Re: [Boost-build] [boost] [build] [config] check_target_builds and feature.subfeature composition

Subject: Re: [Boost-build] [boost] [build] [config] check_target_builds and feature.subfeature composition
From: Stefan Seefeld (stefan_at_[hidden])
Date: 2017-01-24 09:13:31

On 24.01.2017 03:30, John Maddock wrote:
>
>>> Yes I have, I brought it up, nothing happened. I stopped using
>>> check_target_builds.
>>>
>>    The problem is that check_target_builds tries to
>> guess which features are important, and does it
>> badly (via a hard-coded list).
>
> IMO this is just plain wrong - any command line change could change
> the behaviour of the compile - I would rather loose the caching (which
> itself is problematic at times) that have it yield the wrong answer.

Allow me to tie this back to an earlier conversation:

It seems this issue arises because b2 allows multiple build variants to
be built at once, so (at least theoretically) each would need to run its
own set of config checks.
I understand that there are features that may take on different values
within a single build, but to open that door widely and let multiple
feature values be set at build time just makes the whole process so much
more complex. Wouldn't there be a way to simplify this to get the
complexity in check ?
Alternatively, config checks need to become (intermediate) build targets
by themselves, and "caching" would need to be handled the same as for
any other target (such as object files).

Regards,
        Stefan

-- 
      ...ich hab' noch einen Koffer in Berlin...