On Mon, Feb 20, 2023 at 12:18:36PM +0100, Marc Glisse via Gcc-help wrote: > On Mon, 20 Feb 2023, Gabriel Ravier via Gcc-help wrote: > > >This is the kind of thing that makes me wonder why there isn't some kind > >of `__builtin_unreachable_do_not_optimize()` builtin that allows one to > >mark places in code that should never be reached and should thus be warned > >about if such a thing happens while at the same time never doing any > >optimization on the basis of the presence of the call. > > -fsanitize=unreachable -fsanitize=null and others prevent the kind of > optimization you are worried about. Or even just __builtin_trap(), or abort(), or similar. Just a printf() thing if you really want to just warn. "Never doing any optimisation" based on <anything> is of course not a reasonable expectation; but you *can* ask for reachable code not to be optimised away. This is the default, just don't mark reachable code as unreachable :-) Segher
