[Boost-build] defaults applied too early?

From: David Abrahams (dave_at_[hidden])
Date: 2007-03-21 04:11:27

I have this:

  using python : 2.5 ;
  using python : 2.4 : : : : <target-os>cygwin ;

When I build with

     bjam target-os=cygwin

BB complains of no matching python target.  AFAICT that's because it
sees the default python version is 2.5, and since none is specified on
the command line, it tries the combination

  <python>2.5,<target-os>cygwin

for which there are no python targets declared.  Before taking the
default for the <python> feature, shouldn't BB try to match targets
without considering defaults, and then see what constraints on the
defaults are implied by those targets?  In other words, since
python=2.5 wasn't in the explicit build request, but target-os=cygwin
was, I would expect BB to select the targets matching
<target-os>cygwin,<python>2.4.

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