@niclas @lupyuen I think the quiz covers "spec defined" and "implementation defined" behavior, and it says at the beginning, "All other things being equal, assume GCC/LLVM x86/x64 implementation-defined behaviors."
The C spec leaves some things for the implementation to decide, but any implementation needs to decide them. So a conforming program can depend on the question having *some* answer, even though the answer isn't given by the spec.
By contrast, the spec also has some behaviors as undefined, and a program that invokes undefined behavior has no guarantees at all (by the spec).
@lupyuen I am not hardcore C programmer, but I think the test is incorrect, since it on one hand asks about defined behavior, yet answers are aligned with C for x64.
I am pretty (but not totally) sure that many of the answers are not spec accurate for all bit widths of underlying architecture.