Re: [PATCH v2] docs/misra: document the expected sizes of integer types

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 25/03/2024 11:16, Jan Beulich wrote:
> On 22.03.2024 00:17, Julien Grall wrote:
> > Hi Stefano,
> >
> > I haven't fully read the thread. But I wanted to clarify something.
> >
> > On 21/03/2024 19:03, Stefano Stabellini wrote:
> > > > > Or possibly unsigned long depending on the parameter.
> > > > You're contradicting yourself: You mean to advocate for fixed-width types,
> > > > yet then you suggest "unsigned long".
> > > No. I explained it in another thread a couple of days ago. There are
> > > cases where we have fixed-width types but the type changes by
> > > architecture: 32-bit for 32-bit archs and 64-bit for 64-bit archs.
> > > Rather than having #ifdefs, which is also an option, that is the one
> > > case where using "unsigned long" could be a decent compromise. In this
> > > context "unsigned long" means register size (on ARM we even have
> > > register_t). Once you pick an architecture, the size is actually meant
> > > to be fixed. In fact, it is specified in this document. Which is one of
> > > the reasons why we have to use == in this document and not >=. In
> > > general, fixed-width types like uint32_t are better because they are
> > > clearer and unambiguous. When possible I think they should be our first
> > > choice in ABIs.
> > "unsigned long" is not fixed in a given architecture. It will change
> > base on the data model used by the OS. For instance, for Arm 64-bit, we
> > have 3 models: ILP32, LP64, LLP64. Only on LP64, 'unsigned long' is 32-bit.
> "... is 64-bit" you mean?
Whoops. Yes!

Cheers,

--
Julien Grall