c - 在 C 中，全局结构的成员是否默认初始化为零？

Question

C 中的全局或静态结构的成员是否保证自动初始化为零，与uninitialized global or static variables are 的方式相同？ ？

Answer 1

来自 C99 标准 6.7.8/10“初始化”:

If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static storage duration is not initialized explicitly, then:

— if it has pointer type, it is initialized to a null pointer;
— if it has arithmetic type, it is initialized to (positive or unsigned) zero;
— if it is an aggregate, every member is initialized (recursively) according to these rules;
— if it is a union, the first named member is initialized (recursively) according to these rules

由于全局和静态结构具有静态存储持续时间，所以答案是肯定的——它们是零初始化的(结构中的指针将被设置为 NULL 指针值，通常是零位，但严格来说不需要是)。

C++ 2003 标准有类似的要求(3.6.2“非局部对象的初始化”):

Objects with static storage duration (3.7.1) shall be zero-initialized (8.5) before any other initialization takes place.

在零初始化发生后的某个时间，构造函数将根据更复杂的规则调用(如果对象具有构造函数)，这些规则控制这些调用的时间和顺序。