Integrated: 8338731: MemoryLayout::offsetHandle can return a negative offset

[Maurizio Cimadamore]

On Wed, 21 Aug 2024 13:26:58 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> When working on startup improvements, I noticed that the method handle returned by `MemoryLayout::offsetHandle` can overflow if the client calls the handle with a base offset that is too big.
> 
> In other similar situations, the layout API always fails with `ArithmeticException` (see `MemoryLayout::scale`), so we should do the same here.
> 
> The fix is to use a `Math::addExact(long, long)` for the outermost add operation in the computation of the offset method handle. That outermost computation in fact is the only one that can overflow: it is an addition between a user-provided base offset `B` and a layout offset `L`. `L` is guaranteed not to overflow, by construction (as `L` is derived from a layout path). But `B` + `L` might overflow, so the new logic checks for that.

This pull request has now been integrated.

Changeset: 1ff9ac72
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/1ff9ac7233d51a58fd54a92d2c45761478574cc7
Stats:     23 lines in 3 files changed: 14 ins; 1 del; 8 mod

8338731: MemoryLayout::offsetHandle can return a negative offset

Reviewed-by: pminborg, psandoz

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PR: https://git.openjdk.org/jdk/pull/20662