[Bug libstdc++/51906] thread lock test failures on darwin11 under Xcode 4.2

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906

--- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-01-29 
00:47:05 UTC ---
also, stack trace please. it's not easy to debug problems on systems I don't
have access to when I have to guess what the program does.