Am 8. August 2024 13:28:57 MESZ schrieb Joseph Myers <josmy...@redhat.com>:
> On Thu, 8 Aug 2024, Alejandro Colomar wrote:
>
> > Hi Jens,
> >
> > On Thu, Aug 08, 2024 at 11:13:02AM GMT, Jens Gustedt wrote:
> > > > but to maintain expectations, I think it would be better to do
> > > > the same here.
> > >
> > > Just to compare, the recent additions in C23 typeof etc. only have the
> > > parenthesized versions. So there would be precedent. And it really
> > > eases transition
> >
> > Hmmm, interesting.
> >
> > The good part of reusing sizeof syntax is that I can reuse internal code
> > for sizeof. But I'll check if I can change it easily to only support
> > parens.
>
> Since typeof produces a type, it's used in different syntactic contexts
> from sizeof, so has different ambiguity issues, and requiring parentheses
> with typeof is not relevant to sizeof/lengthof. I think lengthof should
> follow sizeof. Make sure there's a testcase for lengthof applied to a
> compound literal (the case that illustrates how, on parsing sizeof
> (type-name), the compiler needs to see what comes after (type-name) to
> determine whether it's actually sizeof applied to an expression (if '{'
> follows) or to a type (otherwise)). (If you're following the sizeof
> implementation closely enough, this should just work.)
>
> --
> Joseph S. Myers
> josmy...@redhat.com
>
Hi,
I am not convinced that we should introduce the same syntax weirdness
for this feature. sizeof seems to be the only place in the core language
where a keyword is used as an operator in expressions, and
that does not resemble function-call notation. In particular your
example with compound literals shows that we could avoid syntax look-ahead
by not doing this. (People argued violently against look-ahead when we
discussed possible inclusion of lambdas into C23)
We don't have to repeat all historic accidents when inventing a new feature.
Sure that gcc may invent anything to their liking, but when and if we pass this
for standardisation we will give such considerations a careful look.
Jens
--
Jens Gustedt - INRIA & ICube, Strasbourg, France
