aaron.ballman added a comment. In D135551#3850132 <https://reviews.llvm.org/D135551#3850132>, @inclyc wrote:
> In D135551#3849983 <https://reviews.llvm.org/D135551#3849983>, @aaron.ballman > wrote: > >> In D135551#3849944 <https://reviews.llvm.org/D135551#3849944>, @inclyc wrote: >> >>>> - Prefer llvm_report_error() in any circumstance under which a code path >>>> is functionally possible to reach, but only in erroneous executions that >>>> signify a mistake on the part of the LLVM developer elsewhere in the >>>> program. >>>> - Prefer llvm_unreachable() in any circumstance under which a code path is >>>> believed to be functionally impossible to reach (even if technically >>>> possible to reach). The API is now self-documenting to mean "this code >>>> really should be totally unreachable". >>> >>> I think `llvm_unreachable` already has the functionality reporting bugs for >>> developer in our implementation, with +Assertions by default >> >> Yes, in terms of its runtime behavior. So long as we're not making debugging >> harder for some large group of people, the runtime behavior is not really >> what I'm concerned by though. I'm focusing more on code reviewers and >> project newcomers and whether our code is self-documenting or not. Having a >> policy to use an API that says code is not reachable in situations where >> that code is very much reachable is the crux of my problem -- the API is >> sometimes a lie (and a lie with optimization impacts, at that) and we force >> everyone to pay the cognitive costs associated with that when reading code. >> >> If we end up with two APIs that have the same runtime behavior, I'm okay >> with that. > > Could you elaborate on "aspirationally" vs "functionally" unreachable code > here? Sure! enum E { Zero, One, Two }; int func(E Val) { switch (Val) { case Zero: return 12; case One: return 200; case Two: return -1; } llvm_unreachable("never get here"); // Functionally unreachable; we can't think of a reasonable way to get here without other alarms going off } vs enum E { Zero, One, Two }; extern "C" int func(unsigned Val) { switch (Val) { case Zero: return 12; case One: return 200; case Two: return -1; } assert(0 && "never get here"); // Aspirationally unreachable; we HOPE we don't get here but it's plausible that we do if someone made a logical mistake calling the API } Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D135551/new/ https://reviews.llvm.org/D135551 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
