C++ Primer 4/e在Namespaces这个地方有一段说明：‘Prior to the introduction of namespaces in standard C++, programs had to declare names as static to make them local to a file. The use of file statics is inherited from C. In C, a global entity declared static is invisible outside the file in which it is declared.
警告
The use of file static declarations is deprecated by the C++ standard. A deprecated feature is one that may not be supported in future releases. File statics should be avoided and unnamed namespaces used instead.’
中文版的这样写：‘标准C++引入namespace之前，程式必须将某个名称宣告为static才能使它区域化（local to）于档案内。这种性质继承自C语言。在C语言中，宣告为static的global物体，在其所处档案之外是不可见的。
警告
C++不赞成使用file static变数宣告。这意味C++将来有可能不再支援此一特性。’
还好我static也很少用。