How does CRuby maintain memory safety between the VM, GC, and native C extensions?

CRuby uses GC write barriers, object marking rules, and controlled APIs (like rb_gc_mark) to ensure native extensions remain safe.

CRuby must coordinate three memory domains: VM-managed Ruby objects, GC heap, and C extensions. Native extensions are required to explicitly mark Ruby objects they reference using rb_gc_mark during GC cycles. If they fail, objects may be prematurely collected. The GC uses a mark-and-sweep algorithm with write barriers to track cross-generation references. The VM enforces object validity via VALUE handles, which are abstracted pointers with embedded tagging.