cmd/compile: internal compiler error: 'main': Value live at entry. It shouldn't be

[lurenjia528]

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

$ go version
go version go1.18 windows/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
set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\lurenjia\AppData\Local\go-build
set GOENV=C:\Users\lurenjia\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=D:\gopath\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=D:\gopath
set GOPRIVATE=
set GOPROXY=https://goproxy.io,direct
set GOROOT=D:\softwarelocation\go
set GOSUMDB=off
set GOTMPDIR=
set GOTOOLDIR=D:\softwarelocation\go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.18
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=D:\work\code\archer\archer-all\go.mod
set GOWORK=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\lurenjia\AppData\Local\Temp\go-build2952525131=/tmp/go-build -gno-record-gcc-switches

What did you do?

.\main.go:17:23: internal compiler error: 'main': Value live at entry. It shouldn't be. func main, node bbb..autotmp_0, value nil

Please file a bug report including a short program that triggers the error.
https://go.dev/issue/new

recurrent

 tree
.
├── aaa
│   └── main.go
└── bbb
    └── bbb.go

 # cat aaa/main.go 
package main

import (
        "archer-all/test/bbb"
)

func main() {
        bbb.InitOrUpdateTable()
}
# cat bbb/bbb.go 
package bbb

func InitOrUpdateTable() {
        println(T())
}

func T() (int, int) {
        return 1, 1
}

then

 go build aaa/main.go 
# command-line-arguments
aaa/main.go:12:23: internal compiler error: 'main': Value live at entry. It shouldn't be. func main, node bbb..autotmp_0, value nil

Please file a bug report including a short program that triggers the error.
https://go.dev/issue/new

but if modify bbb/bbb.go

package bbb

import "fmt"

func InitOrUpdateTable() {
	fmt.Println(1)
	println(T())
}

func T() (int, int) {
	return 1, 1
}

then

 # go run aaa/main.go 
1
1 1

What did you expect to see?

why is the println() error

What did you see instead?

[ianlancetaylor]

CC @randall77 @mdempsky

[mdempsky]

Playground link: https://go.dev/play/p/V1I_NzFDws5

[mdempsky]

I think the issue is we're missing export/import for n.Init for OPRINTLN, and other builtins that allow multiple arguments.

Good:

go/src/cmd/compile/internal/typecheck/iexport.go

Lines 2053 to 2063 in 89044b6

	case ir.OCALL, ir.OCALLFUNC, ir.OCALLMETH, ir.OCALLINTER, ir.OGETG:
	n := n.(*ir.CallExpr)
	if go117ExportTypes {
	w.op(n.Op())
	} else {
	w.op(ir.OCALL)
	}
	w.pos(n.Pos())
	w.stmtList(n.Init())
	w.expr(n.X)
	w.exprList(n.Args)

Bad:

go/src/cmd/compile/internal/typecheck/iexport.go

Lines 2036 to 2040 in 89044b6

	case ir.OAPPEND, ir.ODELETE, ir.ORECOVER, ir.OPRINT, ir.OPRINTN:
	n := n.(*ir.CallExpr)
	w.op(n.Op())
	w.pos(n.Pos())
	w.exprList(n.Args) // emits terminating OEND

Should be a straightforward fix (just matching changes to iexport.go and iimport.go, and a regress test case). I'll send a CL tomorrow, unless any contributors want to tackle it.

[gopherbot]

Change https://go.dev/cl/402854 mentions this issue: cmd/compile: fix missing export/import init nodes of builtins that allow multiple arguments

[mdempsky]

FWIW, I think the fix is small and could be easily backported, but I don't think it's necessary here.

It looks like the same issue existed back in Go 1.16, so it's not a recent regression. So there's probably no existing code running into this.

There's also two easy workarounds: (1) rewrite the code to manually spill the multi-value results to temporary variables (e.g., rewrite println(T()) to x, y := T(); println(x, y); or (2) mark the function as //go:noinline.

If anyone else thinks it deserves a backport, I encourage opening a backport issue and we can discuss further there. Thanks.