RFR: 8314488: Compile the JDK as C++17 [v5]

[Julian Waters]

On Thu, 11 Jan 2024 12:47:25 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> @TheRealMDoerr The adlc build is notoriously problematic, since it does not share the common flags set for JVM or JDK native compilation. :( So your suggestion sounds highly likely to me. Running with LOG=cmdlines will confirm this.
> 
> (This can be done on GHA by manually starting a run, and setting the value of "Additional make arguments" to `LOG=cmdlines` or possibly `LOG=info,cmdlines`)

Doesn't ADLC share the same compilation standard options as the rest of the codebase though? https://github.com/openjdk/jdk/blob/e5aed6be7a184a86a32fa671d48e0781fab54183/make/autoconf/flags-cflags.m4#L587



> > @TheRealMDoerr The adlc build is notoriously problematic, since it does not share the common flags set for JVM or JDK native compilation. :( So your suggestion sounds highly likely to me. Running with LOG=cmdlines will confirm this.
> > (This can be done on GHA by manually starting a run, and setting the value of "Additional make arguments" to `LOG=cmdlines` or possibly `LOG=info,cmdlines`)
> 
> Thanks for the hint! The command line is also shown here: make-support/failure-logs/hotspot_variant-server_tools_adlc_objs_adlparse.o.cmdline The -std option is not passed. That seems to be the issue. So, this is not a clang 13 vs 14 thing.

Something is very wrong in that case, they're supposed be be set here: https://github.com/openjdk/jdk/blob/e5aed6be7a184a86a32fa671d48e0781fab54183/make/hotspot/gensrc/GensrcAdlc.gmk#L54

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PR Comment: https://git.openjdk.org/jdk/pull/14988#issuecomment-1887106666