test6.c: In function 'void func1(int*)':
test6.c:12:13: warning: Using variable without check for NULL
     *a = 100;
             ^
test6.c: In function 'void func5(int*)':
test6.c:45:13: warning: Using variable without check for NULL
     *a = 600;
             ^
test6.c: In function 'void func7(int*)':
test6.c:70:16: warning: Using variable without check for NULL
     *aptr = 800;
                ^