| // $G $D/$F.go && $L $F.$A && ./$A.out |
| |
| // Copyright 2009 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. |
| |
| // This test is designed to flush out the case where two cases of a select can |
| // both end up running. See http://codereview.appspot.com/180068. |
| package main |
| |
| import ( |
| "flag" |
| "runtime" |
| ) |
| |
| var iterations *int = flag.Int("n", 100000, "number of iterations") |
| |
| // sender sends a counter to one of four different channels. If two |
| // cases both end up running in the same iteration, the same value will be sent |
| // to two different channels. |
| func sender(n int, c1, c2, c3, c4 chan<- int) { |
| defer close(c1) |
| defer close(c2) |
| |
| for i := 0; i < n; i++ { |
| select { |
| case c1 <- i: |
| case c2 <- i: |
| case c3 <- i: |
| case c4 <- i: |
| } |
| } |
| } |
| |
| // mux receives the values from sender and forwards them onto another channel. |
| // It would be simplier to just have sender's four cases all be the same |
| // channel, but this doesn't actually trigger the bug. |
| func mux(out chan<- int, in <-chan int) { |
| for { |
| v := <-in |
| if closed(in) { |
| close(out) |
| break |
| } |
| out <- v |
| } |
| } |
| |
| // recver gets a steam of values from the four mux's and checks for duplicates. |
| func recver(in <-chan int) { |
| seen := make(map[int]bool) |
| |
| for { |
| v := <-in |
| if closed(in) { |
| break |
| } |
| if _, ok := seen[v]; ok { |
| println("got duplicate value: ", v) |
| panic("fail") |
| } |
| seen[v] = true |
| } |
| } |
| |
| func main() { |
| runtime.GOMAXPROCS(2) |
| |
| c1 := make(chan int) |
| c2 := make(chan int) |
| c3 := make(chan int) |
| c4 := make(chan int) |
| cmux := make(chan int) |
| go sender(*iterations, c1, c2, c3, c4) |
| go mux(cmux, c1) |
| go mux(cmux, c2) |
| go mux(cmux, c3) |
| go mux(cmux, c4) |
| // We keep the recver because it might catch more bugs in the future. |
| // However, the result of the bug linked to at the top is that we'll |
| // end up panicing with: "throw: bad g->status in ready". |
| recver(cmux) |
| print("PASS\n") |
| } |