internal/coverage/decodemeta: mishandled function literal flag in covdata read #57942
Description
What version of Go are you using (go version)?
$ go version go version devel go1.21-46d19b3ac9 Thu Jan 19 10:19:48 2023 -0500 linux/amd64
Does this issue reproduce with the latest release?
Only on tip / go 1.20
What operating system and processor architecture are you using (go env)?
linux/amd64
What did you do?
Build this program with "-cover" and run to collect coverage profile.
https://go.dev/play/p/Gs7UJrWz86r?v=gotip
E.g.
$ go build -o prog.exe -cover prog.go
$ mkdir /tmp/covdata
$ GOCOVERDIR=/tmp/covdata ./prog.exe
$ go tool covdata func -i=tmp/covdata
...
What did you expect to see?
Coverage profile includes "main".
What did you see instead?
Coverage profile is missing "main":
$ go tool covdata func -i=/tmp/covdata
/tmp/prog.go:5: *Atyp.Set 100.0%
/tmp/prog.go:9: Atyp.Get 100.0%
total (statements) 100.0%
$
What's happening here is that there is a coding error in the handling of the function literal flag in the meta-data decoder., this code here:
lit := d.r.ReadULEB128()
if lit != 0 {
f.Lit = true
}
is written incorrectly. The update to f.Lit should be unconditional (since we can't make any assumptions about the state of the FuncDesc passed in). If clients always pass in a zero FuncDesc everything will appear to work ok, but if not, the state of the "Lit" field will be whatever it was set to on the last go around.