致命错误：unordered_map：没有这样的文件或目录（C++ 98，gcc 4.8.5，使用 CMAKE）

Question

gcc throws fatal error: unordered_map.h: No such file or directory on #include . I am using CMAKE, and gcc 4.8.5 compiler.

main:

#include "a.h"
...
void main() { ...}


a.h:
#include <unordered_map>

Answer 1

I wasn't able to cross reference, but it says that unordered_map was introduced in C++11.

Source: https://en.cppreference.com/w/cpp/container/unordered_map