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Chris Tate
232add4a3f
- A hierarchy upcast in the C backend is a raw pointer cast, so one object's rc/vt and fields are accessed through both the base and derived struct types; clang's TBAA at -O2 treated those as non-aliasing and reordered/elided the inlined rc updates, freeing an upcast-compared object while a global still owned it (SIGSEGV in sc_release_globals — a runtime miscompile, not a compile-time crash; the generated C's RC bookkeeping was already balanced). - The flag joins all three lockstep option sets: compileC's single-invocation buildArgs, the cache-miss cflags, and compileLibArchive; the cache key hashes the full command line, so stale binaries and runtime objects re-key on their own. - The LLVM backend emits no TBAA metadata, so the flag also makes the two backends' memory semantics identical instead of coincidentally so. - New differential fixture 2556-upcast-identity.ts: identity compares through a three-deep hierarchy at every view, both operand orders, !==, constructing operands on either and both sides, compares as call arguments and as standalone expression statements, and field liveness after the compares — it SIGSEGVs without the flag and is Node-exact with it on both backends, plain and sanitized.