RFR: 8347426: Invalid value used for enum Cell in iTypeFlow::StateVector::meet_exception [v2]

[Marc Chevalier]

On Thu, 27 Feb 2025 08:28:57 GMT, Marc Chevalier <duke at openjdk.org> wrote:

>> As guess on the JBS ticket, we have a UB when `_outer->max_locals() == 0`, because then we try to do `(Cell)(-1)` which is out of range since Cell's range is [0, `INT_MAX`].
>> 
>> The obvious fix that is
>> 
>> Cell limit = local(_outer->max_locals());
>> for (Cell c = start_cell(); c < limit; c = next_cell(c)) {
>> 
>> since `local` asserts its argument to be in [0, `outer->max_locals()`). Of course
>> 
>> Cell limit = (Cell)(_outer->max_locals());
>> 
>> would work, but it seems to break (the very light) abstraction.
>> 
>> I've also added an assert to transform the UB into a clear failure.
>> 
>> This fix makes the UB warning go away on Mac with arm64.
>> 
>> Thanks,
>> Marc
>
> Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Introduce local_limit_cell

Thanks @dean-long and @vnkozlov

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PR Comment: https://git.openjdk.org/jdk/pull/23772#issuecomment-2688668804