Unable to open coverage profile using go tool cover with go1.9.2

[pavlo-v-chernykh]

Hi Dmitry,

Thanks for a great tool.

I have faced with the next issue trying to inspect coverage profile gathered by go-fuzz.

go tool cover -html=coverprofile
cover: inconsistent NumStmt: changed from 0 to 1

Some go env stuff

GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.9.2/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.9.2/libexec/pkg/tool/darwin_amd64"

go-fuzz rev: 490b850

Snippet of cover profile that causes the issue:

fmt/format.go:0.0,1.1 0 0
fmt/format.go:0.0,1.1 1 0

There are a lot of similar lines in the cover profile with different files as well (from std lib and from a project).

I did some investigation and found the place in go tool cover sources:

https://github.com/golang/go/blob/f39050c8ebf894ccedc0b99de96f7412be97af89/src/cmd/cover/profile.go#L94-L119

Also, I think the place in go-fuzz that introduced that 0 statements is

go-fuzz/go-fuzz-build/cover.go

Line 223 in 720fd7c

return []ast.Stmt{f.newCounter(pos, blockEnd, 0)}

I would like to fix that issue but do not understand where is the actual problem.

[dvyukov]

Thanks for the report. I don't have time to look into this right now. Sorry.

[tmc]

for the curious reader, I found that in one particular sample I was able to just remove stdlib coverage information and was able to successfully generate an html report with go tool cover

Update: I still get this failure.

[tiziano88]

FWIW I am also running into this issue.

[Kubuxu]

I dug a bit into it, all the results in form of fmt/format.go:0.0,1.1 are from AST trees with Position of 0 which is NoPos (no positional information available).

Those coverage trackers are installed here:
https://github.com/dvyukov/go-fuzz/blob/master/go-fuzz-build/cover.go#L531
Although I am not sure why.

As a quick workaround sed -i '/0.0,1.1/d' coverprofile works.

[disconnect3d]

Hey,

an additional workaround can also be "trimming absolute paths" as listed in: https://github.com/genjidb/genji/blob/814e7f889a0200a39a3c5b1380e851e7c01a8e33/.github/workflows/test-fuzz.yaml#L101-L107

Funnily, the linked code links to @Kubuxu comment :D. 🤯