英文:
How to prevent deadlock when change map data
问题
我尝试编写一个验证数据的函数。请看下面的代码：
func Create(name, email, password, local string, termOf bool) map[string]string {
wait := new(sync.WaitGroup)
mutex := new(sync.Mutex)
errMsg := make(map[string]string)
if !termOf {
mutex.Lock()
errMsg["termOf"] = translate(local, "text06")
mutex.Unlock()
}
wait.Add(1)
go func() {
err := ValidateName(name, local)
mutex.Lock()
errMsg["name"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Add(1)
go func() {
err := ValidateEmail(email, local)
mutex.Lock()
errMsg["email"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Add(1)
go func() {
err := ValidatePassword(password, local)
mutex.Lock()
errMsg["password"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Wait()
// 如果出现错误
if len(errMsg) > 0 {
return errMsg
}
return nil
}
正如你在这里看到的，我使用了三个 goroutine，在 goroutine 中我锁定它以更改 errMsg 变量的 map 类型。当我运行该函数时，我得到了编译器错误：
runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x14 pc=0x44206a]
但是当我在 goroutine 中删除所有的 errMsg 插入时，函数就可以正常工作。我不知道我做错了什么原因。
英文:
I try to write a function that validate data. Look at the following code:
func Create(name, email, password, local string, termOf bool) map[string]string {
wait := new(sync.WaitGroup)
mutex := new(sync.Mutex)
errMsg := make(map[string]string)
if !termOf {
mutex.Lock()
errMsg["termOf"] = translate(local, "text06")
mutex.Unlock()
}
wait.Add(1)
go func() {
err := ValidateName(name, local)
mutex.Lock()
errMsg["name"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Add(1)
go func() {
err := ValidateEmail(email, local)
mutex.Lock()
errMsg["email"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Add(1)
go func() {
err := ValidatePassword(password, local)
mutex.Lock()
errMsg["password"] = err.Error()
mutex.Unlock()
wait.Done()
}()
wait.Wait()
// If errors appear
if len(errMsg) > 0 {
return errMsg
}
return nil
}
As you can see here, I use three goroutines and in the goroutine I lock it to change errMsg variable map type. When I run the function, I've got compiler error
runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x14 pc=0x44206a]
But when I remove in the goroutine all errMsg inserts, then the function works. I do not know the reason what I do wrong.
答案1
得分: 3
从ValidateName()、ValidateEmail()或ValidatePassword()调用返回时，err可能是nil。
在将其添加到映射之前，应检查err != nil。
if err != nil {
mutex.Lock()
errMsg["xxx"] = err.Error()
mutex.Unlock()
}
换句话说，问题不在于映射errMsg，而在于您想要放入其中的值。
英文:
It is possible that err is nil when returning from ValidateName(), ValidateEmail() or ValidatePassword() calls.
You should check err != nil before adding it to the map.
if err != nil {
mutex.Lock()
errMsg["xxx"] = err.Error()
mutex.Unlock()
}
In other words, this isn't the map errMsg which is the issue, but the value you want to put in it.
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