在struct panics invalid memory address or nil pointer dereference
的字段上调用atomic.AddInt64,但不是当我们重新排列字段顺序时;为什么?atomic.AddInt64导致无效的内存地址或零指针取消引用
使用这种类型:
type CountHandler struct {
c *RequestContext
count int64
}
,并呼吁atomic.AddInt64(&countHandler.count, 1)
(场c
为零在这一点上)恐慌。但不是当我们将其改写为:
type CountHandler struct {
count int64
c *RequestContext
}
错误消失。
我想它应该是这样,因为Go以顺序方式将数据保存在内存中,并且达到nil
值打破了这个序列(字节);但我不知道为什么是这样,因为指针应该有固定的大小nil
或其他值。
这是围棋的x86 1.4.2在Windows &完整的错误信息是:
2015/02/23 12:56:44 http: panic serving [::1]:51886: runtime error: invalid memory address or nil pointer dereference
goroutine 5 [running]:
net/http.func·011()
c:/go/src/net/http/server.go:1130 +0xa8
sync/atomic.AddUint64(0x731144, 0x1, 0x0, 0x0, 0x263168)
c:/go/src/sync/atomic/asm_386.s:118 +0xc
main.(*CountHandler).ServeHTTP(0x731140, 0x263180, 0x122f6380, 0x122f62a0)
C:/Workshop/Devox/Workshop-Go/src/geoho/web/app/app.go:62 +0x42
github.com/julienschmidt/httprouter.func·001(0x263180, 0x122f6380, 0x122f62a0, 0x0, 0x0, 0x0)
C:/Workshop/Devox/Workshop-Go/src/github.com/julienschmidt/httprouter/router.go:232 +0x4c
github.com/julienschmidt/httprouter.(*Router).ServeHTTP(0x122d5d20, 0x263180, 0x122f6380, 0x122f62a0)
C:/Workshop/Devox/Workshop-Go/src/github.com/julienschmidt/httprouter/router.go:298 +0x141
net/http.serverHandler.ServeHTTP(0x122d2280, 0x263180, 0x122f6380, 0x122f62a0)
c:/go/src/net/http/server.go:1703 +0x145
net/http.(*conn).serve(0x122e01e0)
c:/go/src/net/http/server.go:1204 +0x9d8
created by net/http.(*Server).Serve
c:/go/src/net/http/server.go:1751 +0x2ce
整个源代码(此代码是错误的,我正要学习alice
):
package main
import (
"fmt"
"github.com/julienschmidt/httprouter"
"github.com/justinas/alice"
"net/http"
"os"
"sync/atomic"
)
// play with alice
func main() {
c1 := alice.New(Counter, Texter).Then(nil)
router := httprouter.New()
router.Handler("GET", "/", c1)
router.GET("/kill", kill)
http.ListenAndServe(":27007", router)
}
func kill(rw http.ResponseWriter, rq *http.Request, pl httprouter.Params) {
os.Exit(0)
}
var ch CountHandler
// constructors:
func Counter(h http.Handler) http.Handler {
return &ch
}
func Texter(h http.Handler) http.Handler {
var t TextHandler
switch x := h.(type) {
case *CountHandler:
t.c = x.c
t.text = fmt.Sprintf("called so far %d", atomic.LoadInt64(&x.count))
}
return &t
}
// handlers:
type RequestContext struct {
val int
}
type CountHandler struct {
c *RequestContext
count int64
}
func (c *CountHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
atomic.AddInt64(&c.count, 1)
}
type TextHandler struct {
c *RequestContext
text string
}
func (t *TextHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
rw.Write([]byte(t.text))
}
看起来像一个bug给我。我把你的代码和Linux上运行得很好。在操场上也一样。看到这个:http://play.golang.org/p/fDFaZPi3nf这个确切的代码崩溃在你的Windows机器上? – 2015-02-23 09:25:07
是的,它应该工作。请发布更多代码,例如你如何创建你的'countHandler'变量。请瞄准[MCVE](http://stackoverflow.com/help/mcve)。 – icza 2015-02-23 09:26:15
谢谢;我已经添加了代码。 – 2015-02-23 09:32:09