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go/types: doesn't understands constants defined in cgo code #21712

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purpleidea opened this issue Aug 31, 2017 · 6 comments

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@purpleidea
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commented Aug 31, 2017

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

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commented Aug 31, 2017

Upstream issue btw: libvirt/libvirt-go#22

@odeke-em

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commented Aug 31, 2017

@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

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commented Aug 31, 2017

@griesemer

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commented Aug 31, 2017

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

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commented Sep 7, 2017

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

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commented Mar 29, 2018

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
)

@ianlancetaylor ianlancetaylor added this to the Unplanned milestone Mar 29, 2018

@ianlancetaylor ianlancetaylor changed the title Gotype lint error in 1.9 (worked in 1.8) go/types: doesn't understands constants defined in cgo code Mar 29, 2018

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