Re: Uniform vector lengths -- how long?

[Rob Browning]

Kevin Ryde <address@hidden> writes:

> I suppose, though personally I wouldn't feel any great urgency for
> that.  A positive inum ends up only, what, 3 bits less than a ulong,
> and a 512Mb array would be more than likely bigger than one could do
> real work with on a 32-bit machine.
>
> What is worth worrying about though would be making sure the "len *
> uvec_sizes[type]" in make_uvec doesn't overflow, perhaps wrapping
> around to a small size which is successfully malloced.  I guess
> currently with a maximum 8 in uvec_sizes and maximum
> MOST_POSITIVE_INUM for the count it's ok.

OK, I've fixed both of these.  After talking to Marius, I reworked
srfi-4 to use size_t for the length, since (as he pointed out) that's
what you'll eventually pass to malloc, and we will just make the
assertion that size_t must fit in a cell.

I also added checking to make_uvec to avoid the possibility of
overflow with types bigger than 1 byte.  Although the current solution
depends on SIZE_MAX being defined, and we wondered if it's
sufficiently common.

  if (len > ((size_t) SIZE_MAX / uvec_sizes[type])) ...

(I'll commit after I have a chance to double check the work.)

Thanks
-- 
Rob Browning
rlb @defaultvalue.org and @debian.org; previously @cs.utexas.edu
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