Re: [boost] Did Boost 1.59.0 change the meaning of "using python : 3.4 : ..." in user-config.jam?

Subject: Re: [boost] Did Boost 1.59.0 change the meaning of "using python : 3.4 : ..." in user-config.jam?
From: Vladimir Prus (vladimir.prus_at_[hidden])
Date: 2015-08-23 13:05:59

On 21-Aug-15 8:11 PM, Jonathan Wakely wrote:
> Hi,
>
> I'm trying to update the Fedora rawhide package to Boost 1.59.0 and
> the build fails with the output below (ignore the MPI warnings).
>
> We build with the following in user-config.jam:
>
> # This _adds_ extra python version.  It doesn't replace whatever
> # python 2.X is default on the system.
> using python : 3.4 : /usr/bin/python3 : /usr/include/python3.4m : : : : m ;
>
>
> Is that comment no longer true?

Jonathan,

I've just tried with the following user-config.jam:

        using python : 2.7 : C:/Python27 ;
        using python : 3.4 : C:/Python34 ;

and was able to do both "b2 python=2.7" and "b2 python=3.4" and these appear to pick different
python version - at least the latter produces a different set of warnings.

I'm not entirely sure what the comment mean regarding system python 2.X. There is code in
libs/python/build/Jamfile.v2 that does "using python" if no previous python initialization
is found. That code is executed after user-config.jam and all other config files. I don't
believe there was ever code to add 2.X python implicitly, so if you have "using python : 3.4",
you must have "using python : 2.7" somewhere too for that version to be used.

Maybe 2.7 used to be initialized in site-config.jam?

Does that help?

- Volodya