How does D improve design practices over C++?

[Jarrett Billingsley]

On Wed, Oct 29, 2008 at 5:43 PM, Brad Roberts <braddr at puremagic.com> wrote:
> On Wed, 29 Oct 2008, Walter Bright wrote:
>
>> bearophile wrote:
>> > D1 is often safer than C and C++, but regarding safety there are
>> > several things that can improved still, often with no/little
>> > performance penalty (unsafe casting (automatic and manual), integral
>> > overflows, GC pointers Vs other pointers, nonnull types, named
>> > arguments, fallthrough switch cases, multi var assigns syntax
>> > missing, octal literals, bitwise operators as symbols instead English
>> > words, and many other smaller things I have listed in the past). You
>> > may want to tell them about the idea of SafeD too (javesque D).
>>
>> "Safety" in programming languages does not refer to program correctness, but
>> absence of bugs that could result in memory corruption. The agenda of SafeD is
>> to find the subset of D that can guarantee there is no memory corruption.
>>
>> Null pointer dereferencing, for example, is a program bug but is not a safety
>> issue because it cannot cause memory corruption.
>
> Actually, that's not true.  Dereferencing null _can_ corrupt memory.  As
> you well know, ptr[index] is just ptr + index.  Use a large and accurate
> enough index and you're out of that first page of memory and back into
> application memory space.  Find the address of a key stack variable and
> you've got room for all sorts of fun and mahem.
>
> These are the sorts of bugs in popular enough applications are the things
> that end up costing companies lots of money to emergency fix.  One of the
> few recent flash exploits were exactly this type of bug.
>
> Later,
> Brad
>

Interestingly, although null dereferences are unsafe, in a safe
language like SafeD it's not actually possible to do so.  There are no
pointers and arrays are bounds-checked.  So with the combination of
the typing system and the runtime checks, null can never actually be
dereferenced, so no special consideration has to be given to it.