I do agree that this isn't quite so straightforward, but I also can't see that it's necessary for the compiler to guess what is meant here. Even supposing the a

I do agree that this isn't quite so straightforward, but I also can't see that it's necessary for the compiler to guess what is meant here. Even supposing the array is initialised elsewhere there is a read past the end of the array -- I hope we'd both agree that a segfault in response is perfectly reasonable. If that's the case then maybe forcing a segfault is better than optimising the loop away, but I do err on the compiler's side here. As others have pointed out, the compiler warns that undefined behaviour is invoked by the code and it probably doesn't actually do what the author thinks it does. The diagnostic also isn't required by the standard. The clear intent of the code certainly isn't clear to me -- whatever calculation is done involving a value read from past the end of the array only tells me that the return value isn't used in any meaningful way, and if that's the case then why not eliminate the code? [EDIT] Ok, just re-read the code, I guess the value is actually unused so the function return value is presumably OK, but I think the option of the segfault is still reasonable for the compiler to do.