Re: [Qemu-devel] [PATCH 3/3] Add test suite for json marshalling

[Anthony Liguori <anthony@codemonkey.ws>]

Jamie Lokier wrote:
> Anthony Liguori wrote:
>   
>> After checking that we can demarshal, marshal again and compared to
>> the expected decoded value.  This doesn't work so well for floats
>> because they cannot be accurately represented in decimal but we try
>> our best.
>>     
>
> Good sprintf/scanf/strtod implementations do guarantee that what's
> printed and then parsed gets back the same floating point value, as
> long as you have printed sufficient decimal digits.
>
> I'm not sure if FLT_DIG/DLB_DIG are the right number of digits,
> though.  Glibc's documentation of those is confusing and they might
> mean something a little different.
>   

Eh, I played around quite a bit and the results were disappointing.

$ printf "%f\n" 43.32
43.320000
$ printf "%0.32f\n" 43.32
43.31999999999999999972244424384371

Regards,

Anthony Liguori
> -- Jamie
>
>
>