Re: [Qemu-devel] [PATCH v2] virtio-rng: Add human-readable error message for negative max-bytes parameter

[John Snow <jsnow@redhat.com>]

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.

For now I will just fix the error message. We can draft ideas for how to 
fix the semantic issues in parsing later.