xbolva00 added a comment. In D96418#2783541 <https://reviews.llvm.org/D96418#2783541>, @leonardchan wrote:
>> Well, no, I'm afraid it is actually clear that that code does have UB >> according to the C++ standard. Perhaps you mean that it *shouldn't* have >> UB, or that Clang should define its behavior despite the standard. >> >> I might agree with you that I don't see the value in using this stronger >> rule in C++, but I think it would help to understand the problem a little >> better. I assume this is causing problems for a less trivial test case? Or >> do you really have code that's relying on that loop not terminating? > > I see. I guess it's good (and bad) that this discovered this UB in our code > base. The example I posted is almost exactly what's in our test case. For > this particular one, we need a non-terminating thread, so a thread_create > function is passed `do_nothing`. Locally, we could get around this by using > something like inline assembly to avoid UB. > > (Potentially deviating from this patch) While an infinite loop may be UB > according to the standard, it's also something fairly common that can be in a > lot of code bases. Although it may be an unintended side-effect, it still > seems a bit abrupt that we found about this UB from this patch rather than > ubsan or a compiler diagnostic. Are there any plans in the future for > something along the lines of improving catching this type of UB? Or > alternatively, are there plans of maybe defining it in clang (like a language > extension) as @rjmccall points out? I think this new optimization was mentioned in clang release notes, worth to read them. And there is a flag to disable this opt - -fno-finite-loops I think. Info about loop finiteness is useful for various optimizations so I dont know why clang should promise any behaviour. Sometime in the future you may compile your code with gcc and boom as well.. And maybe you can use this https://clang.llvm.org/extra/clang-tidy/checks/bugprone-infinite-loop.html to find infinite loops? Possibly we have compiler remark for it as well (?). Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D96418/new/ https://reviews.llvm.org/D96418 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
