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As an optimization, function literals capture variables by value when they're not assigned and their address has not been taken. Because result parameters are implicitly assigned through return statements (which do not otherwise set the "assigned" flag), result parameters are explicitly handled to always capture by reference. However, the logic was slightly mistaken because it was only checking if the variable in the immediately enclosing context was a return parameter, whereas in a multiply-nested function literal it would itself be another closure variable (PAUTOHEAP) rather than a return parameter (PPARAMOUT). The fix is to simply test the outermost variable, like the rest of the if statement's tests were already doing. Fixes #32175. Change-Id: Ibadde033ff89a1b47584b3f56c0014d8e5a74512 Reviewed-on: https://go-review.googlesource.com/c/go/+/178541 Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
23 lines
373 B
Go
23 lines
373 B
Go
// run
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// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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// This used to print 0, because x was incorrectly captured by value.
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func f() (x int) {
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defer func() func() {
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return func() {
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println(x)
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}
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}()()
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return 42
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}
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func main() {
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f()
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}
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