Fixed 6634 (false positive: dereferencing null pointer in a sizeof operation)

lib/checknullpointer.cpp

@@ -312,6 +312,11 @@ void CheckNullPointer::nullPointerByDeRefAndChec()
     const bool printInconclusive = (_settings->inconclusive);
 
     for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
+        if (Token::Match(tok, "sizeof|decltype|typeid|typeof (")) {
+            tok = tok->next()->link();
+            continue;
+        }
+
         const Variable *var = tok->variable();
         if (!var || !var->isPointer() || tok == var->nameToken())
             continue;

test/testnullpointer.cpp

@@ -1737,6 +1737,13 @@ private:
               "    *p = 0;\n"
               "}");
         ASSERT_EQUALS("[test.cpp:3] -> [test.cpp:2]: (warning) Possible null pointer dereference: p - otherwise it is redundant to check it against null.\n", errout.str());
+
+        // sizeof
+        check("void f() {\n"
+              "  int *pointer = NULL;\n"
+              "  pointer = func(sizeof pointer[0]);\n"
+              "}", false, "test.cpp", false);
+        ASSERT_EQUALS("", errout.str());
     }
 
     // Test CheckNullPointer::nullConstantDereference