dhcpcd-discuss

On Fri, 19 Jan 2018 09:30:25 +0000
Roy Marples <roy@xxxxxxxxxxxx> wrote:

> Hi
> 
> On 18/01/2018 23:48, jobhunts02@xxxxxxx wrote:
> > I see that dhcpcd-7.0.0 uses ULL’s.  Can it be configured to run on a 32-bit system?  If so, how?  If not, what version of dhcpcd would I need to use?  I want support for IPv6.  
> 
> dhcpcd works fine on 32-bits.
> In fact my current main dev platform is NetBSD/i386 thanks to my 2yold 
> ripping the keys out of my x86_64 laptop.
> 
> How does this work? Well, modern C (as of C99 I think) says that the 
> dialect must support unsigned long long and how this works on the 
> hardware is up to the compiler. As you can't put a 64-bit number into a 
> 32-bit one, you need to use 2x 32-bit numbers. This isn't optimal in 
> terms of speed and size - ideally we keep things at or below 32-bits on 
> on a 32-bit platform, but frankly it's very convenient and an easier 
> code path to use 64-bits as they are available.

IIRC, the 32-bit Linux kernel has used 64-bit ints for a long time now in a lot of places. One such use is in filesystems in order to 'break' the 2GiB or 4GiB limits on file sizes.