c# - 没有 "Unassigned Local Variable"错误？

Question

为什么获取变量的地址可以消除“使用未分配的局部变量”错误？

(为什么一开始不初始化就可以取到地址？)

static unsafe void Main()
{
    int x;
    int* p = &x;  //No error?!
    x += 2;       //No error?!
}

Answer 1

C# 语言规范，第 18.5.4 节:

The & operator does not require its argument to be definitely assigned, but following an & operation, the variable to which the operator is applied is considered definitely assigned in the execution path in which the operation occurs. It is the responsibility of the programmer to ensure that correct initialization of the variable actually does take place in this situation.
...
The rules of definite assignment for the & operator exist such that redundant initialization of local variables can be avoided. For example, many external APIs take a pointer to a structure which is filled in by the API. Calls to such APIs typically pass the address of a local struct variable, and without the rule, redundant initialization of the struct variable would be required.