[foreign-abi] RFR: 8240173: Confusing overflow error when trying to dereference a nothing segment

[Henry Jen]

On Thu, 27 Feb 2020 12:40:08 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This simple patch attempts to generate a more explicit error message when trying to dereference an address which is based on the Nothing segment. Note that the first problem here is caused by the fact that the Nothing segment is considered "small" - which means most of the real address values will fall outside its range. While we could simply fix that (which will improve the error message - from reporting an overflow during offset computation to report an access outside the bounds of the segment), I thought it was better to mark the Nothing segment as non-accessible, and generate an explicit error message.

Looks good. I think making NO_ACCESS explicit rather than depending on size checking is the right thing and glad to see the unused mask argument gone before we actually need it.

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PR: https://git.openjdk.java.net/panama-foreign/pull/34