检查指针是否指向给定数组 [英] Check if pointer points to given array

问题描述

因此，我有一个函数返回一个指向数组A中元素的指针.我有另一个函数将该指针作为参数.但是，我需要该函数能够处理可能将其传递给完全任意的指针的可能性.

So I have a function that returns a pointer to an element in an array A. I have another function that takes that pointer as a parameter. However, I need that function to be able to deal with the possibility that it may be passed a completely arbitrary pointer.

有没有一种方法可以检测指针是否指向结构内的某个位置?在这种情况下，我的数组A是什么?

Is there a way to be able to detect if a pointer points somewhere within a structure? In this case, my array A?

我见过关于C ++的类似问题，但关于C ++却没有.

I've seen similar questions regarding C++, but not with C.

推荐答案

唯一可移植的方法是对指针的所有可能有效值使用相等性测试.例如:

The only portable way is to use an equality test against all of the possible valid values for the pointer. For example:

int A[10];

bool points_to_A(int *ptr)
{
    for (int i = 0; i < 10; ++i)
        if ( ptr == &A[i] )
             return true;

    return false;
}

请注意，使用带有两个指针的关系运算符(例如<)或减法是未定义的行为，除非两个指针实际上确实指向同一数组的元素(或指向末尾的元素).

Note that using a relational operator (e.g. <), or subtraction, with two pointers is undefined behaviour unless the two pointers actually do point to elements of the same array (or one past the end).

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