RFR: 8311939: Excessive allocation of Matcher.groups array [v7]

[Roger Riggs]

On Wed, 16 Aug 2023 09:11:34 GMT, Cristian Vat <duke at openjdk.org> wrote:

>> Reduces excessive allocation of Matcher.groups array when the original Pattern has no groups or less than 9 groups.
>> 
>> Original clamping to 10 possibly due to documented behavior from javadoc: 
>> "In this class, \1 through \9 are always interpreted as back references, "
>> 
>> Only with Matcher changes RegExTest.backRefTest fails when backreferences to non-existing groups are present.
>> Added a match failure condition in Pattern that fixes failing tests.
>> 
>> As per existing `java.util.regex.Pattern.BackRef#match`: "// If the referenced group didn't match, neither can this"
>> 
>> A group that does not exist in the original Pattern can never match so neither can a backref to that group.
>> If the group existed in the original Pattern then it would have had space allocated in Matcher.groups for that group index.
>> So a group index outside groups array length must never match.
>
> Cristian Vat has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8311939
>  - Merge branch 'openjdk:master' into JDK-8311939
>  - review condition
>  - changes and test for CIBackRef
>  - remove new line
>  - reduce allocations also for Matcher.usePattern
>  - 8311939: Excessive allocation of Matcher.groups array

LGTM

Looks good.
Non-"R"-reviewers can review and approve (and get recognition for reviewing).

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

Marked as reviewed by rriggs (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14894#pullrequestreview-1581222155
PR Comment: https://git.openjdk.org/jdk/pull/14894#issuecomment-1681106661