cmd/cgo: -godefs mishandles enum value

[ianlancetaylor]

Reduced test case:

package p

// enum { IFF_UP = 0x1 };
import "C"

const IFF_UP = C.IFF_UP

Running go tool cgo -godefs x.go with Go 1.14 produces

const IFF_UP = 0x1

With tip it produces

const IFF_UP = int32

Although -godefs is not seriously supported, we shouldn't break it like this.

This may be due to https://golang.org/cl/230037. CC @mdempsky

[mdempsky]

I can look into it, unless you're already doing that.

[ianlancetaylor]

I'm looking at it. I have a fix.

[gopherbot]

Change https://golang.org/cl/237558 mentions this issue: cmd/cgo: in -godefs mode, don't change constant to type

[tklauser]

Thanks a lot for fixing this @ianlancetaylor. Just noticed the same behavior while trying to re-generate x/sys/unix with go1.15beta1.