Passing a 2D array to function in C

问题

I have a 2d array (a chess board, but this is irrelevant to the problem) and I want to fill it using a function. The one I've written works fine, but after launching the program the console crashes. Any idea where the problem is? Thank you.

#include <stdio.h>
#include <stdlib.h>
void fill(int board[8][8]);
int main()
{   int board[8][8];
    fill(board);
    return 0;
}
void fill(int board[8][8])
{
    int a,b;

    for (a = 1; a <= 8; a++)
    {
        for (b = 1; b<= 8; b++)
        {
            if ((a==1) || (a==8)) board[a][b] = 7;
            if ((a==2) || (a==7)) board[a][b] = 9;
            if ((a==3) || (a==6)) board[a][b] = 11;
            if ((a==4) || (a==5)) board[a][b] = 13;
            printf("%d", board[a][b]);
        }
        printf("\n");
    }
}

回答1:

I see one problem: arrays are indexed from 0 in C. So the last case is board[7][7].

Accessing board[8][0] actually accesses the sub-array (the row) after the end of the actual array. It will compile but crash if the memory after the array isn't owned by your program (the famous segmentation fault).

I guess you should put a-1 and b-1 between the square brackets.

回答2:

Because you have access array out of bound. Array index start to zero in c.

回答3:

In your for-loop conditions:

for (b = 1; b<= 8; b++)

and

for (a = 1; a <= 8; a++)

Your for-loop runs till counter a and b is equal to 8. However, your array itself is deeclared as board[[8][8] which means that the counters for both the arrays should be from 0 to 7. Since your counter exceeds the last value of the array, it causes undefined behaviour, and leads to a segmentation fault.

You need to change your for-loop condition to:

for (b = 0; b < 8; b++)

and

for (a = 0; a < 8; a++)

EDIT: Judging from the rest of your code in the for-loop, changing the conditional statement of these loops will change the logic of your program. In that case, you could instead use board[a -1][b - 1] at all instances instead of board[a][b].

Using this method, the counter will only reach 8 - 1 = 7 for both counter cases, and will avoid a segmentation fault just like the first solution.

回答4:

As noted in several comments/answers, array index values range from 0 to n-1,

Change the following lines:

   for (a = 1; a <= 8; a++)
    {
        for (b = 1; b<= 8; b++)

To:

  for (a = 0; a <= 7; a++)
    {
        for (b = 0; b<= 7; b++)

Follow this with adjustments to the comparison statements in the inner loop accordingly.

来源：https://stackoverflow.com/questions/43018001/passing-a-2d-array-to-function-in-c

标签

multidimensional-array