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Startup crash in Shipping builds running on Steam

There is a known bug in Epic's implementation of Steam, which causes Steam events to fire on a separate thread before the online subsystem infrastructure has fully initialized. This causes a crash because the online subsystem infrastructure attempts to initialize Steam again while it is already initializing.

To resolve this issue, you currently need to patch the engine source code. At the plugin level, we plan on re-implementing Steam ourselves and no longer relying on the engine's implementation, but this is a large undertaking. The issue which tracks that body of work can be found on GitLab (sign in required).

Patch OnlineSubsystemSteam.cpp​

Locate Engine\Plugins\Online\OnlineSubsystemSteam\Source\Private\OnlineSubsystemSteam.cpp in the engine installation.

Within this file, locate the FOnlineSubsystemSteam::Init function and then replace the following lines of code:

// Create the online async task thread
OnlineAsyncTaskThreadRunnable = new FOnlineAsyncTaskManagerSteam(this);
check(OnlineAsyncTaskThreadRunnable);
OnlineAsyncTaskThread = FRunnableThread::Create(OnlineAsyncTaskThreadRunnable, *FString::Printf(TEXT("OnlineAsyncTaskThreadSteam %s"), *InstanceName.ToString()), 128 * 1024, TPri_Normal);
check(OnlineAsyncTaskThread);
UE_LOG_ONLINE(Verbose, TEXT("Created thread (ID:%d)."), OnlineAsyncTaskThread->GetThreadID() );

with the fixed version:

// Create the online async task thread
OnlineAsyncTaskThreadRunnable = new FOnlineAsyncTaskManagerSteam(this);
check(OnlineAsyncTaskThreadRunnable);
FTSTicker::GetCoreTicker().AddTicker(FTickerDelegate::CreateLambda([this](float) -> bool {
    OnlineAsyncTaskThread = FRunnableThread::Create(OnlineAsyncTaskThreadRunnable, *FString::Printf(TEXT("OnlineAsyncTaskThreadSteam %s"), *InstanceName.ToString()), 128 * 1024, TPri_Normal);
    check(OnlineAsyncTaskThread);
    UE_LOG_ONLINE(Verbose, TEXT("Created thread (ID:%d)."), OnlineAsyncTaskThread->GetThreadID());
    return false;
}), 0.0f);

This will delay the dispatch of any Steam events by one frame, which ensures that Steam is fully initialized before any events are dispatched.