RFR: 8328874: Class::forName0 should validate the class name length early [v13]

[Guanqiang Han]

On Thu, 4 Sep 2025 14:42:40 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Guanqiang Han 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 16 additional commits since the last revision:
>> 
>>  - move common method into a common file.
>>  - Merge remote-tracking branch 'upstream/master' into 8328874
>>  - Update Class.java
>>    
>>    change overflow check
>>  - Update Class.java
>>    
>>    Simplify length check
>>  - Update Class.java
>>    
>>    avoid the case of int overflow
>>  - Update Class.java
>>    
>>    Use ModifiedUtf.utfLen instead of static import for readability
>>  - change copyright year
>>  - a small fix
>>  - add regression test
>>  - Merge remote-tracking branch 'upstream/master' into 8328874
>>  - ... and 6 more: https://git.openjdk.org/jdk/compare/edb7a478...edc1694d
>
> src/java.base/share/classes/jdk/internal/util/ModifiedUtf.java line 87:
> 
>> 85:             return true;
>> 86:         }
>> 87:         // Check exact Modified UTF-8 length.
> 
> Before doing that, I recommend another fast path `if (nameLen > MAX_LEN) return false`.

@liach I was thinking whether it might be better to place **if (nameLen > MAX_LEN) return false** after the **if (nameLen <= MAX_LEN / 3) return true** check, since in most cases nameLen will be smaller than MAX_LEN / 3 and this order would optimize for the common case.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26802#discussion_r2322673732