On Mon, 15 Sep 2025 05:43:43 GMT, Chen Liang <[email protected]> wrote:

> John Rose suggests in 
> https://github.com/openjdk/jdk/pull/26802#issuecomment-3201402304 that 
> ClassFile API should validate Utf8Entry length eagerly upon construction. 
> Currently we validate upon writing to bytes, which avoids validation 
> overhead. However, given that most class file utf8 data are shorter than 1/3 
> of the max length, which is always an encodable length, the performance 
> impact should be low.
> 
> Preventing the creation of unrepresentable UTF8 entries can prevent passing 
> such invalid instances around, making such problems easier to debug than a 
> failure at building.
> 
> Tier 1-3 seems clear. The performance impact to jdk.classfile.Write or any of 
> the regularly run transformation benchmarks seems neutral, less than 5% 
> perturbations.
> 
> I will update docs to reflect this change, given how widespread this is 
> across JDK - it seems the only exempt classes are Signature, ClassSignature, 
> and MethodSignature.

Early checking is good!

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PR Review: https://git.openjdk.org/jdk/pull/27281#pullrequestreview-3282616530

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