问题 

chan

怎么答 

chan

举例

1. 写未初始化的 chan
package main
// 写未初始化的chan
func main() {
 var c chan int
 c <- 1
}
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// 输出结果
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan send (nil chan)]:
main.main()
        /Users/admin18/go/src/repos/main.go:6 +0x36
复制代码
chan send (nil chan)
2. 写读未初始化的 chan
package main
import "fmt"
// 读未初始化的chan
func main() {
 var c chan int
 num, ok := <-c
 fmt.Printf("读chan的协程结束, num=%v, ok=%v\n", num, ok)
}
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// 输出结果
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive (nil chan)]:
main.main()
        /Users/admin18/go/src/repos/main.go:6 +0x46
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chan receive (nil chan)

多问一句 

chanchan

1. 对于写的情况

//在 src/runtime/chan.go中
func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
 if c == nil {
      // 不能阻塞，直接返回 false，表示未发送成功
      if !block {
        return false
      }
      gopark(nil, nil, waitReasonChanSendNilChan, traceEvGoStop, 2)
      throw("unreachable")
 }
  // 省略其他逻辑
}
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channilfalsechanchangopark(nil, nil, waitReasonChanSendNilChan, traceEvGoStop, 2)throw(s string)waitReasonChanSendNilChan"chan send (nil chan)"

2. 对于读的情况

//在 src/runtime/chan.go中
func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool) {
    //省略逻辑...
    if c == nil {
        if !block {
          return
        }
        gopark(nil, nil, waitReasonChanReceiveNilChan, traceEvGoStop, 2)
        throw("unreachable")
    }
    //省略逻辑...
} 
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channilfalsechanchangopark(nil, nil, waitReasonChanReceiveNilChan, traceEvGoStop, 2)throw(s string)waitReasonChanReceiveNilChan"chan receive (nil chan)"

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