Re: [Libguestfs] [PATCH v3 1/4] mltools: Rename Yajl module as JSON_parser and move to common/mltools.

On 08/17/2018 10:48 AM, Richard W.M. Jones wrote: >On Fri, Aug 17, 2018 at 10:30:35AM -0500, Eric Blake wrote: >>On 08/17/2018 10:16 AM, Richard W.M. Jones wrote: >>>Commit bd1c5c9f4dcf38458099db8a0bf4659a07ef055d changed all the code >>>to use Jansson instead of yajl. However it didn't change the OCaml >>>API name (which was still Yajl). >>> >> >>Are you aware that Jansson can't parse all JSON generated by qemu, >>and that the developers of Jansson did not seem sympathetic to >>patches that would make it possible? Libvirt recently reverted >>their use of Jansson because of its inability to deal with unsigned >>64-bit numbers (and sadly, RFC7159 does not define bounds for what >>forms valid JSON numbers, but merely leaves it up to implementations >>to decide for themselves). > >Yes, painfully aware. Not sure what to do about it however, since the >alternative (ie. switching back to yajl) as libvirt did is not going >to be pleasant. > >Currently we're OK as long as disk sizes don't exceed 8 petabytes, if >my quick calculation is correct. The problem comes anywhere that qemu outputs an unsigned 64-bit number as unsigned AND where that value is larger than INT64_MAX (jansson uses strtoll, rather than strtoull). But since disk sizes cannot exceed off_t, which is a signed 64-bit number, it does not matter whether qemu outputs those as signed or unsigned - they will still be parseable as a signed number. Thus, you are correct that disk sizes in qemu output won't trigger the Jansson limitation.