在c++中将2维数组值初始化为“0”时出错，给出了垃圾值

#include <iostream>

const int ROWS = 3;
const int COLS = 3;

int main() {
    int arr[ROWS][COLS] = {};  // 初始化为0

    // 输出初始化后的数组
    for (int i = 0; i < ROWS; i++) {
        for (int j = 0; j < COLS; j++) {
            std::cout << arr[i][j] << " ";
        }
        std::cout << std::endl;
    }

    return 0;
}

int arr[ROWS][COLS];
for (int i = 0; i < ROWS; i++) {
    for (int j = 0; j < COLS; j++) {
        arr[i][j] = 0;
    }
}