隐式使用 initializer_list

Question

§[dcl.init.list] 8.5.4/2:

The template std::initializer_list is not predefined; if the header <initializer_list> is not included prior to a use of std::initializer_list — even an implicit use in which the type is not named (7.1.6.4) — the program is ill-formed.

这是否意味着这个程序格式错误？

#include <vector>
int main() {
    // uses vector::vector(initializer_list<T>, const Allocator&) constructor
    std::vector<int> v = {1, 2, 3};
}

Answer 1

你的程序不是ill-formed因为<vector>保证包含<initializer_list>（所有标准库容器也是如此）

§23.3.1 [sequences.general]

Header <vector> 剧情简介

#include <initializer_list>
...

搜索 #include <initializer_list> 的标准显示 header 与以下 headers

一起包含

<utility>
<string>
<array>
<deque>
<forward_list>
<list>
<vector>
<map>
<set>
<unordered_map>
<unordered_set>
<queue>
<stack>
<algorithm>
<random>
<valarray>
<regex>

隐式使用 initializer_list

Implicit use of initializer_list

c++

c++11

initializer-list