test16.c: In function 'func2':
test16.c:26:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 300;
               ^
test16.c:26:15: warning: Using variable 'ptr1' without checking for null pointer
test16.c: In function 'func3':
test16.c:31:27: warning: Using variable 'ptr1' without checking for null pointer
     if (ptr1 || ptr1->val == 100)
                           ^
test16.c:36:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 200;
               ^
test16.c:36:15: warning: Using variable 'ptr1' without checking for null pointer
test16.c: In function 'func4':
test16.c:41:28: warning: Using variable 'ptr1' without checking for null pointer
     if (!ptr1 && ptr1->val == 100)
                            ^
test16.c:46:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 200;
               ^
test16.c:46:15: warning: Using variable 'ptr1' without checking for null pointer
test16.c: In function 'func6':
test16.c:67:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 300;
               ^
test16.c:67:15: warning: Using variable 'ptr1' without checking for null pointer
test16.c:68:15: warning: Using variable 'ptr2' without checking for null pointer
     ptr2->val = 400;
               ^
test16.c:68:15: warning: Using variable 'ptr2' without checking for null pointer