Thread is still failing test_tss_lib, now with this... ../libs/thread/test/test_tss.cpp(181): error in "test_tss": Support of automatic tss cleanup for native threading API not available If I understand this correctly, the tss cleanup will never be called for a thread created via the native API. There's no global function that can force a clean-up because nothing can force the underlying thread mechanism to return the thread-specific value for a thread that's already exited. I see some subtle magic in libs/thread/src/win32/tss_pe.cpp, some even for __MINGW32_... Is this for static libs? Any chance we can make that work for MinGW's gcc-4.3.3 and gcc-4.4.0? Also, I think the docs need a "Note" section describing this issue, say thread_local_storage.html, inside the section "Cleanup at thread exit".