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Postings from February 2002
On Mon, 11 Feb 2002, Bryan C. Warnock wrote:
> On Monday 11 February 2002 15:37, Gregor N. Purdy wrote:
> > IIRC sizeof(opcode_t) === 4, since it is required that opcode_t be 32
> > bits. So, that 4 is supposed to be a 4, although turning it into a
> > symbolic constant is not a bad idea. Using sizeof(opcode_t) as that
> > constant isn't evil either, although I don't think its necessary.
>
> Nope. sizeof(opcode_t) >= 32 and sizeof(opcode_t) <= sizeof(INTVAL).
> The *contents* are limited to 32 bits, but the container is not. (64-bit
> efficiency hack.)
It's much more than just an efficiency hack. A legal C implementation can
actually have no 32-bit type. It is perfectly legal to have sizeof(short)
== sizeof(int) == sizeof(long) == 8 (64-bit), and some Crays indeed work
exactly that way. I don't think we want to force such systems to use
bitfields or some such for opcodes.
Further, though the contents are *supposed* to be limited to 32 bits, I
didn't come across any place in the code where that limit was actually
imposed.
--
Andy Dougherty doughera@lafayette.edu
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