Garbage Collection Pitfall in C++ but not in D?

[Alex Rønne Petersen]

On 06-07-2012 16:07, Denis Shelomovskij wrote:
> 06.07.2012 17:43, akaz пишет:
>> Hi,
>>
>> Reading about the C++11, I stumbled upon this:
>>
>> http://www2.research.att.com/~bs/C++0xFAQ.html#gc-abi
>>
>> Specifically (quote):
>>
>> int* p = new int;
>> p+=10;
>> // ... collector may run here ...
>> p-=10;
>> *p = 10; // can we be sure that the int is still there?
>>
>> How does the D garbage collector solves (answers) that?
>>
>> Thank you.
>
> If you are interested in D read this first:
> http://dlang.org/garbage.html
>
> You can find there e.g.:
>  > Do not add or subtract an offset to a pointer such that the result
> points outside of the bounds of the garbage collected object originally
> allocated.
>
> So `p+=10;` is already "undefined behavior".
>

I'll just add: Handling this case is basically impossible to do sanely. 
You can't really know what some pointer off the bounds of a managed 
memory region is based on. It could literally be based on any memory 
region in the entire program. You could do heuristics of course, but . . .

-- 
Alex Rønne Petersen
alex at lycus.org
http://lycus.org