Re: [boost] Boost CMake support - Request for Comment

Subject: Re: [boost] Boost CMake support - Request for Comment
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2018-10-09 23:58:11

On Wed, Oct 10, 2018 at 2:43 AM Edward Diener via Boost
<boost_at_[hidden]> wrote:
>
> The feature is essentially programmed by config and predef to provide
> build-time testing of compiler support and testing of such things like
> the OS versions and compiler versions etc. See
> https://www.boost.org/doc/libs/1_68_0/libs/config/doc/html/boost_config/build_config.html
> for the explanation in config and
> https://www.boost.org/doc/libs/1_68_0/doc/html/predef/check_utilities.html
> for checking predef values at build time. The basics of the feature are
> offered by Boost Build as explained at
> https://boostorg.github.io/build/manual/develop/index.html#bbv2.reference.rules
> in reference to the check-target-builds rule. Plenty of libraries use
> the feature during testing and I imagine that some of them may use the
> feature during building. Asking individual libraries to convert their
> tests or build to use some CMake equivalent, for every possible setting
> in config and predef which they use, is not realistic. I understand that
> CMake may have an equivalent technique, but who is going to program that
> technique to offer all the equivalents which config and predef currently
> offer ?

Why do you think a potential Boost.CMake proposal cannot offer an
equivalent of check-target-builds that internally uses the checks
based on Boost.Config or Boost.Predef? Because, AFAIU,
check-target-builds is exactly that - a compile test that involves a
preprocessor check of one of the macros + a bit of caching on
Boost.Build side. Doesn't sound like something that can't be done in
CMake.

As for the conversion process, I don't think it is reasonable to
expect a single person, a Boost.CMake candidate author, to convert all
Boost Jamfiles to CMake. Library authors *will* have to learn the new
build system and do the conversion of their libraries. Hopefully, a
proposed Boost.CMake should make it easier, but it won't be a free
ride.

PS: Also, let's not over-quote, please.