go/types: doesn't understands constants defined in cgo code

[purpleidea]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9 linux/amd64

Does this issue reproduce with the latest release?

Yes, fails with git tip as well.

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

GOARCH="amd64"

GOBIN=""

GOEXE=""

GOHOSTARCH="amd64"

GOHOSTOS="linux"

GOOS="linux"

GOPATH="/home/travis/gopath"

GORACE=""

GOROOT="/home/travis/.gimme/versions/go1.9.linux.amd64"

GOTOOLDIR="/home/travis/.gimme/versions/go1.9.linux.amd64/pkg/tool/linux_amd64"

GCCGO="gccgo"

CC="gcc"

GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build036482233=/tmp/go-build -gno-record-gcc-switches"

CXX="g++"

CGO_ENABLED="1"

CGO_CFLAGS="-g -O2"

CGO_CPPFLAGS=""

CGO_CXXFLAGS="-g -O2"

CGO_FFLAGS="-g -O2"

CGO_LDFLAGS="-g -O2"

PKG_CONFIG="pkg-config"

What did you do?

100% reproducible. Travis link:

https://travis-ci.org/purpleidea/mgmt/jobs/270103895#L969

(errors are on the subsequent lines)

What did you expect to see?

No failures or a clear reason about what's wrong.

What did you see instead?

gotype fails where it didn't fail in golang 1.8
it would be great to report this as a false positive or to understand what changed between 1.8 and 1.9 that this is an issue.

Thanks!
James

[purpleidea]

Upstream issue btw: libvirt/libvirt-go#22

[odeke-em]

@purpleidea, thanks for the report! Unfortunately the Go1.9 ship has sailed(it would have been nice to report this earlier) but perhaps this could be a candidate for Go1.9.1 if easily fixable within the cycle. Also it might help with easier diagnosis and fixing if you could extract a reproducible code snippet then paste it here.

/cc @griesemer.

[purpleidea]

It's 100% easy to reproduce, just run gotype on the libvirt package :) As seen in my travis example. as for 1.9.1 that would be fine, good idea!

…

On Thu, Aug 31, 2017 at 3:50 AM, Emmanuel T Odeke ***@***.***> wrote: @purpleidea <https://github.com/purpleidea>, thanks for the report! Unfortunately the Go1.9 ship has sailed(it would have been nice to report this earlier) but perhaps this could be a candidate for Go1.9.1 if easily fixable within the cycle. Also it might help with easier diagnosis and fixing if you could extract a reproducible code snippet then paste it here. /cc @griesemer <https://github.com/griesemer>. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#21712 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAIPsyVmxBz7vXtlc5d0XohnoNkCboGEks5sdmXSgaJpZM4PIVh-> .

[griesemer]

The major thing that changed for 1.9 is that gotype now uses a source importer. Can you try to run gotype with the flag -c=gc and see if the problem goes away?

[orivej]

This example fails the check unless -c=gc is specified:

package main

import "github.com/veandco/go-sdl2/sdl"

func main() {
	sdl.PeepEvents(nil, sdl.GETEVENT, sdl.FIRSTEVENT, sdl.LASTEVENT)
}

with the message

main.go:6:22: cannot use sdl.GETEVENT (constant unknown with invalid type) as github.com/veandco/go-sdl2/sdl.EventAction value in argument to sdl.PeepEvents
main.go:6:36: cannot use sdl.FIRSTEVENT (constant unknown with invalid type) as uint32 value in argument to sdl.PeepEvents
main.go:6:52: cannot use sdl.LASTEVENT (constant unknown with invalid type) as uint32 value in argument to sdl.PeepEvents

[ianlancetaylor]

The problem here is using go/types with cgo code. Is that supposed to work these days?

I can recreate the problem with

> go get -d github.com/veandco/go-sdl2/sdl
> go run ~/go/src/go/types/gotype.go -- foo.go

where foo.go is the file mentioned above. That prints

foo.go:6:22: cannot use sdl.GETEVENT (constant unknown with invalid type) as github.com/veandco/go-sdl2/sdl.EventAction value in argument to sdl.PeepEvents
foo.go:6:36: cannot use sdl.FIRSTEVENT (constant unknown with invalid type) as uint32 value in argument to sdl.PeepEvents
foo.go:6:52: cannot use sdl.LASTEVENT (constant unknown with invalid type) as uint32 value in argument to sdl.PeepEvents
exit status 2

The constants are all defined with cgo code like:

const (
	GETEVENT  = C.SDL_GETEVENT
)