options for all packages, and
>> properly selected by all its users.
> 
> To be fait, I was initially also in favour of adding Config.in.host
> options for all host packages. But this waf patch made me change my
> mind, becasue of the above...
> 
>> But still, there are a number of cases where it would really help, so
>> that a given host package can be aware that another host package has
>> been built with a given feature (or not). Or precisely to force that a
>> certain host package is built with a given option. For example, in
>> host-python, we had situations where only a given package needed
>> host-python to be built with FOO support, and since we don't have any
>> BR2_PACKAGE_HOST_PYTHON_FOO option, our only choice was to
>> unconditionally enable FOO support in host-python, adding build time to
>> everyone, even if FOO in host-python might only be needed for one
>> obscure package.
> 
> In this case, maybe we could simply depart from the rule, and just have
> python/Config.in.host contain just:
> 
>    # Select this if you need host-python to support 'stuff'
>    config BR2_NEEDS_HOST_PYTHON_WITH_STUFF
>        bool
> 
> And then, python/python.mk would have:
> 
>    ifeq ($(BR2_NEEDS_HOST_PYTHON_WITH_STUFF),y)
>    HOST_PYTHON_CONF_OPTS += --with-stuff
>    else
>    HOST_PYTHON_CONF_OPTS += --without-stuff
>    endif
> 
> Regards,
> Yann E. MORIN.
> 
>> It seems like we don't have a very conclusive decision on this topic at
>> this point.

Well, I'm happy that my work helped you guys to analyze the pros and
cons of having Config.in.host for all host packages. Looks like it's
not a good idea, so I will mark the patches as refused in patchwork.

-- 
Carlos Santos (Casantos) - DATACOM, P&D