On 2014-11-23 8:16 AM, Tom Kent wrote:
Starting somewhere between 2014-11-21 09:38:32 and 14:07:31 (pacific time) all the tests (on develop?) started failing.

...

The end of results/bjam.log are:
D:/local/teeks99-08/e/boost_bb/src/build\feature.jam:139: in feature.feature from module feature
error: feature already defined:
error: in feature declaration:
error: feature "segmented-stacks" : "on" : "optional" "propagated" "composite"
...

Same symptoms for me, develop branch. Master branch worked. MinGW-w64-4.6 was the specific platform.