David Hopwood <[EMAIL PROTECTED]> writes: > Matthias Blume wrote: >> I agree with Bob Harper about safety being language-specific and all >> that. But, with all due respect, I think his characterization of C is >> not accurate. > [...] >> AFAIC, C is C-unsafe by Bob's reasoning. > > Agreed. > >> Of course, C can be made safe quite easily: >> >> Define a state "undefined" that is considered "safe" and add a >> transition to "undefined" wherever necessary. > > I wouldn't say that was "quite easy" at all. > > C99 4 #2: > # If a "shall" or "shall not" requirement that appears outside of a constraint > # is violated, the behavior is undefined. Undefined behavior is otherwise > # indicated in this International Standard by the words "undefined behavior" > # *or by the omission of any explicit definition of behavior*. [...] > > In other words, to fix C to be a safe language (compatible with Standard C89 > or C99), you first have to resolve all the ambiguities in the standard where > the behaviour is *implicitly* undefined. There are a lot of them.
Yes, if you want to make the transition system completely explict, it won't be easy. I was thinking of a catch-all rule that says: transition to "undefined" unless specified otherwise. (Note that I am not actually advocating this approach to making a language "safe". For practical purposes, C is unsafe. (And so is C++.)) -- http://mail.python.org/mailman/listinfo/python-list
