Memory & garbage collection

Unreal has two memory worlds: garbage-collected UObjects managed by the engine's GC, and ordinary C++ heap objects you manage with smart pointers or RAII. Mixing them up causes most UE crashes. The one rule that prevents the majority of them: a UObject stays alive only while something reachable from the root set holds it in a UPROPERTY (or an equivalent GC-tracked reference).

When to use this skill

• Choosing which pointer type to use for a UObject or plain C++ object.
• Crash after a few seconds or after a level load — the classic "GC collected it" symptom.
• A non-UObject class (subsystem helper, Slate widget, RAII guard) needs to keep a UObject alive.
• "Why is my pointer suddenly null or garbage?" debugging.
• Deciding between TSharedPtr, TSharedRef, TUniquePtr, or FGCObject for a new type.

See also: cpp-fundamentals for UObject/UPROPERTY/UFUNCTION macro basics; actors-and-components for actor ownership and component lifetime.