C++ - 未初始化向量的值<int>

问题描述

我从 这个问题 global/static uninitialized int 的值将为 0. this 表示对于向量，将调用对象类型的默认构造函数.

I understand from the answer to this question that values of global/static uninitialized int will be 0. The answer to this one says that for vectors, the default constructor for the object type will be called.

我无法弄清楚 - 当我有 vector 时会发生什么v(10) 在本地函数中.int 的默认构造函数是什么?如果我有 vector 怎么办?v(10) 全局声明?

I am unable to figure out - what happens when I have vector<int> v(10) in a local function. What is the default constructor for int? What if I have vector<int> v(10) declared globally?

我看到的是 vector本地函数中的 v(10) 导致变量为 0 - 但我不确定这是因为我的编译器还是固定的预期行为.

What I am seeing is that vector<int> v(10) in a local function is resulting in variables being 0 - but I am not sure if that is just because of my compiler or is the fixed expected behaviour.

推荐答案

零初始化在标准中被指定为内置类型的默认零初始化/值初始化，主要是为了在模板使用中支持这种类型的情况.

The zero initialization is specified in the standard as default zero initialization/value initialization for builtin types, primarily to support just this type of case in template use.

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请注意，此行为与诸如 int x; 之类的局部变量不同，后者会使值未初始化(如在继承行为的 C 语言中).

Note that this behavior is different from a local variable such as int x; which leaves the value uninitialized (as in the C language that behavior is inherited from).

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