Herb Sutter整过一个M & M rule (Mutex and mutable go together)

这个blog挺绕的
https://herbsutter.com/2013/05/24/gotw-6a-const-correctness-part-1-3/

https://herbsutter.com/2013/05/28/gotw-6b-solution-const-correctness-part-2/
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修改:z16166 FROM 221.218.160.*
FROM 221.218.160.*