test20.c: In function 'func2':
test20.c:16:9: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 100;
         ^
test20.c: In function 'func6':
test20.c:52:9: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 100;
         ^
test20.c: In function 'func7':
test20.c:66:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 100;
         ^
test20.c:67:9: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 200;
         ^
test20.c: In function 'func8':
test20.c:81:9: warning: Using parameter 'ptr1' without checking for null pointer
     ptr1->val = 100;
         ^
test20.c:82:9: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 200;
         ^