RFR: 8345580: Remove const from Node::_idx which is modified [v2]

Emanuel Peter epeter at openjdk.org
Wed Jan 8 13:32:45 UTC 2025


On Wed, 18 Dec 2024 14:36:11 GMT, Yagmur Eren <duke at openjdk.org> wrote:

>> `Node::_idx` is declared as `const`, however, it is modified by `Node::set_idx`. Please see: https://github.com/openjdk/jdk/blob/166c12771d9d8c466e73a9490c4eb1fc9a5f6c24/src/hotspot/share/opto/node.hpp#L588
>> 
>> As already stated in [JDK-8345580](https://bugs.openjdk.org/browse/JDK-8345580) issue, this behavior is counterintuitive because a const variable is expected to remain unmodified throughout its lifetime. Additionally, C++ International Standard states that "_...any attempt to modify a `const` object during its lifetime results in undefined behavior._ ". 
>> To address this, `const` should be removed from the declaration of `Node::_idx` to align with its intended use and avoid violating the C++ standard. Tested with tier1,2,3,4,5.
>
> Yagmur Eren has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove casting trick in set_idx

@nelanbu Looks good to me, testing is passing.

I would like a second reviewer to approve it though.

-------------

Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22646#pullrequestreview-2537151678


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