debug/gosym: Sym.PackageName provides the wrong result

[Zxilly]

Go version

go version go1.22.0 windows/amd64

Output of go env in your module/workspace:

set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\zxilly\AppData\Local\go-build
set GOENV=C:\Users\zxilly\AppData\Roaming\go\env
set GOEXE=
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\zxilly\go\pkg\mod
set GONOPROXY=1
set GONOSUMDB=
set GOOS=linux
set GOPATH=C:\Users\zxilly\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:/Program Files/Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLCHAIN=auto
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.22.0
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=E:\Temp\gotmp\go.mod
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-fPIC -m64 -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\zxilly\AppData\Local\Temp\go-build2223077610=/tmp/go-build -gno-record-gcc-switches

What did you do?

In some edge cases, Sym.PackageName will provide incorrect results.
I'm sorry I couldn't provide a minimally reproducible sample. But you can find a sample at https://github.com/ZNotify/server/releases/download/test/analysis-server-linux.

I use the follow code to identify the wrong output.

package main

import (
	"debug/elf"
	"debug/gosym"
	"fmt"
	"strings"
)

func main() {
	f, err := elf.Open("analysis-server-linux")
	if err != nil {
		panic(err)
	}
	// read pclntab
	pclntab, err := f.Section(".gopclntab").Data()
	if err != nil {
		panic(err)
	}

	var textStart uint64
	symbols, err := f.Symbols()
	if err != nil {
		panic(err)
	}
	for _, sym := range symbols {
		if sym.Name == "runtime.text" {
			textStart = sym.Value
			break
		}
	}
	if textStart == 0 {
		panic("runtime.text not found")
	}

	// create gosym.Table
	ltable := gosym.NewLineTable(pclntab, textStart)
	table,err := gosym.NewTable(nil, ltable)
	if err != nil {
		panic(err)
	}

	for _, fn := range table.Funcs {
		pkgName := fn.PackageName()
		if strings.Contains(pkgName, "*") {
			fmt.Printf("FnName: %s\nPackageGot:%s\n", fn.Name, fn.PackageName())
		}
	}
}

What did you see happen?

With the script above, I get the follow output

FnName: ariga.io/atlas/sql/sqlclient.(*Tx).database/sql.grabConn
PackageGot:ariga.io/atlas/sql/sqlclient.(*Tx).database/sql
FnName: ariga.io/atlas/sql/sqlclient.(*Tx).database/sql.txCtx
PackageGot:ariga.io/atlas/sql/sqlclient.(*Tx).database/sql
FnName: github.com/ZNotify/server/app/api/common.(*Context).github.com/gin-gonic/gin.reset
PackageGot:github.com/ZNotify/server/app/api/common.(*Context).github.com/gin-gonic/gin

What did you expect to see?

The correct package for these names should be

ariga.io/atlas/sql/sqlclient
ariga.io/atlas/sql/sqlclient
github.com/ZNotify/server/app/api/common

[Zxilly]

I also test it with some other popular golang project like k8s.

For https://github.com/Zxilly/go-testdata/releases/download/kube/kubelet-linux-1.22-amd64, we got

FnName: github.com/google/cel-go/parser/gen.(*CELLexer).github.com/antlr/antlr4/runtime/Go/antlr/v4.reset
PackageGot:github.com/google/cel-go/parser/gen.(*CELLexer).github.com/antlr/antlr4/runtime/Go/antlr/v4
FnName: github.com/google/cel-go/parser/gen.(*CELParser).github.com/antlr/antlr4/runtime/Go/antlr/v4.reset
PackageGot:github.com/google/cel-go/parser/gen.(*CELParser).github.com/antlr/antlr4/runtime/Go/antlr/v4
FnName: github.com/google/cel-go/parser.(*recoveryLimitErrorStrategy).github.com/antlr/antlr4/runtime/Go/antlr/v4.reset
PackageGot:github.com/google/cel-go/parser.(*recoveryLimitErrorStrategy).github.com/antlr/antlr4/runtime/Go/antlr/v4
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FieldOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FieldOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FieldOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FieldOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumValueOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumValueOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumValueOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumValueOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*EnumOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ExtensionRangeOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ExtensionRangeOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ExtensionRangeOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ExtensionRangeOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*OneofOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*OneofOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*OneofOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*OneofOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MessageOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MessageOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MessageOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MessageOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MethodOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MethodOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MethodOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*MethodOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ServiceOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ServiceOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ServiceOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*ServiceOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FileOptions).github.com/gogo/protobuf/proto.extensionsRead
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FileOptions).github.com/gogo/protobuf/proto
FnName: github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FileOptions).github.com/gogo/protobuf/proto.extensionsWrite
PackageGot:github.com/gogo/protobuf/protoc-gen-gogo/descriptor.(*FileOptions).github.com/gogo/protobuf/proto

I suspect that something triggers a special rule at link time that adds an extra module name to the embedded receiver for identification purposes, but I can't find the exact code that adds the corresponding package name to the receiver, so I can't confirm that this is the actual behaviour occurring, and therefore can't write a patch that fixes the bug.

I would appreciate any help from anyone familiar with the linker codebase.

[cherrymui]

It seems to me we now are adding package paths to some of the methods (maybe just unexported methods? embedded methods?), which is unexpected to me. I think it probably occurs in the compiler, not the linker.

[Zxilly]

I agree with you, funcnametab was created by compiler and linker can do nothing about it.

Another point of note is that when I look at the source file for these functions using table.PCToLine, it shows them as <autogenerated>, which suggests that they were inserted by the compiler and are not part of the code

[cherrymui]

Yeah, for embedded methods, the compiler creates wrapper methods on the outer type.

[Zxilly]

That's my guess too, but I can't reproduce it on a smaller example, do you have one of those?
I'm reading the code in gc about LSym, looking for specific rules for generating names.

[Zxilly]

If possible, I think we may need to change the rules for generating the symbol name.

Because things like this also happen with non-pointer receivers. For something like github.com/gogo/protobuf/protoc-gen-gogo/descriptor.FileOptions.github.com/gogo/protobuf/proto.extensionsWrite, there's no way to get the real package path since dot was allowed in the package path like gopkg.in/yaml.v3

[gopherbot]

Change https://go.dev/cl/572076 mentions this issue: cmd/compile/internal/ir: wrap the method package with parentheses

[cherrymui]

cc @golang/compiler

[mdempsky]

We package-prefix unexported promoted methods that were declared in another package. Something like this should produce prefixed method name:

package a
type T struct{}
func (T) m() {}

package b
import "path/to/a"
type U struct { a.T } // will produce a method named "path/to/b.U.path/to/a.m"

[Zxilly]

I was wondering if this issue might be fixed in go1.23

[Zxilly]

@mdempsky What do you think of https://go-review.googlesource.com/c/go/+/572076?