Front page | perl.perl5.porters |
Postings from June 2022
On 6/28/22 20:27, hv@crypt.org wrote:
> Karl Williamson <public@khwilliamson.com> wrote:
> : Then the loop innards would look like:
> :
> : while (s < e) {
> : code_point = next_uvchr(s, e, &retlen);
> :
> : if (retlen < 0) {
>
> I'd recommend making this `if (retlen <= 0) {` or otherwise handling
> the retlen == 0 case, even if you only expect that when s >= e: the
> function should be capable of doing something reasonable on an empty
> string, which probably means not croaking.
>
> : ... process error ...
> : retlen = -retlen;
> : }
>
> Hugo
It is currently illegal to call the existing functions with zero length
input. The functions don't now croak on zero length input, but they do
assert against it, which on DEBUGGING builds is pretty much the same thing.
IIRC the reason is performance to avoid an essentially useless
conditional, which otherwise would penalize everyone. Since this is XS
code calling us, there are plenty of other attack vectors available for
a malicious call.
retlen is guaranteed to never be 0. Even is s==e, the code would
attempt to read a byte, and if it didn't segfault, that byte is
guaranteed to indicate a non-zero length
Thread Previous
|
Thread Next