Matt Arant
d058322cc6
Every crash root-caused earlier tonight (Subscription::subscribers, TCPServer::sessions, the Socket::write()/eventReceived() re-arm race) was the same underlying shape: some thread calling a method - or Thread::run() calling delete - on a TCPSession* while another thread concurrently freed that same object, because nothing actually guaranteed the object stayed alive for the duration of a call. Mutex-based patches at each individual call site kept narrowing the window without closing it (confirmed live, repeatedly, via AddressSanitizer under concurrent load - each fix produced a new, different crash signature at the same underlying race), and adding more locks around every write() call also works against the fifo-based design's own goal: no thread should have to block just to hand a message to another thread's session. TCPSession now derives from std::enable_shared_from_this<TCPSession> and exposes pin() - a safe upgrade from a stored raw pointer to a real, ownership-extending shared_ptr, returning nullptr instead of throwing once the object's real owner has let go. TCPServer::sessions is now the one real strong-owning shared_ptr<TCPSession> per live session; every other place that stores a TCPSession* (Subscription::subscribers, Zephora's own sessionsByPlayerName, GroupObject's membership list, etc.) is just a non-owning observer and must pin() before touching the object. A second, distinct problem: Thread::run()'s epoll dispatch starts from a raw void* of unknown validity. An early version of this fix used dynamic_cast<TCPSession*> to identify session objects before calling pin() - confirmed live via AddressSanitizer that dynamic_cast itself segfaults on a stale pointer, since it has to read the (potentially freed) object's own vtable to work at all. TCPSession::tryGet()/TCPServer:: isKnownListeningSocket() replace that: both look the raw pointer up as a key in a registry, never dereferencing it for the check itself - safe to call on any value, live session, immortal listening socket, or fully freed garbage alike. Verified via an AddressSanitizer-instrumented build under sustained concurrent load (up to 15-way parallel connect/subscribe/create/disconnect cycles, multiple rounds, 100+ total connections) with zero errors, then against the real production build with a genuine 500-connection load test (463/500 succeeded; the rest hit the process's own file-descriptor ulimit under peak burst, an unrelated and separately deferred tuning matter, not a crash). Files touched: TCPSession.h (enable_shared_from_this, pin(), the tryGet() registry), TCPServer.h/.cpp (sessions as shared_ptr, isKnownListening Socket() registry, lock made protected for subclasses), Thread.cpp (the whole dispatch rewrite), Subscription.cpp/SubscriptionManager.cpp (every subscriber write() site now pin()s first), ConsoleServer.cpp (logSend() was iterating `sessions` with no lock at all - fixed alongside the type change it needed anyway).