RFR: 8314488: Compile the JDK as C++17 [v6]

[Magnus Ihse Bursie]

On Thu, 11 Jan 2024 13:23:45 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> Compile the JDK as C++17, enabling the use of all C++17 language features
>
> Julian Waters has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Require clang 13 in toolchain.m4

We have been stuck on a very old gcc for a long time, due to various reasons. Partly because old gcc versions were not as terrible as old versions of cl.exe, and partly to support odd linux platforms where newer gcc versions were not available.

It is tempting to raise the bar to get better functionality available on all platforms. In the end, it is a balance between supporting older platforms, and getting a better common language level for the code. 

gcc 10 was released 3+ years ago. I guess that is good enough to consider it a reasonable new minimum.

I will make a separate announcement on the build-dev list to draw attention to the fact that we want to raise minimum compiler versions, which might not be apparent from the title of this PR, to give folks a better chance at voicing concerns.

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PR Comment: https://git.openjdk.org/jdk/pull/14988#issuecomment-1895603901