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cmd/compile: internal compiler error: esc return list involving constant groups and unsafe.Sizeof #20260

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josharian opened this issue May 5, 2017 · 2 comments
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cmd/compile: internal compiler error: esc return list involving constant groups and unsafe.Sizeof #20260

josharian opened this issue May 5, 2017 · 2 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Unplanned

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@josharian
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package p

import "unsafe"

const (
	a = unsafe.Sizeof(func() int {
		return 0
	}())
	b
)
$ go tool compile x.go 
x.go:7:3: internal compiler error: esc return list

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/Users/josh/go/tip/src/runtime/debug/stack.go:24 +0xa7
cmd/compile/internal/gc.Fatalf(0x179c214, 0xf, 0x0, 0x0, 0x0)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/subr.go:181 +0x230
cmd/compile/internal/gc.(*EscState).esc(0xc4200b8400, 0xc4202f7280, 0xc420316280)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:871 +0x127d
cmd/compile/internal/gc.(*EscState).esclist(0xc4200b8400, 0xc4202eff40, 0xc420316280)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:648 +0x6d
cmd/compile/internal/gc.(*EscState).escfunc(0xc4200b8400, 0xc420316280)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:589 +0x18c
cmd/compile/internal/gc.escAnalyze(0xc42000c5e0, 0x1, 0x1, 0xc42031e000)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:491 +0x566
cmd/compile/internal/gc.(*bottomUpVisitor).visit(0xc420333810, 0xc420316280, 0xc400000002)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:107 +0x25c
cmd/compile/internal/gc.visitBottomUp(0xc4202efd40, 0x4, 0x4, 0x17b2200)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:63 +0xeb
cmd/compile/internal/gc.escapes(0xc4202efd40, 0x4, 0x4)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/esc.go:187 +0x4b
cmd/compile/internal/gc.Main(0x17b2080)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/main.go:545 +0x2392
main.main()
	/Users/josh/go/tip/src/cmd/compile/main.go:49 +0x95

Found with go-fuzz. Low priority.
@josharian josharian added this to the Unplanned milestone May 5, 2017
@josharian josharian mentioned this issue May 5, 2017
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@josharian
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Per #20262 and #12946, the bug here is that escape analysis is looking inside the function at all. The fix is probably to nil out the body of the function once typechecking has decided that we're working with unsafe.Sizeof and has determined the type of the return value.

@ALTree ALTree added the NeedsFix The path to resolution is known, but the work has not been done. label Sep 22, 2018
@ALTree
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ALTree commented Jul 1, 2019

I can't reproduce this on tip (to be 1.13), so it's possible that this was fixed by the recent escape analysis rewrite. Optimistically closing.

@ALTree ALTree closed this as completed Jul 1, 2019
@golang golang locked and limited conversation to collaborators Jun 30, 2020
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@josharian @ALTree @gopherbot