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Currently, we handle "x op= y" by rewriting as "x = x op y", while ensuring that any calls or receive operations in 'x' are only evaluated once. Notably, pointer indirection, indexing operations, etc. are left alone as it's typically safe to re-evaluate those. However, those operations were interleaved with evaluating 'y', which could include function calls that might cause re-evaluation to yield different memory addresses. As a fix, simply ensure that we order side-effecting operations in 'y' before either evaluation of 'x'. Fixes #21687. Change-Id: Ib14e77760fda9c828e394e8e362dc9e5319a84b2 Reviewed-on: https://go-review.googlesource.com/60091 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
69 lines
940 B
Go
69 lines
940 B
Go
// run
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// Copyright 2017 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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// Issue 21687: cmd/compile evaluates x twice in "x op= y", which was
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// detectable if evaluating y affects x.
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package main
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func ptrs() (int, int) {
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one := 1
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two := 2
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x := &one
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*x += func() int {
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x = &two
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return 0
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}()
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return one, two
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}
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func slices() (int, int) {
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one := []int{1}
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two := []int{2}
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x := one
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x[0] += func() int {
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x = two
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return 0
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}()
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return one[0], two[0]
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}
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func maps() (int, int) {
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one := map[int]int{0: 1}
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two := map[int]int{0: 2}
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x := one
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x[0] += func() int {
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x = two
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return 0
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}()
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return one[0], two[0]
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}
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var tests = [...]func() (int, int){
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ptrs,
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slices,
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maps,
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}
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func main() {
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bad := 0
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for i, f := range tests {
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if a, b := f(); a+b != 3 {
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println(i, a, b)
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bad++
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}
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}
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if bad != 0 {
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panic(bad)
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}
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}
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