msvc编译器 c++类型对象作为返回值时为什么会进行多次拷贝构造？

先上代码

class Base {
public:
	int val = -1;
	Base() {}
	Base(int v) :val(v) {}
};

自定义的类型对象

using namespace std;
class Test {
public:
	Base* base;
	Test(const Test& other) {
		cout << "copy-constructor called : This=" << this << ",other=" << &other << endl;
		base = other.base;
	}
	Test(Test&& other) noexcept {
		cout << "rvalue copy-constructor called : This=" << this << ",other=" << &other << ",base->val=" << other.base->val << endl;
		base = other.base;
		other.base = nullptr;
	}
	explicit Test(Base* b) : base(b) {
		cout << "constructor called : This=" << this << ",base->val=" << base->val << endl;
	}
	~Test() {
		cout << "destructor called : This=" << this << endl;
		if (base != nullptr)delete base;
	}
};

测试函数

Test func() {
	int val = 2;
	return val == 1 ? Test(new Base(1)) :
		val == 2 ? Test(new Base(2)) :
		val == 3 ? Test(new Base(3)) : Test(new Base(0));
}

int main()
{
	func();
}

运行结果

constructor called : This=00F6F58C,base->val=2
rvalue copy-constructor called : This=00F6F5A4,other=00F6F58C,base->val=2
rvalue copy-constructor called : This=00F6F6D0,other=00F6F5A4,base->val=2
destructor called : This=00F6F5A4
destructor called : This=00F6F58C
destructor called : This=00F6F6D0

为什么调用了两次右值参数的拷贝构造函数？

编译器是msvc2019 用gcc测试则不会发生此问题

估计是编译器的原因。我运行你的代码，GCC一次都没有调用右值拷贝构造函数。我本来认为是调用了一次，GCC优化掉了