C++ 类为typename的模板变量

我正在学习C++14，在这方面我遇到了这个模板变量特性，我对此很感兴趣，我尝试用多个例子来理解模板变量。说

template <typename T>
T var;

var<int>;
var<float>;

---

此简单程序不会创建任何临时对象：

int main() {
  var<SomeClass>;
}

按这个顺序

#include <iostream>

struct noisy {
  noisy() { std::cout << __func__ << "()\n"; }
  ~noisy() { std::cout << __func__ << "()\n"; }
  noisy(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  noisy(noisy const&) { std::cout << __func__ << "(c&)\n"; }
  void operator=(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  void operator=(noisy const&) { std::cout << __func__ << "(c&)\n"; }
};

template<class T>
T var;

int main() {
    std::cout << "Start of main\n";
    {
        var<noisy> = noisy{};
        std::cout << "Body of main\n";
    }
    std::cout << "End of main\n";
}

---

此简单程序不会创建任何临时对象：

int main() {
  var<SomeClass>;
}

按这个顺序

#include <iostream>

struct noisy {
  noisy() { std::cout << __func__ << "()\n"; }
  ~noisy() { std::cout << __func__ << "()\n"; }
  noisy(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  noisy(noisy const&) { std::cout << __func__ << "(c&)\n"; }
  void operator=(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  void operator=(noisy const&) { std::cout << __func__ << "(c&)\n"; }
};

template<class T>
T var;

int main() {
    std::cout << "Start of main\n";
    {
        var<noisy> = noisy{};
        std::cout << "Body of main\n";
    }
    std::cout << "End of main\n";
}

---

1. <代码>变量本身并不创建临时对象。2.事实并非如此<代码>变量本身并不创建临时对象。2.没有。

int main() {
  var<SomeClass> = SomeClass{};
}

 SomeClass::SomeClass()
 SomeClass::SomeClass()
 SomeClass::operator=(SomeClass&&)
 SomeClass::~SomeClass()
 SomeClass::~SomeClass()

#include <iostream>

struct noisy {
  noisy() { std::cout << __func__ << "()\n"; }
  ~noisy() { std::cout << __func__ << "()\n"; }
  noisy(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  noisy(noisy const&) { std::cout << __func__ << "(c&)\n"; }
  void operator=(noisy&&) { std::cout << __func__ << "(&&)\n"; }
  void operator=(noisy const&) { std::cout << __func__ << "(c&)\n"; }
};

template<class T>
T var;

int main() {
    std::cout << "Start of main\n";
    {
        var<noisy> = noisy{};
        std::cout << "Body of main\n";
    }
    std::cout << "End of main\n";
}

noisy()
Start of main
noisy()
operator=(&&)
~noisy()
Body of main
End of main
~noisy()