这是一个创建于 2213 天前的主题，其中的信息可能已经有所发展或是发生改变。
package main
import (
"fmt"
"log"
"net/http"
"os"
"time"
)
var Q []string
func main() {
go func() {
time.Sleep(1 * time.Second)
for {
test()
}
}()
Q = append(Q, "233")
Q = append(Q, "233")
Q = append(Q, "233")
time.Sleep(3 * time.Second)
Q = append(Q, "233")
Q = append(Q, "233")
Q = append(Q, "233")
Q = append(Q, "233")
Q = append(Q, "233")
time.Sleep(3 * time.Second)
Q = append(Q, "233")
time.Sleep(3 * time.Second)
Q = append(Q, "233")
http.HandleFunc("/", handle)
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Println("http port has been used.")
os.Exit(-1)
}
}
func handle(w http.ResponseWriter, r *http.Request) {
defer r.Body.Close()
_ = r.ParseForm()
_, _ = fmt.Fprint(w, "hello")
}
func test() {
file := queueOut()
if file != "" {
log.Println(file)
}
}
func queueOut() string {
res := Q[0]
if len(Q) == 1 {
Q[0] = ""
return res
}
Q = Q[1:]
return res
}
我觉得我这样写没错啊. 但是运行的时候有几率出现
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1058fe5]
goroutine 19 [running]:
fmt.(*buffer).WriteString(...)
/opt/local/lib/go/src/fmt/print.go:82
fmt.(*fmt).padString(0xc000114040, 0x0, 0x3)
/opt/local/lib/go/src/fmt/format.go:110 +0x9d
fmt.(*fmt).fmtS(0xc000114040, 0x0, 0x3)
/opt/local/lib/go/src/fmt/format.go:328 +0x61
fmt.(*pp).fmtString(0xc000114000, 0x0, 0x3, 0x76)
/opt/local/lib/go/src/fmt/print.go:437 +0x122
fmt.(*pp).printArg(0xc000114000, 0x1247a20, 0xc000010050, 0x76)
/opt/local/lib/go/src/fmt/print.go:671 +0x878
fmt.(*pp).doPrintln(0xc000114000, 0xc0000cffa8, 0x1, 0x1)
/opt/local/lib/go/src/fmt/print.go:1146 +0xb1
fmt.Sprintln(0xc0000cffa8, 0x1, 0x1, 0x1247a20, 0x1)
/opt/local/lib/go/src/fmt/print.go:271 +0x52
log.Println(0xc0000cffa8, 0x1, 0x1)
/opt/local/lib/go/src/log/log.go:301 +0x3f
main.test()
/Users/licsber/go/src/test/main.go:52 +0xd7
main.main.func1()
/Users/licsber/go/src/test/main.go:17 +0x2f
created by main.main
/Users/licsber/go/src/test/main.go:14 +0x39
Process finished with exit code 2
小白表示无法理解 这个问题是几率出现. 每次运行不一定都有
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1
mlkr 2018-12-07 21:16:27 +08:00
要加锁吧
|
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2
AlphaTr 2018-12-07 21:18:59 +08:00
slice 的线程安全问题，加锁？
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4
mlkr 2018-12-07 21:26:07 +08:00  1
package main
import ( "fmt" "log" "net/http" "os" "sync" "time" ) var Q []string var lock sync.RWMutex func main() { go func() { time.Sleep(1 * time.Second) for { test() } }() Q = append(Q, "233") Q = append(Q, "233") Q = append(Q, "233") time.Sleep(3 * time.Second) Q = append(Q, "233") Q = append(Q, "233") Q = append(Q, "233") Q = append(Q, "233") Q = append(Q, "233") time.Sleep(3 * time.Second) Q = append(Q, "233") time.Sleep(3 * time.Second) Q = append(Q, "233") http.HandleFunc("/", handle) err := http.ListenAndServe(":8080", nil) if err != nil { log.Println("http port has been used.") os.Exit(-1) } } func handle(w http.ResponseWriter, r *http.Request) { defer r.Body.Close() _ = r.ParseForm() _, _ = fmt.Fprint(w, "hello") } func test() { file := queueOut() if file != "" { log.Println(file) } } func queueOut() string { // 加写锁 lock.Lock() res := Q[0] if len(Q) == 1 { Q[0] = "" return res } Q = Q[1:] lock.Unlock() return res } |
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5
littlewing 2018-12-07 21:29:03 +08:00
有 channel 不用非要用非线程安全的 slice
另外 slice 的 append 操作是会重新分配 slice 结构的，而且你的 slice 初始 len 为 0，每次扩容时存储数据的 array 也会重新分配，问题应该就出现在这里 |
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7
Licsber OP @littlewing channel 是啥.. 刚学 go 还没看到 我去看看 谢谢
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8
mritd 2018-12-07 21:37:36 +08:00 via iPhone
大哥你这个 ... channel 啊
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9
heimeil 2018-12-07 22:00:55 +08:00
Q = Q[1:]瞬间执行多次，这个并发直接把 Q 给 cut 没了，再访问 Q 的任意下标自然就崩了。
要非得用 slice 就别直接操作 slice，另外封装两个增删方法，加上锁。 |
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10
mlkr 2018-12-07 22:12:18 +08:00
@Licsber
func queueOut() string { res := Q[0] if len(Q) == 1 { Q[0] = "" return res } // 加写锁 lock.Lock() Q = Q[1:] lock.Unlock() return res } |
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11
AngryPanda 2018-12-07 22:14:49 +08:00 via Android 1
channel 没学等于没学 go
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14
Licsber OP @AngryPanda 刚看到 go routine , 感谢
现在接触的 go 给我一种我一直在处理错误(err)的错觉 |
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