2n-1 recursive pyramid

/* required is a function star (int n) that outputs n lines following this pattern:
*
***
*****
*******
.. etc, no loops or secondary functions allowed
*/
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
void star(int rows)
{
    if (rows == 0) return;

    static int b =1;
    static char *stars;
    if (b)
    {
        b=0;
        stars = malloc(rows*rows+1);
        strcpy(stars, "*");
    }
    star(rows-1);
    printf("%s\n", stars);

    stars = strcat(stars, "**");
}
int main (void)
{
star(5);
return 0;
}