On 16/06/2021 14:36, Xi Ruoyao wrote:
> On Wed, 2021-06-16 at 14:01 +0100, Jonny Grant wrote:
>
>> Chris Latner also mentioned integer overflow being undefined, that
>> crops up too. There's no easy solution right, we need to hand write
>> code the checks? It's human-error prone if we need to manually code
>> each check. throwing in C++, or handling in C.
>>
>> if(N >= INT_MAX)
>> {
>> throw std::overflow_error("N >= INT_MAX would overflow in for
>> loop");
>> }
>>
>> for (i = 0; i <= N; ++i)
>> {
>> // ...
>> }
>
> For debugging use -fsanitize=undefined.
>
> And this is buggy anyway, no matter if there is an UB:
>
> for (unsigned i = 0; i <= N; i++)
> make_some_side_effect_without_any_undefined_behavior(i);
>
> If N may be UINT_MAX, this is not UB, but a dead loop. Programming is
> just human-error prone, even if you use "some programming language
> claimed to be able to eliminate many human errors" (I'll not say its
> name, to prevent a flame war).
>
Hi Xi
Checking the UINT_MAX would at least prevent the continual running of any such buggy loop where it increments right? and the code within the loop does not modify 'i'
for (unsigned i = 0; (i <= N) && (i != UINT_MAX); i++)
make_some_side_effect_without_any_undefined_behavior(i);
Is there any way to have a way to make loop variables like this 'i' const within the body of the loop, to avoid accidental changing of 'i' by the body of the loop
Jonny
