[libcxx-commits] [clang] [libcxx] [llvm] [CLANG][LIBCXX][LLVM] Partial program correctness. P1494R5, P3641R0 (PR #237335)

[Eli Friedman via libcxx-commits]

efriedma-quic wrote:

See the section on "Implicit approach" in the paper for why the C++ standard makes observable checkpoints separate from observable behavior.

For your new example, the defined prefix is just printing "start".  None of the other operations before the undefined behavior result in any observable behavior.  Once you hit the undefined behavior, the observed effects are arbitrary.  Printing "error" and exiting is one kind of arbitrary behavior.

https://github.com/llvm/llvm-project/pull/237335