I was also, in fact, referring to the bulk of legacy code bases that can't just be fully rewritten. Almost all good engineering is done incrementally, including the adoption of something like safe_c.h (I can hardly fathom the insanity of trying to migrate a million LOC+ of C to that library in a single go). I'm arguing that engineering effort would be better spent refactoring and rewriting the application in a fully safe language one small piece at a time.