gcc Unix&Mac OS program (1. Warning)

int main (int arg, char *argv)
{
 int i;
}

terminal command: cc -Wall -o warning warning.m

warning.m:2: warning: second argument of ‘main’ should be ‘char **’
warning.m: In function ‘main’:
warning.m:3: warning: unused variable ‘i’
warning.m:4: warning: control reaches end of non-void function

/*
* cc - Wall -Wno-unused warning.m (turn that unused warning off)
*/

/*
* cc -Wunused warning.m (only see unused warning mistakes)
*/