Re: [PATCH 3/3] utils: Deprecate inexact fractional suffix sizes

[Eric Blake <eblake@redhat.com>]

On 2/5/21 5:10 AM, Daniel P. Berrangé wrote:
> On Thu, Feb 04, 2021 at 01:07:08PM -0600, Eric Blake wrote:
>> The value '1.1k' is inexact; 1126.4 bytes is not possible, so we
>> happen to truncate it to 1126.  Our use of fractional sizes is
>> intended for convenience, but when a user specifies a fraction that is
>> not a clean translation to binary, truncating/rounding behind their
>> backs can cause confusion.  Better is to deprecate inexact values,
>> which still leaves '1.5k' as valid, but alerts the user to spell out
>> their values as a precise byte number in cases where they are
>> currently being rounded.
> 
> I don't think we should be deprecating this, as I think it makes
> it very user hostile.  Users who require exact answers, won't be
> using fractional syntax in the first place. IOW, by using fractional
> syntax you've decided that approximation is acceptable. Given that,
> I should not have to worry about whether or not the fraction I'm
> using is exact or truncated. It is horrible usability to say that
> "1.1k" is invalid, while "1.5k" is valid - both are valid from my
> POV as a user of this.
> 
> 
> 
>> Note that values like '0.1G' in the testsuite need adjustment as a
>> result.
>>
>> Sadly, since qemu_strtosz() does not have an Err** parameter, we
>> pollute to stderr.
> 
> This is only an warning, so setting an Err ** would not be appropriate
> right now.
> 
> None the less we should add an Err **, because many of the callers
> want an Err ** object populated, or use error_report().

That is more effort.  What's the consensus - is it important enough that
I should spend that effort getting rid of technical debt by adding
versions of qemu_strto* that take Err** at this point in time?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org