Fixed #485 (detect when code is checking for null after dereferencing)

src/checkother.cpp

@@ -1024,6 +1024,32 @@ void CheckOther::nullPointer()
             tok2 = tok2->next();
         }
     }
+
+    // Dereferencing a pointer and then checking if it's NULL..
+    for (const Token *tok1 = _tokenizer->tokens(); tok1; tok1 = tok1->next())
+    {
+        if (Token::Match(tok1, "%var% . %var%"))
+        {
+            const unsigned int varid1(tok1->varId());
+            unsigned int indentlevel2 = 0;
+            for (const Token *tok2 = tok1->tokAt(3); tok2; tok2 = tok2->next())
+            {
+                if (tok2->str() == "{")
+                    ++indentlevel2;
+                else if (tok2->str() == "}")
+                {
+                    if (indentlevel2 == 0)
+                        break;
+                    --indentlevel2;
+                }
+                else if (tok2->str() == "if")
+                {
+                    if (Token::Match(tok2, "if ( !| %varid% )", varid1))
+                        nullPointerError(tok1);
+                }
+            }
+        }
+    }
 }
 
 

test/testother.cpp

@@ -58,6 +58,8 @@ private:
 
         TEST_CASE(nullpointer1);
         TEST_CASE(nullpointer2);
+        TEST_CASE(nullpointer3);
+        TEST_CASE(nullpointer4);
 
         TEST_CASE(oldStylePointerCast);
     }
@@ -444,6 +446,28 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void nullpointer3()
+    {
+        checkNullPointer("void foo(struct ABC *abc)\n"
+                         "{\n"
+                         "    int *a = abc->a;\n"
+                         "    if (!abc)\n"
+                         "        ;\n"
+                         "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (error) Possible null pointer dereference\n", errout.str());
+    }
+
+    void nullpointer4()
+    {
+        checkNullPointer("void foo(struct ABC *abc)\n"
+                         "{\n"
+                         "    int *a = abc->a;\n"
+                         "    if (abc)\n"
+                         "        ;\n"
+                         "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (error) Possible null pointer dereference\n", errout.str());
+    }
+
     void checkOldStylePointerCast(const char code[])
     {
         // Tokenize..