RFR: 8328874: Class::forName0 should validate the class name length early [v9]

[ExE Boss]

On Thu, 28 Aug 2025 02:13:52 GMT, Jason Mehrens <duke at openjdk.org> wrote:

>> Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update Class.java
>>   
>>   Use ModifiedUtf.utfLen instead of static import for readability
>
> src/java.base/share/classes/java/lang/Class.java line 4163:
> 
>> 4161:         // Quick approximation: each char can be at most 3 bytes in Modified UTF-8.
>> 4162:         // If the string is short enough, it definitely fits.
>> 4163:         if (name.length() * 3 <= JAVA_CLASSNAME_MAX_LEN) {
> 
> Won't this incorrectly return true on overflow?

Yeah, it’s better to check if `name.length() <= JAVA_CLASSNAME_MAX_LEN / 3`, probably faster too as the latter constant folds the value of `JAVA_CLASSNAME_MAX_LEN / 3`.
Suggestion:

        if (name.length() <= JAVA_CLASSNAME_MAX_LEN / 3) {

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PR Review Comment: https://git.openjdk.org/jdk/pull/26802#discussion_r2306046574