Re: [boost] [cmake] Pull request announcement

Subject: Re: [boost] [cmake] Pull request announcement
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2018-09-27 08:29:00

On Thu, 27 Sep 2018 at 05:18, Peter Dimov via Boost
<boost_at_[hidden]> wrote:
> Stefan Seefeld wrote:
>
> > Indeed: While the above is a great starting point to support what I want,
> > I don't want to loose the ability for BPL to be built (and tested) as part
> > of the rest of Boost. I would thus prefer something that gives me the
> > ability to choose the build strategy e.g. using some command-line option,
> > including flag to be passed to the build (e.g., `b2 ... standalone=on`),
> > rather than having to modify the (build) code.
>
> Scanning for Jamroot to identify the project root is fundamental to Jam (the
> Perforce one). We could perhaps add something like
>
>     b2 --jamroot=.
>
> that would act as if there were an empty Jamroot at . (or equivalently if
> the Jamfile at . were named Jamroot.)

Does it mean there could be two jamfile-s?
libs/gil/Jamroot for standalone build
libs/gil/Jamfile for in-Boost tree build
and the latter is simply ignored in normal b2 run, ie. without  --jamroot=.

I think, this would be also very helpful to apply the Jamroot trick [1],
recently presented to me by Steven Watanabe,
to significantly speed up b2 startup procedures:

"""
Try inserting a Jamroot to block the extra work that Boost's
Jamroot is doing automatically. This is a bad idea in
general, as the aforementioned work is important, but it
should be okay as long as you set up `b2 headers` beforehand
and do not use any separately compiled boost libraries.
"""

[1] https://lists.boost.org/boost-build/2018/08/29977.php

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net