Fixed #2413 (fflush() with NULL argument is valid.)

lib/checknullpointer.cpp

@@ -86,7 +86,7 @@ void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token
             var.push_back(tok.tokAt(2));
         else if (value == 0 && Token::Match(&tok, "memchr|memcmp|memcpy|memmove|memset|strcpy|printf|sprintf|snprintf"))
             var.push_back(tok.tokAt(2));
-        else if (Token::simpleMatch(&tok, "fflush"))
+        else if (value != 0 && Token::simpleMatch(&tok, "fflush"))
             var.push_back(tok.tokAt(2));
     }
 

test/testnullpointer.cpp

@@ -821,6 +821,13 @@ private:
               "  strcpy(p, \"abcd\");\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:3]: (error) Null pointer dereference\n", errout.str());
+
+        // Ticket #2413 - it's ok to pass NULL to fflush
+        check("void foo() {\n"
+              "  fflush(NULL);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
     }
 
 };