[Boost-build] Python build fails with 1.64.RC1 on Windows

Subject: [Boost-build] Python build fails with 1.64.RC1 on Windows
From: Sophonet (boost_at_[hidden])
Date: 2017-03-28 11:38:53

Hi list,

a few months ago, I have reported a bug in boost build which was 
introduced between 1.61 and 1.62 and screwed up python building when 
using user-config.jam - specific python versions (order of python 
versions was not recognized anymore, and only the first python 
configuration in user-config.jam was picked for building). See here: 
https://svn.boost.org/trac/boost/ticket/12515

In boost 1.63, probably to a related issue, an additional problem 
occurred even when the correct python version was the first entry in 
user-config.jam. In that case, the installation could not find the 
boost3 numpy library when installing (which indeed did not exist). I 
have heard from other people that building boost 1.63 with numpy would 
work if user-config.jam does not exist (which I have not checked 
though)...

After 1.63 release, I have noticed some changes in the boost-python 
specific build chain (related to 
https://github.com/boostorg/build/issues/163). However, when trying 
1.64.RC1, boost python does actually not build at all anymore (I am 
using python 3.6), even if user-config.jam is deleted and even if 
explicitly saying --with-python.

There are two things.

1. When building b2, an error message appears:

'powershell' is not recognized as an internal or external command,
operable program or batch file.

...but building continues

2.

   a) user-config.jam is not present: There is no activity at all to 
build boost python, and even installation just stays silent and does 
nothing without any error message.

   b) user-config.jam is present, and even if the first python entry 
matches the correct version (3.6 in my case), nothing happens, but a few 
more lines appear on the screen:

     - hardlinks supported      : yes (cached)
error: No best alternative for libs/python/build/boost_python3
     next alternative: required properties: <python>3.6
         matched
     next alternative: required properties: <python>3.6
         matched
...found 1 target...
...updating 1 target...
config-cache.write 
D:\SW\build\quinta_rel_msvc14\boost_1_64_0\boost\bin.v2\project-cache.jam

I hope that it would be easy to fix these problems before the final 1.64 
release - since the first problems occured, as mentioned above, already 
in 1.62, which is more than half a year ago.

If there are any hints where I can help, please post to this list - 
unfortunately, I am not that experienced in boost build's jam.

Thanks a lot,

      Sophonet