Emplace vs closures

[cym13 via Digitalmars-d]

On Monday, 19 September 2016 at 14:22:16 UTC, Steven 
Schveighoffer wrote:
> On 9/19/16 7:27 AM, Lodovico Giaretta wrote:
>
>> What I'd like to know: is this usage widespread? Should we 
>> forbid it for
>> the sake of security?
>
> No. There is no security concern here. You are dereferencing a 
> null pointer, which is perfectly safe.
>
> -Steve

I beg to defer, null pointer dereference is certainly not safe in 
the general case. In many cases it lead to code execution or 
privilege escalation. See for example CVE-2008-568 [1] for an 
example in kernel space or CVE-2009-0385 [2] in user space.

The idea is that you are really trying to call a function in a 
part of memory that is not mapped, but if you are able to map the 
zero page and control what function pointer is present there then 
it is exploitable. I'd like people to get away from the idea that 
null pointer dereference is safe, it's not. In most cases it's 
not exploitable but that's definitely not a safe spot.

That being said I don't think it should be the burden of the 
library or language to deal with this for the reasons you exposed.

[1] http://www.trapkit.de/advisories/TKADV2008-015.txt
[2] http://www.trapkit.de/advisories/TKADV2009-004.txt