64 bit DMD binary on the Mac

[Michel Fortin]

On 2011-06-29 20:55:43 -0400, Daniel Gibson <metalcaedes at gmail.com> said:

> Am 29.06.2011 22:01, schrieb Jacob Carlborg:
>> Yes exactly. Actually very few macs, what I've heard, run the kernel in
>> 64bit.
> 
> So is a 32bit kernel just default or can't you even upgrade to 64bit OSX
> if you want to with these older Macs (with 64bit CPUs)?
> Sounds like a really broken mess.. probably the DMD for OSX should stick
> to 32bit or universal binaries.

It might look messy, but in reality it's doesn't matter much. First, 
there is no 64-bit or 32-bit version of OS X, both versions are 
installed at the same time.

Second, the 32-bit kernel is able to run 64-bit programs just fine if 
you have a 64-bit CPU, just like the 64-bit kernel can run 32-bit 
programs. The reason very few Macs run the kernel in 64-bit in the 
current version of Mac OS X is to avoid breaking older 32-bit 
third-party drivers (which must run inside the kernel's address space).

So unless you do driver programming, you generally don't care at all in 
which mode the kernel is running. Note that which kernel to use is 
determined at boot time. You can hold the 6 and 4 keys while you boot 
to force the 64-bit kernel to be used.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/