Integrated: 8367585: Prevent creation of unrepresentable Utf8Entry

[Chen Liang]

On Mon, 15 Sep 2025 05:43:43 GMT, Chen Liang <liach at openjdk.org> 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.

This pull request has now been integrated.

Changeset: 3b1eb762
Author:    Chen Liang <liach at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/3b1eb7623180ac1b1d69622481589c43749dbbfc
Stats:     380 lines in 10 files changed: 210 ins; 53 del; 117 mod

8367585: Prevent creation of unrepresentable Utf8Entry

Reviewed-by: asotona

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PR: https://git.openjdk.org/jdk/pull/27281