cmd/cover: internal error: overlapping blocks for func literals in switch cases

[stevekuznetsov]

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

   $ go version
   go version go1.6.2 linux/amd64
   

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

   $ go env
   GOARCH="amd64"
   GOBIN=""
   GOEXE=""
   GOHOSTARCH="amd64"
   GOHOSTOS="linux"
   GOOS="linux"
   GOPATH="/data"
   GORACE=""
   GOROOT="/usr/lib/golang"
   GOTOOLDIR="/usr/lib/golang/pkg/tool/linux_amd64"
   GO15VENDOREXPERIMENT="1"
   CC="gcc"
   GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0"
   CXX="g++"
   CGO_ENABLED="1"
   

3. What did you do?
   I ran the OpenShift Origin unit tests. Unfortunately this is fairly complicated, but can be achieved with:

   $ git clone git@github.com:openshift/origin.git
   $ cd origin
   $ make build
   $ JUNIT_REPORT=true TEST_KUBE=true hack/test-go.sh

4. What did you expect to see?
   A successful test run with no errors.

5. What did you see instead?
   Full output to stdout and stderr

   [WARNING] `go test` had the following output to stderr:
   # cover github.com/openshift/origin/vendor/k8s.io/kubernetes/pkg/client/restclient
   cover: internal error: block 264 overlaps block 266
     /data/src/github.com/openshift/origin/_output/local/go/src/github.com/openshift/origin/vendor/k8s.io/kubernetes/pkg/client/restclient/request.go:#27640,#27764 /data/src/github.com/openshift/origin/_output/local/go/src/github.com/openshift/origin/vendor/k8s.io/kubernetes/pkg/client/restclient/request.go:#27685,#27704
   

   The file mentioned above can be seen here: request.go.

I'm happy to do more digging but I'm not really sure what the #27640 syntax means or what to look for in the source.

[quentinmit]

@stevekuznetsov I believe the "#27640,#27764" means that the block begins at byte 27640 in the file and ends at byte 27764. So something like "head -c 27764 request.go | tail -c +27640" should print the block it's talking about.

Can you try again with Go 1.7rc3? It's possible that this has already been fixed since 1.6.2. Thanks!

[stevekuznetsov]

I'm afraid I can't install golang-1.7.0-rc3 on our CI super easily so I'm not sure if I can run it on the newer version without also changing other environmental stuff, but I'll give it a shot. Until then:

$ head -c 27764 vendor/k8s.io/kubernetes/pkg/client/restclient/request.go | tail -c +27640 > debug.go

// debug.go
    case bytes.IndexFunc(body, func(r rune) bool { return r < 0x0a }) != -1:
            glog.Infof("Response Body:\n%s", hex.Dump(body))

This corresponds with this snippet of the file.

[stevekuznetsov]

The sub-block identified is:

$ head -c 27704 vendor/k8s.io/kubernetes/pkg/client/restclient/request.go | tail -c +27685 > debug.go

// debug.go 
 { return r < 0x0a }

[fjl]

We have a similar issue in github.com/ethereum/go-ethereum/p2p. The statement that causes it also involves a function literal inside case.

# cover github.com/ethereum/go-ethereum/p2p
cover: internal error: block 17 overlaps block 19
    /Users/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:#6707,#6842 /Users/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:#6764,#6792
cover: internal error: block 23 overlaps block 25
    /Users/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:#6993,#7086 /Users/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:#7047,#7066

It still happens with go 1.7rc3.

[minux]

A smaller and standalone reproduction:

$ cat issue16540_test.go
package issue16540
import "testing"
func Test(t *testing.T) {
switch {
case 1 == func() int { return 1 }():
return
}
}
$ go tool cover -mode=set -var=XXXX issue16540_test.go > /dev/null
cover: internal error: block 1 overlaps block 2
issue16540_test.go:#73,#118 issue16540_test.go:#94,#106

The two overlapping ranges are:
case 1 == func() int { return 1 }(): return
And:
{ return 1 }

[gopherbot]

CL https://golang.org/cl/32612 mentions this issue.