From ogillespie at openjdk.org Mon Dec 22 17:20:21 2025 From: ogillespie at openjdk.org (Oli Gillespie) Date: Mon, 22 Dec 2025 17:20:21 GMT Subject: RFR: 7904124: JOL: Correct mark header size for Lilliput V2 in object internals Message-ID: Before (mark header size is wrong, overlapping the first field): java.lang.String object internals: OFF SZ TYPE DESCRIPTION VALUE 0 8 (object header: mark) 0x0036449200bc8001 (Lilliput) 4 4 int String.hash 3556498 After: java.lang.String object internals: OFF SZ TYPE DESCRIPTION VALUE 0 4 (object header: mark) 0x00bc8001 (Lilliput) 4 4 int String.hash 3556498 ModelVM naively uses the address size as the mark header size, but that's not valid for Lilliput V2. Use object header size minus class header size instead (both of these are implemented for Lilliput V2). I'm not certain if this is correct in all scenarios. **Testing**: spot-checked with Lilliput off, Lilliput V1 and Lilliput V2 for String and a few other classes. Ran `mvn clean verify`. ------------- Commit messages: - 7904124: JOL: Correct mark header size for Lilliput V2 in object internals Changes: https://git.openjdk.org/jol/pull/66/files Webrev: https://webrevs.openjdk.org/?repo=jol&pr=66&range=00 Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904124 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jol/pull/66.diff Fetch: git fetch https://git.openjdk.org/jol.git pull/66/head:pull/66 PR: https://git.openjdk.org/jol/pull/66