python.jam: init's condition parameter, extra-libs-conditional

Vladimir Prus <ghostcs.msu.su> writes:

> On Friday 29 September 2006 19:54, David Abrahams
wrote:
>> What the heck is this condition parameter supposed
to do?  
>
> There's no such parameter. 

  rule init-unix ( version ? : root ? : includes ? :
libraries ? : condition * )
                                                            
      ^^^^^^^^^

> Do you mean 'extra-lib-conditional' variable in 
> init-unix? 

That too.

> If yes, commented as attached.
>
>> There's no documentation at all, and the name
really gives me no
>> clue as to what it's for.  It appears to be
gcc-specific?
>
> If you mean the 'condition' parameter to init-unix, 

Yes, that.

> this is meant to allow one 
> to specify specific condition under which the
configured version of Python 
> will be used. So that you can configure two python
versions which will be 
> used for different build properties, just like
alternatives mechanism allow. 
> I don't remember exactly why it was added, either
building 32 and 64-bit 
> tests, or something like that.

Or for building with cygwin gcc and vc++ from an NT
command-line.
Nice.  But it needs to be commented.

>> The same sort of bafflement goes for
cygwin-condition
>
> Originally meant so that you can configure Python
differently for cygwin and 
> native windows compilers. Essentially the same as
condition to 'init-unix', 
> but never tested.

That's an important use case.  I'll try to test it.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com

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