返回初始化列表机制 [英] returning initializer list mechanism

问题描述

涉及什么机制，如果当返回类型时，可以从初始化列表构造，我不指定我返回的类型，如：

What mechanism is involved, if when returning types, that are constructible from initializer lists, I don't specify the type I am returning, as in:

std::array<int, 3> make_array()
{
  return { 1, 2, 3 };
}

而不是

std::array<int, 3> make_array()
{
  return std::array<int, 3>{ 1, 2, 3 };
}

是否有任何性能损失，如果我返回初始化列表，类型？我实际上返回一个数组，转换为 std :: array ？

Are there any performance penalties involved, if I return the initializer list without specifying a type? Am I actually returning an array, that is converted into a std::array?

推荐答案

不涉及性能损失。返回值的构造等同于

There are no performance penalties involved. The return value is constructed equivalent to

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

甚至没有单个副本或移动 std :: array 涉及的实例。

There is not even a single copy or move of an std::array instance involved.

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