[NaySurGithub]

Problem

Joining a server from Discord while already connected crashes the client:

libc++abi: terminating due to uncaught exception of type std::system_error: mutex lock failed: Invalid argument

The macOS crash report (EXC_CRASH / SIGABRT, render thread) stops in:

std::mutex::lock()
perlin::Perlin::FrameStep() + 18708
perlin::Perlin::RenderThreadMain()

The run log right before it shows [discord] joining nethernet.playhive.com:19132 from Discord.

Cause

In the release binary, FrameStep + 18708 is mutex::lock(live + 0xA940), right after PollJavaPack(live). That is the inlined UpdateChat → live->TakeChat(), where live is the frame's f.live session.

FrameStep runs UpdateSession(f) (which sets f.live), then UpdateDiscord(), then UpdateViewSettings and UpdateChat. A Discord join goes UpdateDiscord → HandleDiscordJoin → JoinServer → Connect(), in the middle of the frame. Connect() moved the current session into retiredSessions and then immediately ran:

if (connectsInFlight.load() == 0)
    std::erase_if(retiredSessions, [](const auto& s) { return !s->Transferring(); });

That freed the session it had just retired, while f.live still pointed at it. The rest of the frame then locked its destroyed chat mutex. The replay setup (PerlinReplay.cpp) pruned the same way. Any other mid-frame Connect() (a transfer, a menu button) has the same hazard.

Change

• Connect() and the replay session setup no longer free retired sessions.
• UpdateSession frees them at the start of a frame, before the frame takes its live session, with the same connectsInFlight / Transferring() conditions as before.

A retired session therefore always outlives the frame that retired it. The other raw session pointers are safe with this: hurtSession is only compared, never dereferenced, and modLive is reassigned every frame in PumpMods, after the prune.

Testing

• macOS arm64 Release build.
• Not tested yet: connect to a server, then join another one from Discord without leaving. That crashed before this change.