Re: Backport request (was: [PATCH v2] tools: convert bitfields to unsigned type)

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.07.2023 18:16, Jan Beulich wrote:
> On 04.07.2023 18:10, Roger Pau Monné wrote:
>> On Tue, Jul 04, 2023 at 06:04:36PM +0200, Jan Beulich wrote:
>>> On 04.07.2023 17:55, Roger Pau Monné wrote:
>>>> On Tue, Jul 04, 2023 at 05:42:33PM +0200, Jan Beulich wrote:
>>>>> Plus is the mentioned
>>>>> "potential ABI change" safe to take on a stable branch? There's not going 
>>>>> to
>>>>> be any SONAME change ...
>>>>
>>>> Is there any ABI change in practice? Both fields will still have a 1bit
>>>> size.
>>>
>>> But what a consumer of the interface reads out of such a field would change
>>> in case their compiler settings arrange for signed bitfields when signedness
>>> isn't explicit. We don't dictate, after all, what compiler settings to use
>>> with our interfaces (which generally is good, but which bites us here).
>>
>> Hm, I see.  I would argue that sign doesn't matter here, as those are
>> intended to be booleans, so anything different than 0 would map to
>> `true`.  But implementation might have hard coded TRUE to -1, and the
>> change would then break them?
> 
> That's a possible scenario I'm wary of here, yes.
> 
>> I'm failing to see that, because those implementations would still use
>> the old struct declarations they have been built with, and hence would
>> still threat it as signed?
> 
> Until they rebuild against the updated header, without any change to
> their code.
> 
> Anthony - do you have any thoughts here?

Btw in the meantime I'll queue the uncontroversial part of the patch
for backport (with a respective not about what was dropped).

Jan