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test/atomicload.go
45 строк
798 B
Keith Randall
cmd/compile: keep value use counts in SSA
17 мар 2016, 07:20
17 мар 2016, 07:20
56e0ecc
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// run // Copyright 2016 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. // Check that we do loads exactly once. The SSA backend // once tried to do the load in f twice, once sign extended // and once zero extended. This can cause problems in // racy code, particularly sync/mutex. package main func f(p *byte) bool { x := *p a := int64(int8(x)) b := int64(uint8(x)) return a == b } func main() { var x byte const N = 1000000 c := make(chan struct{}) go func() { for i := 0; i < N; i++ { x = 1 } c <- struct{}{} }() go func() { for i := 0; i < N; i++ { x = 2 } c <- struct{}{} }() for i := 0; i < N; i++ { if !f(&x) { panic("non-atomic load!") } } <-c <-c }