Confusing values when copying to another array

I am trying to copy values from one array to another in C. The original array is of type long int, and it is inputted to the function as *pixel_frequency. The array I want to copy to is temp, and it is a 2D array. However, when I try to copy the values, pixel_frequency is fine but temp gives strange results. Below is the relevant code and some sample output.

Code:

struct node *generate_nodes(long int *pixel_frequency) {
    int i;
    int temp[max_value + 1][2];

    for (i = 0; i < (max_value + 1); i++) {
        temp[i][0] = i;
        temp[i][1] = pixel_frequency[i];
        printf("Frequency for %d is %d\n", temp[i][0], temp[i][1]);
    }
...

Output (each frequency is supposed to be 256):

Frequency for 0 is 150160
Frequency for 1 is 256
Frequency for 2 is 256
Frequency for 3 is 256
Frequency for 4 is 255
...
Frequency for 254 is 892677956
Frequency for 255 is 1868789101

Below is an example version of code using your code snippet, take care of the return type and other things.

Instead of using a global variable for array size, you can pass it as a function argument so , it will be easy to identify the size of array you passed.

void generate_nodes(long int *pixel_frequency, size_t size) {
    size_t i;
    long int temp[size][2];
    for (i = 0; i < size; i++) {
        temp[i][0] = i;
        temp[i][1] = pixel_frequency[i];
        printf("Frequency for %ld is %ld\n", temp[i][0], temp[i][1]);
    }
}

If you have declared pixel_frequency as a local variable in a function and used the address of array after the variable went out of scope, will lead to undefined behaviour.

int main(void) {
    size_t max_len = 5000;
    size_t i;
    long int* pixel_frequency = malloc(max_len*sizeof(long int));

    for( i = 0; i < max_len; ++i) {
        pixel_frequency[i] = (i%256);
    }

    generate_nodes(pixel_frequency, max_len);
    return 0;
}