RFR: JDK-8282532: Add option to explicitly set build platform and remove support for legacy cross compilation flags

[Thomas Stuefe]

On Wed, 2 Mar 2022 08:33:58 GMT, TheShermanTanker <duke at openjdk.java.net> wrote:

> > > This also removes support for the legacy cross compilation flags as well.
> > 
> > 
> > Hi,
> > without reading through building.md and your patch, which legacy flags are would be removed by this?
> > Thanks, Thomas
> 
> Specifically the flags that are checked if openjdk-target is specified, in make/autoconf/configure (Essentially just passing --build, --host and --target directly to configure, something which is largely discouraged within the JDK):
> 
> ```
> if test "x$conf_legacy_crosscompile" != "x"; then
>   if test "x$conf_openjdk_target" != "x"; then
>     echo "Error: Specifying --openjdk-target together with autoconf"
>     echo "legacy cross-compilation flags is not supported."
>     echo "You specified: --openjdk-target=$conf_openjdk_target and $conf_legacy_crosscompile."
>     echo "The recommended use is just --openjdk-target."
>     exit 1
>   else
>     echo "Warning: You are using legacy autoconf cross-compilation flags."
>     echo "It is recommended that you use --openjdk-target instead."
>     echo ""
>   fi
> fi
> ```

Okay, thank you for explaining. I cannot comment on those since I don't use them.

> 
> > Oh, and please describe whatever you do in the JBS issue. It's completely blank. It would be nice if it contained a description of what you do, at least as good as the PR text. Thank you!
> 
> Will do, thanks for the heads up!

Sure :) For most of us, JBS is the main source of information and archiving, so we try to keep its content high quality. I usually beef out the JBS issue text first and just paste that one verbatim into the PR description for the convenience of reviewers.

Did you discuss this first on the build-dev mailing list? I may have missed this discussion. If not, this is often a good first step, especially seeing that you are new. It prevents frustration later, e.g. when you code in the wrong direction.

Another small tip is to use draft PRs. Especially with build changes, it makes sense to create the PR as Draft, then wait for the GHAs to complete successfully on all platforms, and only then un-draft the PR. (e.g. with your patch, I see already failures on 32-bit). That prevents MLs being flooded by skara for work which is still in progress.

Cheers, and welcome to the OpenJDK!

..Thomas

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PR: https://git.openjdk.java.net/jdk/pull/7656