Charles L. Nelson wrote:
> I think that on some systems it is possible to tell the compiler to use
> 32-bit addresses and pointers while ints are 32-bits and longs are 64-bits.

> This is the default ABI on many 64-bit machines unless it is overridden.

I don't think so. Most 64-bit archs should be using LP64. I wonder what
architecture you have mind. There are certainly all kinds of combinations
but LP64 is the most popular.
 
> Also, there are only a few 64-bit architectures that can make use of true
> 64-bit addressing.  While the compiler may allow 64-scalar addressing in the
> source code, somewhere in the build process, the address is usually munged
> down to the size of the MMU quantum which can be 36-bit, 40-bit or 56-bit
> depending on architecture.

Sure but how does that help with memory usage in C? I haven't seen 48-bit
pointers using only 6 bytes. Even if only 48 bits are relevant pointers still
consume full 64 bit or 8 bytes of memory.

-- 
Christian