BlockingMessage accessing MessageManager::Lock that went out of scope

[reuk]

I believe that this issue should be fixed in 7.0.8, but I’d recommend testing it to make sure.

The most recent changes to the MessageManager Lock were made to address these issues:

DemoRunner Multithreading Demo crashes after 5-10 minutes

DemoRunner 7.0.3 - if you run the Multithreading Demo, just let the default initial screen of moving balls run for 5-10 minutes, DemoRunner crashes. This was on MacOS Mojave 10.14.6. Crash log attached: crashlog.txt (78.9 KB) I then took the PIP of the Multithreading Demo and ran it on Xcode/Mojave. It didn’t crash as quickly, but a few hours later it hit a SIGABRT: libc++abi.dylib: terminating with uncaught exception of type std::__1::system_error: mutex lock failed: Invalid argument [mul…

Race condition (i.e. CRASH) in MessageManager::Lock (with fix!)

Scenario We run all our plugins through pluginval. Occasionally we pluginval fails when fuzzing the parameters of the VST3 versions of our plugins. The output is: Starting test: pluginval / Fuzz parameters... Exception: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) The call-stack is: [...] juce::WaitableEvent::signal() const juce_WaitableEvent.cpp:62 [Inlined] juce::MessageManager::abort() const juce_MessageManager.cpp:404 [Inlined] juce::MessageManager::messageCallback(…