Templates and std::numeric_limits

问题

I have a class called Atomic which is basically an _Atomic_word plus methods that call the gcc atomic builtins.

class Atomic{
    mutable volatile _Atomic_word value_;
public:
    Atomic(int value = 0): value_(value) {}
    **** blah blah ****
};

I would like std::numeric_limits<Atomic> to instantiate to std::numeric_limits<underlying integer type> (e.g. on my system _Atomic_word is just a typedef for int).

Is there a way to do this?

回答1:

std::numeric_limits<Atomic> will instantiate with Atomic as the type, you can't subvert that. However you could specialise std::numeric_limits for Atomic like this

template<>
class numeric_limits< Atomic > : public numeric_limits< Atomic::UnderlyingType >
{
};

where you obviously expose UnderlyingType as a type in Atomic.

来源：https://stackoverflow.com/questions/1615197/templates-and-stdnumeric-limits