runtime: tracebacks don't print function arguments for inlined functions

[rockmenjack]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.11 linux/amd64

Does this issue reproduce with the latest release?

yes

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/rockmen1/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/rockmen1/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build729838165=/tmp/go-build -gno-record-gcc-switches"

What did you expect to see?

run this in go playground, which runs version 1.10.3

panic: oops

goroutine 1 [running]:
main.test(0xc420045f68, 0x1, 0x1, 0x469f51, 0x7, 0x2710, 0xc420078000)  <- parameters trace
        /tmp/test.go:4 +0x39
main.main()
        /tmp/test.go:8 +0x73

What did you see instead?

panic: oops

goroutine 1 [running]:
main.test(...)                                           <- gone 
        /tmp/test.go:4
main.main()
        /tmp/test.go:8 +0x39

[agnivade]

/cc @ianlancetaylor @aclements

[thanm]

This is presumably because main.test is now being inlined. If you add something that prevents the inline, you'll see the params in the panic trace. E.g.

func test(a []string, b string, c int) int {
	defer func() { fmt.Printf("whee!\n") }()
	panic("oops")
}

[rockmenjack]

Any rules for function inlining? Assuming complex function won't be inlined?

[cznic]

//go:noinline <#12312> --

…

-j

[randall77]

I'm going to punt this to unplanned. It would be nice to fill in the ... for inlined functions, but I don't think anyone has a good idea of how to do that.
(It would require DWARF-like annotations in the runtime data structures to reconstruct the args from registers or locals and/or report them as unavailable.)