test16.c: In function 'func2':
test16.c:26:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 300;
         ^
test16.c: In function 'func3':
test16.c:31:21: warning: Using parameter 'ptr1' without checking for null pointer
     if (ptr1 || ptr1->val == 100)
                     ^
test16.c:36:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 200;
         ^
test16.c: In function 'func4':
test16.c:41:22: warning: Using parameter 'ptr1' without checking for null pointer
     if (!ptr1 && ptr1->val == 100)
                      ^
test16.c:46:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 200;
         ^
test16.c: In function 'func6':
test16.c:67:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 300;
         ^
test16.c:68:9: warning: Using parameter 'ptr2' without checking for null pointer
     ptr2->val = 400;
         ^