Rare SIGSEGV in fillREFDeltaObjectContent

[vmarkovtsev]

I run the same code from src-d/hercules around 50 times and it works. On 51st, I get the following SIGSEGV:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x48 pc=0x621dce]
goroutine 1 [running]:
gopkg.in/src-d/go-git.v4/plumbing/format/packfile.(*Decoder).fillREFDeltaObjectContent(0xc4200109c0, 0x1574640, 0xc420c61200, 0xd769e2e5682e8a44, 0x72bec494cfa7b359, 0xbf527d77, 0x4098cc, 0xc420c33cbc, 0x541430c2)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/decoder.go:365 +0xee
gopkg.in/src-d/go-git.v4/plumbing/format/packfile.(*Decoder).decodeByHeader(0xc4200109c0, 0xc420c611c0, 0x15665c0, 0xc420072d90, 0xc420c71101, 0x14)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/decoder.go:288 +0x104
gopkg.in/src-d/go-git.v4/plumbing/format/packfile.(*Decoder).decodeIfSpecificType(0xc4200109c0, 0xc420c611c0, 0x0, 0x0, 0x0, 0x0)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/decoder.go:234 +0x306
gopkg.in/src-d/go-git.v4/plumbing/format/packfile.(*Decoder).DecodeObject(0xc4200109c0, 0x0, 0x0, 0x0, 0x0)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/decoder.go:219 +0xa7
gopkg.in/src-d/go-git.v4/storage/filesystem.(*packfileIter).Next(0xc4209cf9b0, 0xc420c33df8, 0x5a4281, 0xc420c577a0, 0x1574640)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/storage/filesystem/object.go:412 +0x41
gopkg.in/src-d/go-git.v4/plumbing/storer.(*MultiEncodedObjectIter).Next(0xc4209f5c00, 0xc420010600, 0x1574640, 0xc420c610c0, 0xc420c577a0)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/storer/object.go:205 +0x47
gopkg.in/src-d/go-git.v4/plumbing/object.(*storerCommitIter).Next(0xc4209f5c20, 0xc420c577a0, 0x0, 0x0)
	/home/travis/gopath/src/gopkg.in/src-d/go-git.v4/plumbing/object/commit.go:271 +0x37
gopkg.in/src-d/hercules%2ev3.init.11()
	/home/travis/gopath/src/gopkg.in/src-d/hercules.v3/pipeline_test.go:410 +0x56d
gopkg.in/src-d/hercules%2ev3.init()
	/home/travis/gopath/src/gopkg.in/src-d/hercules.v3/uast_test.go:302 +0x246
main.init()
	gopkg.in/src-d/hercules.v3/_test/_testmain.go:326 +0x5a
exit status 2

Link to Travis build

Again, the very same code worked OK in a different Travis node as well as worked OK before.

[vmarkovtsev]

I really hope that I will not have to heat my RAM chips... It happened again with the same stack trace. Unable to reproduce on my machine, only happens in Travis.

[vmarkovtsev]

I found the rule: it always crashes continuous-integration/travis-ci/pr and always passes continuous-integration/travis-ci/push

[vmarkovtsev]

I found the way to reproduce this:

git clone --depth=50 https://github.com/src-d/hercules.git src-d/hercules
cd src-d/hercules/
git fetch origin +refs/pull/21/merge
git checkout -qf FETCH_HEAD
go run reproduce.go

reproduce.go

package main

import (
  "io"
  "gopkg.in/src-d/go-git.v4"
)

func main() {
  repository, _ := git.PlainOpen(".")
  iter, _ := repository.CommitObjects()
  var err error
  for ; err != io.EOF; _, err = iter.Next() {
    if err != nil {
      panic(err)
    }
  }
}

[ajnavarro]

I think you are using an old go-git version. The lines on the panic do not correspond with the latest version on master: https://github.com/src-d/go-git/blob/master/plumbing/format/packfile/decoder.go .

Can you check the commit that are you using into the go-git package? thanks.

[vmarkovtsev]

Travis should fetch the latest commit corresponding to v4. Did we forget to update the tag?

[vmarkovtsev]

Is not reproduced on master. Waiting for the new release impatiently.