On 07/21/2014 01:33 PM, Markus Armbruster wrote:
John Snow <js...@redhat.com> writes:
On 07/21/2014 03:48 AM, Markus Armbruster wrote:
It certainly could check whether the value fits into uint64_t.
A quick peek at how string-input-visitor.c uses strtoll() makes me
cringe.
[...]
What I meant by that was to say that by the time a value was returned
to visit_type_uint64, the value has already been possibly converted
implicitly from a negative value, and we can't tell at this level if
that happened without re-inspecting the string we were passed. At that
point, why not just fix the string parsing mechanics one more layer
down in parse_type_int() -- or by creating another routine primitive;
i.e parse_type_uint.
As Eric Blake noted elsewhere in the thread, it would be nice to have
the ability to have three behaviors at the lowest level -- signed,
unsigned with wraparound, and unsigned strict. The biggest question in
my mind is how to add the property flag to allow authors to opt-in to
the unsigned with wraparound option, where the unsigned strict option
makes the most sense to me as a default.
Do we have a use case for silently mapping negative numbers to positive
ones?
Via Eric Blake, for cases where "-1" is a convenient shorthand for "MAX"
in lieu of writing out gibberish values like 4 billion or 18
quintillion. I don't know if anyone actually relies on this behavior,
but I don't know that they're not. I can easily imagine something like
--max-log-messages=-1, for instance.
eblake had said that libvirt recently made a similar parsing change and
they wound up with those three backing cases.
