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cmd/compile: := assignment in for loop statement throws internal compiler error #20840

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iamsamwood opened this issue Jun 28, 2017 · 1 comment

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commented Jun 28, 2017

Please answer these questions before submitting your issue. Thanks!

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

package main

import "fmt"

func main() {
	for ; false; j := 1 {
		fmt.Printf("%d", j)
	}
}

https://play.golang.org/p/n2qRCxIsaa

What did you expect to see?

A more descriptive compiler error.

What did you see instead?

tmp/sandbox205983736/main.go:5: internal compiler error: Value live at entry. It shouldn't be. func main, node j, value v52

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/usr/local/go/src/runtime/debug/stack.go:24 +0x79
cmd/compile/internal/gc.Fatalf(0xacd433, 0x40, 0xc420333200, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/subr.go:167 +0x226
cmd/compile/internal/gc.(*ssaExport).Fatalf(0xdcb195, 0x5, 0xacd433, 0x40, 0xc420333200, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:4979 +0x5d
cmd/compile/internal/ssa.(*Config).Fatalf(0xc42034a000, 0xc400000005, 0xacd433, 0x40, 0xc420333200, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/ssa/config.go:343 +0x6e
cmd/compile/internal/gc.(*state).Fatalf(0xc42031c1e0, 0xacd433, 0x40, 0xc420333200, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:286 +0x83
cmd/compile/internal/gc.(*simplePhiState).insertPhis(0xc4203454b0)
	/usr/local/go/src/cmd/compile/internal/gc/phi.go:458 +0x2c5
cmd/compile/internal/gc.(*state).insertPhis(0xc42031c1e0)
	/usr/local/go/src/cmd/compile/internal/gc/phi.go:33 +0x172
cmd/compile/internal/gc.buildssa(0xc42032fa70, 0x0)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:174 +0x8ee
cmd/compile/internal/gc.compile(0xc42032fa70)
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:362 +0x204
cmd/compile/internal/gc.funccompile(0xc42032fa70)
	/usr/local/go/src/cmd/compile/internal/gc/dcl.go:1292 +0xdc
cmd/compile/internal/gc.Main()
	/usr/local/go/src/cmd/compile/internal/gc/main.go:464 +0x1f08
main.main()
	/usr/local/go/src/cmd/compile/main.go:50 +0xfe

System details

tmp/sandbox269629440/main.go:5: internal compiler error: Value live at entry. It shouldn't be. func main, node j, value v49

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/usr/local/go/src/runtime/debug/stack.go:24 +0x79
cmd/compile/internal/gc.Fatalf(0xacd433, 0x40, 0xc420333140, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/subr.go:167 +0x226
cmd/compile/internal/gc.(*ssaExport).Fatalf(0xdcb195, 0x5, 0xacd433, 0x40, 0xc420333140, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:4979 +0x5d
cmd/compile/internal/ssa.(*Config).Fatalf(0xc42034a000, 0xc400000005, 0xacd433, 0x40, 0xc420333140, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/ssa/config.go:343 +0x6e
cmd/compile/internal/gc.(*state).Fatalf(0xc42031c1e0, 0xacd433, 0x40, 0xc420333140, 0x3, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:286 +0x83
cmd/compile/internal/gc.(*simplePhiState).insertPhis(0xc4203474b0)
	/usr/local/go/src/cmd/compile/internal/gc/phi.go:458 +0x2c5
cmd/compile/internal/gc.(*state).insertPhis(0xc42031c1e0)
	/usr/local/go/src/cmd/compile/internal/gc/phi.go:33 +0x172
cmd/compile/internal/gc.buildssa(0xc42032fa70, 0x0)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:174 +0x8ee
cmd/compile/internal/gc.compile(0xc42032fa70)
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:362 +0x204
cmd/compile/internal/gc.funccompile(0xc42032fa70)
	/usr/local/go/src/cmd/compile/internal/gc/dcl.go:1292 +0xdc
cmd/compile/internal/gc.Main()
	/usr/local/go/src/cmd/compile/internal/gc/main.go:464 +0x1f08
main.main()
	/usr/local/go/src/cmd/compile/main.go:50 +0xfe
@bradfitz

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commented Jun 28, 2017

This is fixed in Go 1.9. (tested with Go tip, a bit after Go 1.9beta2).

@bradfitz bradfitz closed this Jun 28, 2017

@cespare cespare changed the title := assignment in for loop statement throws internal compiler error cmd/compile: := assignment in for loop statement throws internal compiler error Jun 28, 2017

@golang golang locked and limited conversation to collaborators Jun 28, 2018

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