Note the need for the extern keyword2003 because otherwise a const array variable would have internallinkage.
因为记得文件范围内的函数与变量默认都是外部链接。
2
In the same vein, assert is also used to test the internal state of a function-such as private member variables, or variables with internallinkage used strictly within the file.
同理，断言也被用来测试函数的内部状态，比如说私有成员变量或者文件的内部变量(variables with inner - linkage used strictly within the file .)。
3
It is guaranteed that an unnamed space is unique for each translation unit. If you put local names in a unnamed namespace, you don't need to give them internallinkage by making them static.