sfFontStuff heap corruption

[gottfriedleibniz]

There are race conditions within HandleSprite (via drawTextStub) that is corrupting the underlying GMemoryHeapPT instance. This issue has been masked/softened by the SEH frame, but emerged elsewhere in 2944.

Since the heap is not flagged as thread-safe/critical (reference its allocation methods that include a +0xC0 check), MainThrd and Render will be fighting at several places. Additionally, the HandleSprite function itself is not particularly thread-safe (e.g., follow the CreateCharacterInstance/Reset code down to GASEnvironment interactions and the likes). Given how gross the GFx assembly is somebody else verifying this will be required.

My current workaround has been to ensure g_movie's HeapPT is flagged in HandleEarlyLoading and throwing a mutex at HandleSprite; there are likely better solutions (besides my ~6 line hack). Also, test(rax, rax) could probably be changed to eax.

A reproduction can be found on the forum.