Crash when deleting plugins

[pierreguillot]

I encounter a crash sometimes when deleting plugins, here is the stack (with one of the BBC plugins but it also happens with the Vamp example plugins):

Thread 0 Crashed:: JUCE Message Thread  Dispatch queue: com.apple.main-thread
0   libstdc++.6.dylib             	0x00007fffbff23209 std::_Rb_tree_rebalance_for_erase(std::_Rb_tree_node_base*, std::_Rb_tree_node_base&) + 433
1   bbc-vamp-plugins.dylib        	0x0000000105c9d8d9 std::_Rb_tree<void const*, std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*>, std::_Select1st<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> >, std::less<void const*>, std::allocator<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> > >::erase(std::_Rb_tree_iterator<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> >, std::_Rb_tree_iterator<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> >) + 89
2   bbc-vamp-plugins.dylib        	0x0000000105c9d97f std::_Rb_tree<void const*, std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*>, std::_Select1st<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> >, std::less<void const*>, std::allocator<std::pair<void const* const, _VampPlugin::Vamp::PluginAdapterBase::Impl*> > >::erase(void const* const&) + 79
3   bbc-vamp-plugins.dylib        	0x0000000105c9cb45 _VampPlugin::Vamp::PluginAdapterBase::Impl::~Impl() + 309
4   bbc-vamp-plugins.dylib        	0x0000000105c9cf14 _VampPlugin::Vamp::PluginAdapterBase::~PluginAdapterBase() + 36

This seems related to the m_pluginLibraryHandleMap. I load and delete plugins it in a multithread context, do you think that could be the cause?

Tested on Mac OS X 10.12.4, 10.14.6 & 10.15.6