Question

我偶尔会遇到“衰变”一词，例如当函数参数传入的数组衰减到指针时，或者当函数衰减到函数指针时。如果我正在编写一个c编译器，我会在哪里找到正式定义的“衰变”这个术语，并且会记录它出现的所有情况？

Answer 1

标准中的官方术语是“左值转换”。在当前版本的标准（C11）中，您可以在6.3.2.1 p3中找到它。

Answer 2

第二次谷歌搜索产生了这个：

The K&R method of reducing arrays to pointers
 ---------------------------------------------
 K&R tried to create a unified treatment of arrays and pointers, one that 
 would expose rather than hide the array equation in the compiler's code. 
 They found an elegant solution, albeit a bit complicated. The "ugly" 
 array equation is replaced in their formulation by four rules:

    1) An array of dimension N is a 1D array with
       elements that are arrays of dimension N-1.

    2) Pointer addition is defined by:

          ptr # n = ptr + n * size(type-pointed-into)

       "#" denotes here pointer addition to avoid 
       confusion with ordinary addition.
       The function "size()" returns object's sizes.

    3) The famous "decay convention": an array is 
       treated as a pointer that points to the 
       first element of the array.

       The decay convention shouldn't be applied
       more than once to the same object.

    4) Taking a subscript with value i is equivalent 
       to the operation: "pointer-add i and then 
       type-dereference the sum", i.e.

          xxx[i] = *(xxx # i)


        When rule #4 + rule #3 are applied recursively 
        (this is the case of a multi-dimensional array), 
        only the data type is dereferenced and not the 
        pointer's value, except on the last step.

Source

Answer 3

C标准是回答这些问题的唯一方法。

如果您想购买官方文档，则需要查找 ISO / IEC 9899：2011 。或者可能更喜欢1999年或1989年的旧标准。</ p>

或者，2011标准的最终草案可以在这里找到，并且应该足够接近： http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf

Answer 4

数组名称衰减表示其值被处理（=具有类型和值）作为指向其第一个元素的指针。请注意，数组名称并不总是衰减（例如，不作为sizeof运算符的操作数）。不完整的同义词可能被视为或被重写为或只是被用作。

在Ansi C中 - 定义了“衰变”的哪个位置，以及所有出现的案例都记录在案？

4 个答案: