Re: [boost] find_package(Boost) support

Subject: Re: [boost] find_package(Boost) support
From: Roger Leigh (rleigh_at_[hidden])
Date: 2019-02-01 11:58:32

On 12/01/2019 18:33, Peter Dimov via Boost wrote:
> The current master and develop branches now install the necessary 
> BoostConfig.cmake file (in $prefix/lib/cmake) such that f.ex. the CMake 
> command
> 
>  Â Â  find_package(Boost REQUIRED filesystem)
> 
> will find Boost 1.70 using the config file, rather than via 
> FindBoost.cmake (*) (if the Boost installation prefix is in CMake's 
> prefix search path.)

A heads up from the CMake side.  Unfortunately, this is causing breakage 
with FindBoost, and we got the first bug:

   https://gitlab.kitware.com/cmake/cmake/issues/18865

It looks like for the specific modules concerned, it's not behaving 
entirely compatibly with FindBoost.  Would it be possible to rectify 
this?  Since FindBoost is delegating to these new Config modules when 
present, it's a requirement that it behave identically to avoid any 
breakage.

Alternatively, we could remove the delegation logic in FindBoost and do 
a hard break, so users will have to explicitly opt in to the 
Boost-provided Config files.  It wouldn't be as nice, but it might be 
more robust; and it would also obviate the need for strict 
compatibility.  I'd prefer this to be an option of last resort though.

The main point I wanted to make is that while the transition might have 
some disruptions, we can't have an incomplete or broken state for 1.70, 
or major chaos will ensue.

Kind regards,
Roger