Crash when calling simLoadLevel

[niekvleeuwen]

Bug report

• AirSim Version: latest master
• UE version: 4.25
• OS Version: Ubuntu 18.04

What's the issue you encountered?

Calling simLoadLevel results in the Unreal Engine crashing.

How can the issue be reproduced?

Call simLoadLevel. I used the following line:

bool succes = client.simLoadLevel("FlyingExampleMap");

Full error message

Assertion failed: IsInGameThread() || IsInSlateThread() [File:/home/niek/code/UnrealEngine/Engine/Source/Runtime/SlateCore/Private/Widgets/SWidget.cpp] [Line: 1067] Slate can only be accessed from the GameThread or the SlateLoadingThread!

libUE4Editor-Core.so!FGenericPlatformMisc::RaiseException(unsigned int) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/Core/Private/GenericPlatform/GenericPlatformMisc.cpp:472]
libUE4Editor-Core.so!FOutputDevice::LogfImpl(char16_t const*, ...) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/OutputDevice.cpp:61]
libUE4Editor-Core.so!AssertFailedImplV(char const*, char const*, int, char16_t const*, __va_list_tag*) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:100]
libUE4Editor-Core.so!FDebug::CheckVerifyFailedImpl(char const*, char const*, int, char16_t const*, ...) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:447]
libUE4Editor-SlateCore.so!SWidget::Invalidate(EInvalidateWidgetReason) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/SlateCore/Private/Widgets/SWidget.cpp:1067]
libUE4Editor-SlateCore.so!bool SWidget::SetAttribute<EVisibility, EVisibility>(TAttribute<EVisibility>&, TAttribute<EVisibility> const&, EInvalidateWidgetReason) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/SlateCore/Public/Widgets/SWidget.h:1506]
libUE4Editor-SlateCore.so!SCompoundWidget::SetVisibility(TAttribute<EVisibility>) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/SlateCore/Private/Widgets/SCompoundWidget.cpp:79]
libUE4Editor-UMG.so!UWidget::SetVisibility(ESlateVisibility) [/home/niek/code/UnrealEngine/Engine/Source/Runtime/UMG/Private/Components/Widget.cpp:312]
libUE4Editor-AirSim.so!WorldSimApi::loadLevel(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) [/home/niek/code/niekvleeuwen/AirSim/Unreal/Environments/Blocks/Plugins/AirSim/Source/WorldSimApi.cpp:21]
libUE4Editor-AirSim.so!std::__1::__function::__func<(lambda at /home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/include/rpc/dispatcher.inl:67:40), std::__1::allocator<(lambda at /home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/include/rpc/dispatcher.inl:67:40)>, std::__1::unique_ptr<clmdep_msgpack::v1::object_handle, std::__1::default_delete<clmdep_msgpack::v1::object_handle> > (const clmdep_msgpack::v2::object &)>::operator() [/usr/lib/llvm-8/bin/../include/c++/v1/functional:1651]
libUE4Editor-AirSim.so!rpc::detail::dispatcher::dispatch_call(clmdep_msgpack::v2::object const&, bool) [/home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/lib/rpc/dispatcher.cc:46]
libUE4Editor-AirSim.so!rpc::detail::dispatcher::dispatch(clmdep_msgpack::v2::object const&, bool) [/home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/lib/rpc/dispatcher.cc:22]
libUE4Editor-AirSim.so!clmdep_asio::detail::completion_handler<rpc::detail::server_session::do_read()::$_1::operator()(std::__1::error_code, unsigned long) const::'lambda'()>::do_complete(clmdep_asio::detail::task_io_service*, clmdep_asio::detail::task_io_service_operation*, std::__1::error_code const&, unsigned long) [/home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/dependencies/include/asio/detail/completion_handler.hpp:67]
libUE4Editor-AirSim.so!clmdep_asio::detail::task_io_service::do_run_one(clmdep_asio::detail::scoped_lock<clmdep_asio::detail::posix_mutex>&, clmdep_asio::detail::task_io_service_thread_info&, std::__1::error_code const&) [/home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/dependencies/include/asio/detail/impl/task_io_service.ipp:371]
libUE4Editor-AirSim.so!clmdep_asio::detail::task_io_service::run(std::__1::error_code&) [/home/niek/code/niekvleeuwen/AirSim/external/rpclib/rpclib-2.2.1/dependencies/include/asio/detail/impl/task_io_service.ipp:148]
libUE4Editor-AirSim.so!std::__1::__function::__func<rpc::server::async_run(unsigned long)::$_0, std::__1::allocator<rpc::server::async_run(unsigned long)::$_0>, void ()>::operator()() [/usr/lib/llvm-8/bin/../include/c++/v1/functional:1651]
libUE4Editor-AirSim.so!void* std::__1::__thread_proxy<std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, std::__1::function<void ()> > >(void*) [/usr/lib/llvm-8/bin/../include/c++/v1/thread:352]
libpthread.so.0!UnknownFunction(0x76da)
libc.so.6!clone(+0x3e)