Getting error: "munmap_chunk(): invalid pointer" for the following code

compiled the following code snippet with command: gcc -g -std=c99 src.c

src.c:

#include <stdio.h>
#include <stdlib.h>

void fill(int* arr, int len, int val) {
    for (int i = 0; i < len; ++i) arr[i] = val;
}

int main()
{
    printf("Hello World\n");
    int *p1, *p2;
    int *arr1 = malloc (sizeof(int) * 10);
    int *arr2 = malloc (sizeof(int) * 10);
    printf("BEFORE======================\narr1=%p, arr2=%p\n", arr1,arr2);
    fill(arr1, 10, 17);
    fill(arr2, 10, 23);
    p1 = &arr1[9];
    p2 = &arr2[9];
    printf("values at addresses %p, %p are respectively: %d, %d\n", p1, p2, *p1, *p2);
    arr1 = realloc(arr1, 200);
    arr2 = realloc(arr2, 200);
    printf("AFTER======================\narr1=%p, arr2=%p\n", arr1,arr2);
    fill(arr1, 200, 239);
    fill(arr2, 200, 347);
    printf("values at addresses %p, %p are respectively: %d, %d\n", p1, p2, *p1, *p2);
    p1 = &arr1[99];
    p2 = &arr2[99];
    printf("values at addresses %p, %p are respectively: %d, %d\n", p1, p2, *p1, *p2);
    free(arr2);
    free(arr1);
    
    return 0;
}

I was just trying out dynamic memory allocation. To my surprise the free call on arr2 is crashing. From the memory dump it seems the after reallocation, the arrays are overlapping, which I am not sure why.

The 2nd parameter of realloc is the size in bytes.

Therefore in these lines:

arr1 = realloc(arr1, 200);
arr2 = realloc(arr2, 200);

You allocate both arr1 and arr2 with 200 bytes, not int elements.

To fix it change it to:

arr1 = realloc(arr1, sizeof(int) * 200);
arr2 = realloc(arr2, sizeof(int) * 200);

A second issue (as @stark commented) is that in the first instance of this line (right after filling the arrays):

printf("values at addresses %p, %p are respectively: %d, %d\n", p1, p2, *p1, *p2);

p1 and p2 still point to the arrays before reallocation. They are therefore invalid, and derefrencing them causes undefined-behavior.
(The second instance of this line is OK, because p1 and p2 are assigned with the new arrays addresses).