Commit 9d23975d authored by Bryan C. Mills's avatar Bryan C. Mills

cmd/go/internal/modload: ensure that __debug_modinfo__ is not discarded during linking

Fixes #28753
Updates #29628

Change-Id: I4a561be7d491a0d088e656b00151ae1bdbd16a84
Reviewed-on: https://go-review.googlesource.com/c/158357
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: default avatarBrad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: default avatarRuss Cox <rsc@golang.org>
parent 193c16a3
......@@ -252,10 +252,19 @@ func findModule(target, path string) module.Version {
func ModInfoProg(info string) []byte {
// Inject a variable with the debug information as runtime/debug.modinfo,
// but compile it in package main so that it is specific to the binary.
// No need to populate it in an init func; it will still work with go:linkname.
//
// The variable must be a literal so that it will have the correct value
// before the initializer for package main runs.
//
// We also want the value to be present even if runtime/debug.modinfo is
// otherwise unused in the rest of the program. Reading it in an init function
// suffices for now.
return []byte(fmt.Sprintf(`package main
import _ "unsafe"
//go:linkname __debug_modinfo__ runtime/debug.modinfo
var __debug_modinfo__ = %q
var keepalive_modinfo = __debug_modinfo__
func init() { keepalive_modinfo = __debug_modinfo__ }
`, string(infoStart)+info+string(infoEnd)))
}
......@@ -7,34 +7,83 @@ cd x
go mod edit -require=rsc.io/quote@v1.5.2
go mod edit -replace=rsc.io/quote@v1.5.2=rsc.io/quote@v1.0.0
go run main.go
stderr 'Hello, world.'
# Build a binary and ensure that it can output its own debug info.
# The debug info should be accessible before main starts (golang.org/issue/29628).
go build
exec ./x$GOEXE
stderr 'mod\s+x\s+\(devel\)'
stderr 'dep\s+rsc.io/quote\s+v1.5.2\s+'
stderr '=>\s+rsc.io/quote\s+v1.0.0\s+h1:'
stderr 'Hello, world.'
[short] skip
# Build a binary that accesses its debug info by reading the binary directly
# (rather than through debug.ReadBuildInfo).
# The debug info should still be present (golang.org/issue/28753).
cd unused
go build
exec ./unused$GOEXE
-- x/go.mod --
module x
-- x/lib/lib.go --
// Package lib accesses runtime/debug.modinfo before package main's init
// functions have run.
package lib
import "runtime/debug"
func init() {
m, ok := debug.ReadBuildInfo()
if !ok {
panic("failed debug.ReadBuildInfo")
}
println("mod", m.Main.Path, m.Main.Version)
for _, d := range m.Deps {
println("dep", d.Path, d.Version, d.Sum)
if r := d.Replace; r != nil {
println("=>", r.Path, r.Version, r.Sum)
}
}
}
-- x/main.go --
package main
import "runtime/debug"
import "rsc.io/quote"
import (
"rsc.io/quote"
_ "x/lib"
)
func main() {
println(quote.Hello())
m, ok := debug.ReadBuildInfo()
if !ok {
panic("failed debug.ReadBuildInfo")
}
println("mod", m.Main.Path, m.Main.Version)
for _, d := range m.Deps {
println("dep", d.Path, d.Version, d.Sum)
if r := d.Replace; r != nil {
println("=>", r.Path, r.Version, r.Sum)
}
}
println(quote.Hello())
}
-- x/unused/main.go --
// The unused binary does not access runtime/debug.modinfo.
package main
import (
"bytes"
"encoding/hex"
"io/ioutil"
"log"
"os"
_ "rsc.io/quote"
)
func main() {
b, err := ioutil.ReadFile(os.Args[0])
if err != nil {
log.Fatal(err)
}
infoStart, _ := hex.DecodeString("3077af0c9274080241e1c107e6d618e6")
if !bytes.Contains(b, infoStart) {
log.Fatal("infoStart not found in binary")
}
log.Println("ok")
}
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