test20.c: In function 'func2':
test20.c:16:15: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 100;
               ^
test20.c:16:15: warning: Using variable 'ptr3' without checking for null pointer
test20.c: In function 'func4':
test20.c:31:14: warning: Useless variable check 'ptr1'. It already was checked before
     else if (!ptr1 && ptr2)
              ^
test20.c: In function 'func6':
test20.c:52:15: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 100;
               ^
test20.c:52:15: warning: Using variable 'ptr3' without checking for null pointer
test20.c: In function 'func7':
test20.c:66:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 100;
               ^
test20.c:66:15: warning: Using variable 'ptr1' without checking for null pointer
test20.c:67:15: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 200;
               ^
test20.c:67:15: warning: Using variable 'ptr3' without checking for null pointer
test20.c: In function 'func8':
test20.c:81:15: warning: Using variable 'ptr1' without checking for null pointer
     ptr1->val = 100;
               ^
test20.c:81:15: warning: Using variable 'ptr1' without checking for null pointer
test20.c:82:15: warning: Using variable 'ptr3' without checking for null pointer
     ptr3->val = 200;
               ^
test20.c:82:15: warning: Using variable 'ptr3' without checking for null pointer