On Tue, 1 Sep 2026 06:22:48 GMT, Yunbo Zhang <[email protected]> wrote:

> Please review this small fix.
> 
> **Problem:**
> 
> `MethodHandles.foldArguments` throws `ArrayIndexOutOfBoundsException` instead 
> of `IllegalArgumentException` for negative `pos` values, which violates the 
> API's exception contract. Extreme values such as `Integer.MAX_VALUE` can also 
> overflow the existing addition-based bounds check.
> 
> **Fix:**
> 
> Validate that `foldPos` is non-negative and use:
> 
> 
> foldPos <= targetType.parameterCount() - foldVals - foldArgs
> 
> 
> **Testing:**
> 
> - Added tests for invalid positions and the valid boundary case where a 
> zero-argument `void` combiner is folded at the end of the target parameter 
> list.
> - `make test TEST=test/jdk/java/lang/invoke`: 198 passed, 4 excluded, 0 
> failed.
> 
> ---------
> - [x] I confirm that I make this contribution in accordance with the [OpenJDK 
> Interim AI Policy](https://openjdk.org/legal/ai).

Thanks for fixing this! The changes look good, but this will also need a CSR.

test/jdk/java/lang/invoke/FoldTest.java line 105:

> 103:                 Integer.MAX_VALUE
> 104:         };
> 105:         for (int pos : invalidPositions) {

I suggest using `@ParameterizedTest` as that would still run all the cases 
instead of a failure.

-------------

PR Review: https://git.openjdk.org/jdk/pull/32618#pullrequestreview-5304595400
PR Review Comment: https://git.openjdk.org/jdk/pull/32618#discussion_r4093743949

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