RFR: 8314488: Compile the JDK as C++17 [v2]

[Martin Doerr]

On Fri, 15 Dec 2023 08:08:10 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> Implementation of [JEP draft: Compile the JDK as C++17](https://bugs.openjdk.org/browse/JDK-8310260)
>
> Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into patch-7
>  - Revert vm_version_linux_riscv.cpp
>  - vm_version_linux_riscv.cpp
>  - allocation.cpp
>  - 8310260

In case you want to update the required compiler versions as part of this PR: We have tested
-TOOLCHAIN_MINIMUM_VERSION_xlc="16.1.0.0011"
+TOOLCHAIN_MINIMUM_VERSION_xlc="17.1.1.4"
(Already discussed with Kim.)

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PR Comment: https://git.openjdk.org/jdk/pull/14988#issuecomment-1857916995