RFR: 8328874: Class::forName0 should validate the class name length early [v10]

[Guanqiang Han]

On Thu, 28 Aug 2025 13:52:37 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update Class.java
>>   
>>   avoid the case of int overflow
>
> src/java.base/share/classes/java/lang/Class.java line 4170:
> 
>> 4168:         // The check utfLen >= nameLen ensures we don't incorrectly return true in case of int overflow.
>> 4169:         int utfLen = ModifiedUtf.utfLen(name, 0);
>> 4170:         return utfLen <= JAVA_CLASSNAME_MAX_LEN && utfLen >= nameLen;
> 
> A typical overflow-conscious idiom is to subtract the unknown value from the known positive number and compare with 0.
> Suggestion:
> 
>         int utfLen = ModifiedUtf.utfLen(name, 0);
>         return JAVA_CLASSNAME_MAX_LEN - utfLen >= 0;

@RogerRiggs Good catch! Fixed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26802#discussion_r2307802875