null pointers: dereferencing a pointer and then checking if it's null (#49)

src/checkother.cpp

@@ -1029,7 +1029,7 @@ void CheckOther::nullPointer()
         }
     }
 
-    // Dereferencing a pointer and then checking if it's NULL..
+    // Dereferencing a struct pointer and then checking if it's NULL..
     for (const Token *tok1 = _tokenizer->tokens(); tok1; tok1 = tok1->next())
     {
         if (Token::Match(tok1, "[{};] %var% = %var% . %var%"))
@@ -1076,6 +1076,37 @@ void CheckOther::nullPointer()
             }
         }
     }
+
+    // Dereferencing a pointer and then checking if it's NULL..
+    for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
+    {
+        if (tok->str() == "if" && Token::Match(tok->previous(), "; if ( ! %var% )"))
+        {
+            const unsigned int varid(tok->tokAt(3)->varId());
+            if (varid == 0)
+                continue;
+
+            for (const Token *tok1 = tok->previous(); tok1; tok1 = tok1->previous())
+            {
+                if (tok1->varId() == varid)
+                {
+                    if (tok1->previous() && tok1->previous()->str() == "*")
+                    {
+                        nullPointerError(tok1);
+                        break;
+                    }
+                    else if (tok1->next() && tok1->next()->str() == "=")
+                    {
+                        break;
+                    }
+                }
+
+                else if (tok1->str() == "{" ||
+                         tok1->str() == "}")
+                    break;
+            }
+        }
+    }
 }
 
 

test/testother.cpp

@@ -59,6 +59,7 @@ private:
         TEST_CASE(nullpointer1);
         TEST_CASE(nullpointer2);
         TEST_CASE(nullpointer3);    // dereferencing struct and then checking if it's null
+        TEST_CASE(nullpointer4);
 
         TEST_CASE(oldStylePointerCast);
     }
@@ -410,6 +411,7 @@ private:
         Tokenizer tokenizer;
         std::istringstream istr(code);
         tokenizer.tokenize(istr, "test.cpp");
+        tokenizer.simplifyTokenList();
         tokenizer.setVarId();
 
         // Clear the error buffer..
@@ -508,6 +510,34 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    // Dereferencing a pointer and then checking if it is null
+    void nullpointer4()
+    {
+        // errors..
+        checkNullPointer("void foo(int *p)\n"
+                         "{\n"
+                         "    *p = 0;\n"
+                         "    if (!p)\n"
+                         "        ;\n"
+                         "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (error) Possible null pointer dereference\n", errout.str());
+
+        // no error
+        checkNullPointer("void foo(int *p)\n"
+                         "{\n"
+                         "    if (x)\n"
+                         "        p = 0;\n"
+                         "    else\n"
+                         "        *p = 0;\n"
+                         "    if (!p)\n"
+                         "        ;\n"
+                         "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
+
+
+
+
     void checkOldStylePointerCast(const char code[])
     {
         // Tokenize..