[foreign-memaccess+abi] RFR: 8294986: Possible mismatched acquire/release in binding specializer

[Jorn Vernee]

On Tue, 11 Oct 2022 14:47:31 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> We acquire sessions of address parameters before a downcall, and release them afterwards. However, if acquire fails with an exception, we still call release in the finally block.
> 
> Fixing this is a simple case of switching 2 lines: when acquire fails, we don't store the session in a local, and so the cleanup in the finally block will not call release on it either.
> 
> For testing, I doesn't seem possible to make this bug result in an error with the current code. So, I've added an assert to the implementation that checks whether release was called too many times.

I've removed the use of assert in favor of an explicit check. In the case of too many releases the exception message will be: `Session is acquired by -1 clients` I think that is probably good?

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PR: https://git.openjdk.org/panama-foreign/pull/739