RFR: 8331920: ubsan: g1CardSetContainers.inline.hpp:266:5: runtime error: index 2 out of bounds for type 'G1CardSetHowl::ContainerPtr [2]' reported [v2]

[Thomas Schatzl]

On Wed, 22 May 2024 07:56:15 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

>> Hi all,
>> 
>> Please review this change to improve access to G1CardSetContainer VLA elements. Instead of  straightforward indexing, we obscure access through a base pointer and offsets to reduce the possibility of UB. 
>> 
>> Testing: Tier 1-3
>>               - Local testing on Mac with `--enable-ubsan`.
>
> Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Axel suggestion

Still good.

One of the new methods could be made const, but feel free to ignore (and sorry for noticing a bit late)

src/hotspot/share/gc/g1/g1CardSetContainers.hpp line 250:

> 248:   void iterate_cardset(ContainerPtr const container, uint index, CardOrRangeVisitor& found, G1CardSetConfiguration* config);
> 249: 
> 250:   ContainerPtr at(EntryCountType index);

Could be made `const`, i.e. 
Suggestion:

  ContainerPtr at(EntryCountType index) const;

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Marked as reviewed by tschatzl (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19300#pullrequestreview-2070766179
PR Review Comment: https://git.openjdk.org/jdk/pull/19300#discussion_r1609687736