为什么解除指向一个整数数组(在2d数组中)的指针返回(或衰减到)指

why and how does this decay happen where the array itself decays to first element of the 1d array?

C11：6.3.2.1 p(3)：

Except when it is the operand of the sizeof operator,the _Alignof operator ¹,the unary & operator,or is a string literal used to initialize an array,an expression that has type ‘‘array of type’’ is converted to an expression with type ‘‘pointer to type’’ that points
to the initial element of the array object and is not an lvalue.

简单;数组名称可以转换为指向其第一个元素的指针.

由于a是一个数组名称,它衰减到指向其第一个元素的指针,该元素是一维数组.它的类型是int(*)[2].由于(在衰减之后)是指向2 int数组的指针,* a是2个int的数组.由于这是一个数组类型,即* a是第一个1D数组的数组名,它衰减到指向数组对象的第一个元素(a [0] [0])的指针.所以,它的类型是int *.

is this true that b(declared above) and a[0] represent the same thing (both being 1d array and then decay to the pointer to first element in array of type (int*)?

是b和a [0]都是int *类型(衰变后).

1.阅读Keith Thompson的commat.另请阅读此answer,其中指出：C11标准的草案说数组有另一个例外,即当数组是新_Alignof运算符的操作数时.这是草案中的错误,在最终公布的C11标准中得到纠正; _Alignof只能应用于带括号的类型名称,而不能应用于表达式.