[Interest] memory fragmentation?

[Lukas Geyer]

Am 22.08.2012 09:44, schrieb Graeme Gill:
> Lukas Geyer wrote:
>> The address space is expanded immediately but physical memory pages are
>> assigned at the moment the memory is accessed; either never, always or
>> at kernels discretion, depending on the implemented overcommit strategy [1].
>
> Right, but malloc will return NULL if the address space is not available.
> This is less likely on a 64 bit system, but quite possible on a 32 bit system.
> Whether you can actually use that memory is a different question,
> but it's certain that you can't use it if the address is NULL!

Of course, but one has to be aware that the nullptr validation serves a 
different purpose then (address space availability validation, not 
memory availability validation) and thus can be used as a fail condition 
only, because the success condition has (theoretically) no practical 
value, as you don't know wheter you can actually use the memory 
provided, or not.

int *value = new int;
if (value != nullptr)
     *value = 42; // Bang, you are dead.