RFR: 8321533: Clang build for Windows

[Julian Waters]

On Fri, 8 Dec 2023 09:46:59 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

> > Is it possible to fold clang-cl into the microsoft toolchain instead, and just pass clang-cl as the compiler instead of cl?
> 
> I suppose it's possible; clang-cl output is supposed to be compatible with link & lib, and most command line options are similar.
> 
> The thing is, when it comes to warning control, only W0-W4 are somewhat similar between clang-cl and microsoft; other than that, clang-cl accepts the same options as the regular clang. Folding clang-cl into microsoft would leave us with no way to suppress warnings.

My main concern is that this occludes clang proper, if and when that becomes a thing. If so, the clcl options might become a little redundant when compared with the existing clang option. Maybe there can be some specialized code to detect if microsoft is really clang-cl in disguise, or perhaps this could use the clang option that we already have in the build system, and then have --with-toolchain-type=clang mean either clang-cl or clang proper when the platform is Windows

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PR Comment: https://git.openjdk.org/jdk/pull/17019#issuecomment-1846906553