Question

我遇到了一些奇怪的C行为。我有一个数组（我标记为SHOULD_NOT_CHANGE）在一个看似无关的函数调用之后发生了变化。我的数组不是全局的，函数调用不包括特定的数组。如果有人能弄清楚发生了什么，我将非常感激。这是主要的：

Error in ans[!test & ok] <- rep(no, length.out = length(ans))[!test &  : 
  replacement has length zero
In addition: Warning message:
In rep(no, length.out = length(ans)) :
  'x' is NULL so the result will be NULL

这是罪魁祸首：

int main(){




    int generate4[16] = {0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    int propagate4[16] = {0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0};

    int SHOULD_NOT_CHANGE[4] = {0, 1, 0, 0};

    int carry_in16[4] = {1,2,1,1};
    int carry_in4[16] = {0};



    printf("\nShould be 1: %d", SHOULD_NOT_CHANGE[0]);
    printf("\nShould be 0: %d", SHOULD_NOT_CHANGE[1]);

    printf("\nSHOULD NOT CHANGE : ");
    print_binary_array(SHOULD_NOT_CHANGE, 4);



    // Here is where the problem is
    carry(propagate4, generate4, carry_in4, carry_in16, 64, 4);



    printf("\n\nShould be 0: %d", SHOULD_NOT_CHANGE[0]);
    printf("\nShould be 1: %d", SHOULD_NOT_CHANGE[1]);

    printf("\nSHOULD NOT CHANGE : ");
    print_binary_array(SHOULD_NOT_CHANGE, 4);

    return 0;
}

这是我的输出：

void carry(int* p, int* g, int* carry_in, int* group_carry, int size, int block)
{

for (int j = 0; j < block; j++){
    carry_in[j] = g[j]  +  p[j] * group_carry[j];

    for (int i = 1; i < block*4; i++){
        carry_in[4*j+i] = g[4*j+i]  +  p[4*j+i] * group_carry[j];
    }
}
}

Answer 1

您正在索引超过函数carry_in中carry的范围。 block为4，因此4*block为16.因此j从0到3，i从1到15运行。因此4*j+i可以是大到12 + 15 = 27，方式大于最大安全值15。

数组由不相关的函数更改

1 个答案: