null pointer dereferencing: check that its a pointer that is dereferenced to avoid false positives when using classes that behave almost like pointers (#295)

src/checkother.cpp

@@ -964,7 +964,19 @@ void CheckOther::nullPointer()
             if (tok2->varId() == varid)
             {
                 if (tok2->next()->str() == "." || Token::Match(tok2->next(), "= %varid% .", varid))
-                    nullPointerError(tok2);
+                {
+                    // Is this variable a pointer?
+                    const Token *tok3 = Token::findmatch(_tokenizer->tokens(), "%type% * %varid% [;)]", varid);
+                    if (!tok3)
+                        break;
+
+                    if (!tok3->previous() ||
+                        Token::Match(tok3->previous(), "[({};]") ||
+                        tok3->previous()->isName())
+                    {
+                        nullPointerError(tok2);
+                    }
+                }
                 break;
             }
 

test/testother.cpp

@@ -59,6 +59,7 @@ private:
         TEST_CASE(varScope2);
 
         TEST_CASE(nullpointer1);
+        TEST_CASE(nullpointer2);
     }
 
     void check(const char code[])
@@ -411,6 +412,18 @@ private:
                          "}\n");
         ASSERT_EQUALS(std::string("[test.cpp:4]: (error) Possible null pointer dereference\n"), errout.str());
     }
+
+    void nullpointer2()
+    {
+        // Null pointer dereference can only happen with pointers
+        checkNullPointer("void foo()\n"
+                         "{\n"
+                         "    Fred fred;\n"
+                         "    while (fred);\n"
+                         "    fred.hello();\n"
+                         "}\n");
+        ASSERT_EQUALS(std::string(""), errout.str());
+    }
 };
 
 REGISTER_TEST(TestOther)