Only if you can be sure you have touched all the interesting portions of input-space. Ideally your tests are doing this, but wherever your tests miss aren't covered by valgrind or mudflap but are covered by a change of language. That's a part of what's meant by safe. It's not that it's impossible to write correct code in an unsafe language. It's that it's difficult to impossible to verify that you have written correct code. I'm very willing to include available tools in that calculation, but valgrind and mudflap (while tremendously useful) cannot give guarantees.