Re: Integer subtype and NaN trick

[Coda Highland <chighland@...>]

On Sat, Jun 15, 2013 at 10:35 PM, Miles Bader <miles@gnu.org> wrote:
> Coda Highland <chighland@gmail.com> writes:
>> The problem is that on modern OSes, you can't assume that you can
>> fit a 64-bit pointer in 48 bits.
>
> My impression was that current implementations of the x86-64
> architecture only use 48 bits of addresses, requiring the upper 16
> bits to be identical.  Has this changed with very recent
> implementations?

Unless I'm wrong, ASLR isn't restricted to 48 bits. Virtual memory
allocation can use whatever addresses it wants.

>> This is (part of) why LuaJIT demands to use the low 2GB.
>
> Yeah the 2GB limitation is a huge lose... but that's obviously a lot
> more restrictive than necessary...

Well, there are ways around it in LuaJIT.

/s/ Adam