cmd/internal/sys: BuildModeSupported reports c-shared is unsupported on windows/arm64 port, which supports cgo

[dmitshur]

At tip, sys.BuildModeSupported(runtime.Compiler, "c-shared", "windows", "arm64") reports false.

https://tip.golang.org/doc/go1.17#windows suggests the windows/arm64 port supports cgo, and discussion in CL 323970 CL 323992 points out that cgo support may imply that c-shared build mode should also be turned on, and possibly was missed. This issue is filed to ask and find out.

@rsc, do you know if sys.BuildModeSupported working as intended for Go 1.17 or does it need to be updated?

[cherrymui]

Supporting cgo doesn't necessarily mean c-shared build mode is supported, so the code in cmd/internal/sys isn't necessarily wrong. We have a few other platforms that support cgo but not c-shared build mode.

It might be that the c-shared mode "just works". We'd need to test it to be sure. But it may not work, and that is fine.

[cherrymui]

and discussion in CL 323970 points out that cgo support may imply that c-shared build mode should also be turned on

I'm not sure how that CL is relevant to cgo or c-shared mode...

[dmitshur]

Thanks for answering Cherry. That suggests the current behavior of sys.BuildModeSupported is okay, and there can be a separate issue to track adding support for c-shared build mode for the windows/arm64 port.

I'm not sure how that CL is relevant to cgo or c-shared mode...

Sorry, I pasted the wrong CL number. Edited to say CL 323992 now.

I think we can close this since the original question is answered, and can reopen if more discussion is needed.