Is python initialized more than once, somehow? Otherwise, I'd like see the values of $($(best)) and $($(self.all-flags)).
Perhaps now would be a good time to start promoting my debugger for Jam. After building b2 from the debug branch: $ b2 -dconsole (b2db) break property.jam:743 Breakpoint 1 set at property.jam:743 (b2db) run --dump-tests msvc-14.0 -n ... (b2db) print $($(best)) (b2db) print $($(self.all-flags))
Breakpoint 1, class@property-map.find ( object(property-set)@149526 ) at M:/data/boost/boost-master/tools/build/src/build\property.jam:743 743 errors.error "Ambiguous key $(properties:J= :E=)" ; (b2db) print $($(best)) (b2db) print $($(self.all-flags)) <.pyd> <python>2.5 <target-os>windows <.pyd> <python>2.5 <target-os>windows (b2db) Note that I actually have: $ python --version Python 2.7.10