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我正在尝试使用大括号初始化，使用多个指向派生类的共享指针来初始化指向基类的共享指针向量。代码（去除不相关的细节后）如下所示：

#include <vector>
#include <memory>
#include <iostream>

struct Base {
    Base(double xx) { x = xx; }
    virtual ~Base() {}
    double x;
};

struct Derived : public Base {
    Derived(double xx) : Base(xx) {}
};

int main(void) {
    std::vector<std::shared_ptr<Base>> v = {
        std::make_shared<Derived>(0.1),
        std::make_shared<Derived>(0.2),
        std::make_shared<Derived>(0.3)
    };
    std::vector<std::shared_ptr<Base>> v4(3);
    v4[0] = std::make_shared<Derived>(0.1);
    v4[1] = std::make_shared<Derived>(0.2);
    v4[2] = std::make_shared<Derived>(0.3);

    std::cout << "Without brace initialization: " << std::endl;
    for (auto x : v4) {
        std::cout << x->x << std::endl;
    }

    std::cout << "With brace initialization: " << std::endl;
    for (auto x : v) {
        std::cout << x->x << std::endl;
    }
}

当我在 Visual Studio 2013 下编译这段代码并在控制台中运行它时，结果是：

Without brace initialization:
0.1
0.2
0.3
With brace initialization:
7.52016e-310

然后程序崩溃。这是意料之中的，大括号初始化与 to 的隐式转换不兼容std::shared_ptr<Derived>，std::shared_ptr<Base>还是 Visual Studio 中的错误？大括号初始化是否在幕后做了一些魔术，阻止了共享指针转换（例如，引用指针）？

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