c - two arguments of arry and read the columns -

i have simple tab:

int rows = atoi(argv[1]); int tab[rows][2];

and i'm forwarding func by:

myfunc(tab); void myfunc(int (*tab)[2]);

how can read number of rows? still try about:

int readrowinmyfunc = sizeof(tab)/(sizeof(int **));

but doesn't work.

sizeof(tab) = rows * 2 * sizeof(int)

rows = sizeof(tab) / (2*sizeof(int))

note bad idea create array on stack dynamic size. if run program argv[1] = 100000000000000000000?

GHI