cmd/cover: go test -cover and go tool cover -func don't give the same results

[dlespiau]

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

go version go1.8 linux/amd64

What did you do?

I used the github.com/dlespiau/x86db package for the example below, but the same issue can be reproduced on other packages I have around and so assuming it's a general problem:

$ go test -coverprofile=profile.cov
PASS
coverage: 26.3% of statements

Whereas:

$ go tool cover -func=profile.cov | tail -1
total:							(statements)		26.1%

Not that I've noticed larger differences, up to 1% on other packages.

What did you expect to see?

I expect to see the same coverage number.

What did you see instead?

Two different coverage percentages.

[gopherbot]

CL https://golang.org/cl/44337 mentions this issue.

[JayNakrani]

Found the issue.

cmd/cover/func.go initializes total to 1 for each function. Whereas testing/cover.go only does it once. So if your code has lots of functions with total==0, then discrepancy is going to be high.

http://golang.org/cl/44337 should fix that.