# map 是线程安全的吗

map 不是线程安全的。

在查找、赋值、遍历、删除的过程中都会检测写标志，一旦发现写标志置位（等于1），则直接 panic。赋值和删除函数在检测完写标志是复位之后，先将写标志位置位，才会进行之后的操作。

检测写标志：

```go
if h.flags&hashWriting == 0 {
        throw("concurrent map writes")
    }
```

设置写标志：

```go
h.flags |= hashWriting
```


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