Null references redux

[Walter Bright]

Nick Sabalausky wrote:

I agree with you that if the compiler can detect null dereferences at 
compile time, it should.


>> Also, by "safe" I presume you mean "memory safe" which means free of 
>> memory corruption. Null pointer exceptions are memory safe. A null pointer 
>> could be caused by memory corruption, but it cannot *cause* memory 
>> corruption.
> 
> No, he's using the real meaning of "safe", not the misleadingly-limited 
> "SafeD" version of "safe" (which I'm still convinced is going to get some 
> poor soul into serious trouble from mistakingly thinking their SafeD program 
> is much safer than it really is). Out here in reality, "safe" also means a 
> lack of ability to crash, or at least some level of protection against it. 

Memory safety is something that can be guaranteed (presuming the 
compiler is correctly implemented). There is no way to guarantee that a 
non-trivial program cannot crash. It's the old halting problem.

> You seem to be under the impression that nothing can be made uncrashable 
> without introducing the possibility of corrupted state. That's hogwash.

I read that statement several times and I still don't understand what it 
means.

BTW, hardware null pointer checking is a safety feature, just like array 
bounds checking is.