[~]% cat a.c
#include <stdio.h>

void f(const char **s) {
	printf("%s\n", *s);
}

int main(int ac, char **av) {
	f(&av[0]);
	return 0;
}
[~]% gcc a.c && ./a.out
a.c: In function ‘main’:
a.c:8:2: warning: passing argument 1 of ‘f’ from incompatible pointer type
a.c:3:6: note: expected ‘const char **’ but argument is of type ‘char **’