x/sys/cpu: should HWCap and HWCap2 be exported?

[mundaym]

Are cpu.HWCap and cpu.HWCap2 supposed to be exported as part of the cpu API? I can't see any discussion about this in CL 150718 where they were added. Presumably they should be properly documented if they are supposed to be exposed.

They are only exposed on non-x86 Linux machines so I expect we could just un-export them if they aren't supposed to be exported...

[tklauser]

I suspect these were exported because the implementation was based on internal/cpu from the standard library where they need to be exported to be used in runtime.

IMO it would be fine to unexport them, also given the following comment:

// These are initialized in cpu_$GOARCH.go
// and should not be changed after they are initialized.

https://github.com/golang/sys/blob/d0b11bdaac8adb652bff00e49bcacf992835621a/cpu/cpu_linux.go#L23-L24

/cc @ianlancetaylor @bradfitz

[ianlancetaylor]

I agree.

[martisch]

I also agree to make them unexported. They are an implementation detail that should not have be exposed and it is hard to impossible to know from the outside if the value is valid/initialized.

[gopherbot]

Change https://golang.org/cl/163004 mentions this issue: cpu: unexport HWCap and HWCap2