How to find length of sub-array

[subith86]

Here is my piece of code:

int b[2][2] =
    {
        {4,6},
        {-3,0}
    };
    int b_length = (sizeof b)/sizeof(int);

    int *sub_b = b[1];

b_length will have the length of 2-D array b (4, in this case).
now sub_b is the sub-array of b at row 1, which is {-3,0}
Is there any way to find the length of sub_b other than the below technique.

int sub_length = (sizeof b[1])/sizeof(int);