cmd/dist: linux/riscv64 listed as supported platform

[vcabbage]

What version of Go are you using (go version)?

$ go version
go version devel +048c9164a0 Sat Nov 24 23:55:07 2018 +0000 linux/amd64

Does this issue reproduce with the latest release?

Yes, introduced in 1.11.

What operating system and processor architecture are you using (go env)?

N/A

What did you do?

Ran go tool dist list

What did you expect to see?

Only supported GOOS/GOARCH combinations listed.

What did you see instead?

linux/riscv64 listed even though it hasn't been fully implemented.

Added in https://golang.org/cl/118618. Appears it may be needed for the development of the RISC-V port but it doesn't seem as though it should be included in go tool dist list since that's documented to "list all supported platforms".

[ALTree]

Milestoning as 1.13 since the riscv GOARCH was introduced the previous development cycle (1.11), so this dist list issue is not something that needs to be acted upon for the 1.12 release.

It's not clear if dist list is supposed to print all the reserved GOOS/GOARCH pairs (and in this case it's correct to list riscv64), or just the platforms where Go is actually working.

[tklauser]

See #27532 for the state of riscv64 support. https://golang.org/cl/118618 was already sent so the Go tooling can be used to auto-generate files for linux/riscv64 in golang.org/x/sys/unix (https://golang.org/cl/133735).

[bradfitz]

I suppose we could have another incomplete map in dist alongside the cgo one and then filter out some ports in dist list.

[ncw]

I discovered this when trying to compile things with go1.12beta1

This problem has broken these tests which use go tool dist list to find all the valid architectures to test compilation:

https://github.com/a8m/tree/blob/3cf936ce15d6100c49d9c75f79c220ae7e579599/compileall.sh#L1-L14

So fixing go tool dist list to only emit GOOS/GOARCH which can be compiled would get my vote!

[ncw]

I decided to work around this problem by running go tool compile -V first to see if the architecture was supported before attempting a compile on a given GOOS/GOARCH pair.

https://github.com/a8m/tree/blob/6a0b80129de45f91880d18428b95fab29df91d7e/compileall.sh#L13-L21

[gopherbot]

Change https://golang.org/cl/155839 mentions this issue: cmd/dist: list only supported platforms