C++模板：为什么不调用专用函数？

模板函数作为一般和特殊情况存在：

#include <string>
#include <iostream>
using namespace std;

// General case
template<typename X> void whichOneIsLarger(X a, X b) {
    (a > b) ? cout << "x [" << a << "] is larger than y [" << b << "]" : cout << "y [" << b << "] is larger than x [" << a << "]" << endl;
}

// Specialization
template<> void whichOneIsLarger<string>(string a, string b) {
    (a.size() > b.size()) ? cout << "x [" << a << "] is longer than y [" << b << "]" : cout << "y [" << b << "] is longer than x [" << a << "]" << endl;
}

使用字符串调用它时，我希望两个调用都使用特化，为什么不是这样？

int main()
{
    string hallo = "hallo"; string world = "world";

    whichOneIsLarger(hallo, world);         // <-- Calls specialization
    whichOneIsLarger("hallo", "world");     // <-- Calls general case
}

回答

whichOneIsLarger(std::string("hallo"), std::string("world"));

using namespace std::string_literals;
whichOneIsLarger("hallo"s, "world"s); 

template<> void whichOneIsLarger<const char*>(const char* a, const char* b)