Re: [PATCH v3 2/3] docs/devel/style: add a section about bitfield, and disallow them for packed structures

[Philippe Mathieu-Daudé]

On 10/12/24 08:52, Thomas Huth wrote:
> On 09/12/2024 21.33, Philippe Mathieu-Daudé wrote:
> > On 28/11/24 21:15, Pierrick Bouvier wrote:
> > > Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
> ...
> > > +For this reason, we disallow usage of bitfields in packed structures 
> > > and in any
> > > +structures which are supposed to exactly match a specific layout in 
> > > guest
> > > +memory. Some existing code may use it, and we carefully ensured the 
> > > layout was
> > > +the one expected.
> > > +
> > > +We also suggest avoiding bitfields even in structures where the exact
> > > +layout does not matter, unless you can show that they provide a 
> > > significant
> > > +memory usage or usability benefit.
> >
> > I don't think we should mention "significant memory usage benefit".
>
> Why not? That's the point of bitfields, isn't it? Or do you mean it's 
> included in "usability benefit" already?

To not generate a reactance effect :) Developers trying to optimize
memory usage via bit field uses is extremely rare (at least in the
QEMU community).

Anyhow, I don't object to this patch as is.