受限指针分配

Question

我有一个关于受限指针分配的问题。有关具体问题，请参阅代码中的 cmets。总的来说，我只是想知道限制是合法的（我已经阅读了标准，但仍有疑问:-(

int* Q = malloc(sizeof(int)*100);

{
    int* restrict R = Q;

    for(int j = 0; j < rand()%50; j++)
    {
        R[j] = rand();
    }

    Q = R; // The standard says assigning restricted child pointers to their parent is illegal.
           // If Q was a restricted pointer, is it correct to assume that this would be ILLEGAL?
           //
           // Since Q is unrestricted, is this a legal assignment?
           //
           // I guess I'm just wondering: 
           // What's the appropriate way to carry the value of R out of the block so
           // the code can continue where the above loop left off? 
}

{
    int* S = Q;   // unrestricted child pointers, continuing where R left off above
    int* T = Q+1; // S and T alias with these assignments

    for(int j = 0; j < 50; j++)
    {
        S[j] = T[j];
    }
}

感谢您的帮助！

Answer 1

由于被修改的对象（在第一行分配的数组）没有通过左值表达式修改，除了涉及受限指针，R 在声明 R 的那个块中，我认为你的代码示例定义明确。

如果Q 是受限指针，则示例将是未定义的。