debug/dwarf: incorrect runtime.newproc DIE in .zdebug_info

[jschwinger233]

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

$ go version
go version go1.18.3 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN="/home/gray//bin"
GOCACHE="/home/gray/.cache/go-build"
GOENV="/home/gray/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/gray/pkg/mod"
GONOPROXY="git.insea.io"
GONOSUMDB="git.insea.io"
GOOS="linux"
GOPATH="/home/gray/"
GOPRIVATE="git.insea.io"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.3"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/gray/src/proving_grounds/go_hello_world/go.mod"
GOWORK=""
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-build2957214737=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Build a hello world:

package main

import "fmt"

func main() {
    fmt.Println("hello world")
}

Then check the runtime.newproc entry in .zdebug_info

$ objdump -Wi ./go_hello_world | grep 'runtime.newproc$' -A2
    <4196c>   DW_AT_name        : runtime.newproc
    <4197c>   DW_AT_low_pc      : 0x43a9a0
    <41984>   DW_AT_high_pc     : 0x43aa19
--
    <524a7>   DW_AT_name        : runtime.newproc
    <524b7>   DW_AT_low_pc      : 0x45cea0
    <524bf>   DW_AT_high_pc     : 0x45cecf

There are 2 different DIE for runtime.newproc, but only the first one is correct.

The second entry is actually for runtime.newproc.abi0, and we can tell it from the .symtab, but the dwarf emitter made mistakes:

$ nm ./go_hello_world | grep runtime.newproc
000000000043a9a0 T runtime.newproc
000000000043aaa0 T runtime.newproc1
000000000045cea0 T runtime.newproc.abi0
000000000043aa20 T runtime.newproc.func1
000000000054ef1c B runtime.newprocs

What did you expect to see?

I expected to see the only one entry for runtime.newproc.

What did you see instead?

I saw 2 different entries for runtime.newproc, in which one entry should have been runtime.newproc.abi0.

[mknyszek]

CC @golang/compiler

[cherrymui]

runtime.newproc.abi0 is a wrapper of runtime.newproc, and it immediately calls the latter. runtime.newproc.abi0 is the symbol name but user friendly name is the demangled runtime.newproc.

cc @thanm @aclements . Did we intentionally use the demangled name for DWARF?