We released bug fix release of nghttp2 v0.6.4. It still implements h2-14 and HPACK-09.
This release fixes the application (nghttpd, nghttpx and h2load) crash with libc++ when threading is enabled. This crash was caused because of heap-use-after-free of std::mutex object. Interestingly, libstdc++ did not exhibit this issue and clang address sanitizer also did not report anything. Hopefully, this release fixes the reported crash in Mac OS X (since it is likely to use libc++), and Mac OS X users finally get multi-threaded nghttp2 applications. So try building nghttp2 without –disable-threads and run one of applications and see they do not crash.