Mutithreading accessing one std::map , will cause unsafe behavior?
<p>If more than one thread access one map object, but, I can make sure any of these threads accessing will not have the same key, and the accessing is just like:</p>

<pre><code>//find value by key
//if find
// erase the object or change the value
//else
// add new object of the key
</code></pre>

<p>Will the operation cause synchronization problem？</p>
