c++里的各类初始化

c++中存在的各类初始化

总结一下c++中存在的各类初始化问题, 傻逼c++居然有8种初始化的方式。

1. Default-initialization: zero-initialization
2. Zero-initialization: value-initialization, non-local initialization, constant-initialization
3. Value-initialization: aggregate-initialization, list-initialization, default-initialization, zero-initialization, copy-initialization
4. Aggregate-initialization: list-initialization, copy-initialization, direct-initialization
5. List-initialization: direct-list-initialization, copy-list-initialization, aggregate-initialization, copy-initialization, direct-initialization
6. Direct-initialization: list-initialization, aggregate-initialization, value-initialization, copy-initialization
7. Copy-initialization: list-initialization, aggregate-initialization, direct-initialization
8. Constant-initialization: default-initialization
9. Reference initialization: list-initialization, copy-initialization, direct-initialization

• 默认初始化
  • 有构造就走构造
  • 没构造就随便来了，编译器合成
• 值初始化
  • 稍微要看编译器版本，一般{}和()都是初始化成零值
  • 如果是合成的构造函数，有些编译器也会表现出默认初始化行为

看完感受就两点

第一点，避免默认初始化， 第二点，尽量不要用引用的直接初始化延长生命周期，但比较尴尬的是这种操作只能发生一次，引用的传递不会延长生命周期，不要赌编译器行为。

#include <iostream>

int& fun() {
    int a = 66;
    return a;
}


int main() {
    auto b = fun();
}

像上面这种就活不过func call

REF

1. C++的各种初始化方式
2. When and how variables are initialized? Part 1
3. When and how variables are initialized? Part 2
4. When and how variables are initialized? - Part 3
5. When and how variables are initialized? - Part 4