RFR: 8297138: UB leading to crash in Amalloc with optimized builds

[Thomas Stuefe]

On Mon, 28 Nov 2022 14:40:07 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> Yeah that's a bad name. The more I look at this the more I hate it.

In the past I fervently wished for UseMallocOnly to go away. I even prepared a prototype that would provide buffer overrun checks in Arenas (enveloping each individual arena allocation), in the assumption that was why UseMallocOnly existed. The only problem I encountered was that we sometimes use Arena for packed data, where the data is accessed as an array and needs to be packed without interleaving canaries. I think HandleAreas are such an example.

It would be nice if we could just remove it. I assume only compiler people use it.

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PR: https://git.openjdk.org/jdk/pull/11320