CheckNullPointer: Fix FP when x is NULL and address is calculated with expression '&x->y.z[0]'

lib/checknullpointer.cpp

@@ -171,6 +171,13 @@ bool CheckNullPointer::isPointerDeRef(const Token *tok, bool &unknown)
     if (parent->str() == "[" && (!parent->astParent() || parent->astParent()->str() != "&"))
         return true;
 
+    // address of member variable / array element
+    const Token *parent2 = parent;
+    while (Token::Match(parent2, "[|."))
+        parent2 = parent2->astParent();
+    if (parent2 != parent && parent2 && parent2->str() == "&" && !parent2->astOperand2())
+        return false;
+
     // read/write member variable
     if (firstOperand && parent->str() == "." && (!parent->astParent() || parent->astParent()->str() != "&")) {
         if (!parent->astParent() || parent->astParent()->str() != "(" || parent->astParent() == tok->previous())

test/testnullpointer.cpp

@@ -60,6 +60,7 @@ private:
         TEST_CASE(nullpointer25); // #5061
         TEST_CASE(nullpointer26); // #3589
         TEST_CASE(nullpointer27); // #6014
+        TEST_CASE(nullpointer_addressOf); // address of
         TEST_CASE(nullpointerSwitch); // #2626
         TEST_CASE(nullpointer_cast); // #4692
         TEST_CASE(nullpointer_castToVoid); // #3771
@@ -1335,6 +1336,20 @@ private:
                       "[test.cpp:3]: (error) Null pointer dereference\n", errout.str());
     }
 
+    void nullpointer_addressOf() { // address of
+        check("void f() {\n"
+              "  struct X *x = 0;\n"
+              "  if (addr == &x->y) {}\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+
+        check("void f() {\n"
+              "  struct X *x = 0;\n"
+              "  if (addr == &x->y.z[0]) {}\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void nullpointerSwitch() { // #2626
         check("char *f(int x) {\n"
               "    char *p = do_something();\n"