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author | Matthew Dempsky <mdempsky@google.com> | 2020-12-10 12:21:45 -0800 |
---|---|---|
committer | Matthew Dempsky <mdempsky@google.com> | 2020-12-11 22:02:02 +0000 |
commit | 14305527f686ced0de8d08b3a62bd96fe6359481 (patch) | |
tree | aa9684ae8b3a408e67e25c44e56f9d48e3d79fd6 | |
parent | 1341a3decd00d1106efaa73c5ff4ffcabc4e6afd (diff) | |
download | go-14305527f686ced0de8d08b3a62bd96fe6359481.tar.gz go-14305527f686ced0de8d08b3a62bd96fe6359481.zip |
cmd/compile: fix select statement evaluation order corner case
The Go spec requires that select case clauses be evaluated in order,
which is stricter than normal ordering semantics. cmd/compile handled
this correctly for send clauses, but was not correctly handling
receive clauses that involved bare variable references.
Discovered with @cuonglm.
Fixes #43111.
Change-Id: Iec93b6514dd771875b084ba49c15d7f4531b4a6f
Reviewed-on: https://go-review.googlesource.com/c/go/+/277132
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
-rw-r--r-- | src/cmd/compile/internal/gc/order.go | 2 | ||||
-rw-r--r-- | test/fixedbugs/issue43111.go | 70 |
2 files changed, 71 insertions, 1 deletions
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go index 863de5b6c7..30e1535c09 100644 --- a/src/cmd/compile/internal/gc/order.go +++ b/src/cmd/compile/internal/gc/order.go @@ -891,7 +891,7 @@ func (o *Order) stmt(n *Node) { // c is always evaluated; x and ok are only evaluated when assigned. r.Right.Left = o.expr(r.Right.Left, nil) - if r.Right.Left.Op != ONAME { + if !r.Right.Left.IsAutoTmp() { r.Right.Left = o.copyExpr(r.Right.Left, r.Right.Left.Type, false) } diff --git a/test/fixedbugs/issue43111.go b/test/fixedbugs/issue43111.go new file mode 100644 index 0000000000..76d7beb084 --- /dev/null +++ b/test/fixedbugs/issue43111.go @@ -0,0 +1,70 @@ +// run + +// Copyright 2020 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +var ch chan int +var x int + +func f() int { + close(ch) + ch = nil + return 0 +} + +func g() int { + ch = nil + x = 0 + return 0 +} + +func main() { + var nilch chan int + var v int + var ok bool + _, _ = v, ok + + ch = make(chan int) + select { + case <-ch: + case nilch <- f(): + } + + ch = make(chan int) + select { + case v = <-ch: + case nilch <- f(): + } + + ch = make(chan int) + select { + case v := <-ch: _ = v + case nilch <- f(): + } + + ch = make(chan int) + select { + case v, ok = <-ch: + case nilch <- f(): + } + + ch = make(chan int) + select { + case v, ok := <-ch: _, _ = v, ok + case nilch <- f(): + } + + ch1 := make(chan int, 1) + ch = ch1 + x = 42 + select { + case ch <- x: + case nilch <- g(): + } + if got := <-ch1; got != 42 { + panic(got) + } +} |