Fixed #2689 (False positive: Possible null pointer dereference)

lib/checknullpointer.cpp

@@ -660,6 +660,14 @@ void CheckNullPointer::nullPointerByCheckAndDeRef()
                     if (indentlevel == 0)
                         break;
                     --indentlevel;
+
+                    if (null && indentlevel == 0)
+                    {
+                        // skip all "else" blocks because they are not executed in this execution path
+                        while (Token::simpleMatch(tok2, "} else {"))
+                            tok2 = tok2->tokAt(2)->link();
+                        null = false;
+                    }
                 }
 
                 if (Token::Match(tok2, "goto|return|continue|break|throw|if|switch"))

test/testnullpointer.cpp

@@ -1001,6 +1001,15 @@ private:
               "    wilma->Reload();\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("void test(int *i) {\n"
+              "  if(i == NULL) {\n"
+              "    int b = 1;\n"
+              "  } else {\n"
+              "    int b = *i;\n"
+              "  }\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     // Test CheckNullPointer::nullConstantDereference