RFR: 8299580: RISC-V: fail to build with GCC 12 due to stringop-overflow warning

[Kim Barrett]

On Fri, 6 Jan 2023 07:36:17 GMT, Fei Yang <fyang at openjdk.org> wrote:

> > A similar problem has shown up on linux-aarch64 - https://bugs.openjdk.org/browse/JDK-8294031. I've linked the two bugs.
> > It's very interesting that something like this is appearing on multiple platforms. I've been looking at JDK-8294031 on the assumption that it was aarch64-specific. And it sure does look like a gcc bug.
> 
> Note that there might be some subtle difference here. I see this issue only triggers when we implement PlatformAdd with builtin __atomic_add_fetch on RISC-V with GCC-12. It does not trigger when we use __atomic_load for PlatformOrderedLoad. So I am not touching PlatformOrderedLoad in this PR.

I think it's the same problem, but perhaps with some platform-specific bits.  This is being discussed internally to
Oracle right now.  I suggest not making this change just yet.  It's unclear that such workarounds will really address
the fundamental problem; they _might_ provide a stop gap for a given version of gcc.

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PR: https://git.openjdk.org/jdk/pull/11858