Yes, it can crash, because this leads to undefined behaviour. Try to search for a number that's not in the array, what will it return? I've tested in a Ubuntu machine, with g++ (it returns 6) and clang++ (Illegal instruction error), but as all undefined behaviours, this can vary a lot. IMO, you should worry more about writing clear/semantic/correct code instead of "it works" code. Does it make sense to not return anything if an element is not found? Sometimes you "know" it won't reach the non-return point, but that's not your case - if the number is not in the array, it won't return anything (one common approach is to return an invalid index, such as -1, to indicate the "not found" situation - returning zero is wrong because it means that the element is in the first position). And the loop condition should be i < n, not <= :-)

Regarding warnings, they're usually meant to tell you "Hey, there's something strange here, you should take a look". You shouldn't ignore them, unless there's a very good reason - which is not the case of your code, IMO.