c++ - Is the GNU C++ library missing an unordered_map constructor?

Question

At least one C++ reference lists following constructor signature:

explicit unordered_map ( const allocator_type& alloc );

It seems that it is not included in /usr/include/c++/4.8.2/bits/unordered_map.h, though. At least I can't spot it and the compiler can't find it, as well.

Thus, my question: Is this constructor specified by the C++ standard? Is the GNU C++ library implementation of unordered_map violating the standard in that respect?

Answer 1

这个构造函数是由 C++ 标准指定的吗？

是的。

unordered_map 的 GNU C++ 库实现在这方面是否违反了标准？

是的。