没有“未分配的本地变量”错误？

Question

Why does taking the address of a variable eliminate the "Use of unassigned local variable" error?

(Why can we take the address without initialization in the first place?)

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

Answer 1

C# Language spec, section 18.5.4:

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.

Answer 2

我想因为，一旦你指向变量，编译器就无法分析是否通过该指针赋值，因此它被排除在明确的赋值分析之外。