dereferencing null

[Timon Gehr]

On 03/03/2012 09:00 PM, deadalnix wrote:
> Le 03/03/2012 20:06, Walter Bright a écrit :
>> On 3/3/2012 2:13 AM, bearophile wrote:
>>> Walter:
>>>
>>>> Adding in software checks for null pointers will dramatically slow
>>>> things
>>>> down.
>>>
>>> Define this use of "dramatically" in a more quantitative and objective
>>> way,
>>> please. Is Java "dramatically" slower than C++/D here?
>>
>> You can try it for yourself. Take some OOP code of yours, and insert a
>> null check in front of every dereference of the class handle.
>
> Why would you want to check every time ? You program will get a signal
> from the system if it try to deference a null pointer, so thing can be
> done in the signal handler, and no cost is involved.

The signal will likely be the same for the following two code snippets:

void main(){
     Object o;
     o.toString();
}

void main(){
     *cast(int*)0xDEADBEEF = 1337;
}


How to detect whether or not the access violation was actually caused by 
a null pointer?