C++11:正确的 std::array 初始化? [英] C++11: Correct std::array initialization?

问题描述

如果我按如下方式初始化 std::array，编译器会警告我缺少大括号

If I initialize a std::array as follows, the compiler gives me a warning about missing braces

std::array<int, 4> a = {1, 2, 3, 4};

这解决了问题:

std::array<int, 4> a = {{1, 2, 3, 4}};

这是警告信息:

missing braces around initializer for 'std::array<int, 4u>::value_type [4] {aka int [4]}' [-Wmissing-braces]

这只是我的 gcc 版本中的一个错误，还是故意这样做的?如果是，为什么?

Is this just a bug in my version of gcc, or is it done intentionally? If so, why?

推荐答案

这是 std::array 的裸实现:

template<typename T, std::size_t N>
struct array {
    T __array_impl[N];
};

它是一个聚合结构，其唯一的数据成员是一个传统的数组，这样内部的 {} 用于初始化内部数组.

It's an aggregate struct whose only data member is a traditional array, such that the inner {} is used to initialize the inner array.

在聚合初始化的某些情况下允许大括号省略(但通常不推荐)，因此在这种情况下只能使用一个大括号.请参见此处:C++ 数组向量

Brace elision is allowed in certain cases with aggregate initialization (but usually not recommended) and so only one brace can be used in this case. See here: C++ vector of arrays

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