On Fri, Aug 16, 2024 at 04:05:52PM +0000, Joseph Myers wrote:
> On Fri, 16 Aug 2024, Jakub Jelinek wrote:
>
> > > Apart from any consequences for arguments of prefix/suffix/is_empty
> > > (where
> > > there is a plausible argument that the argument should get expanded at
> > > some point and that the current wording is undesirable for usability),
> > > this would also mean that e.g.
> > >
> > > #define LIMIT limit
> > > #embed "file" LIMIT(1)
> > >
> > > isn't valid because LIMIT doesn't get expanded (the syntax for
> > > non-expanded #embed is met, with an unknown parameter LIMIT), while
> > >
> > > #define limit !
> > > #embed "file" limit(1)
> > >
> > > *is* valid, because limit doesn't get expanded (which may be convenient
> > > for usability - it means headers don't need to use __limit__ if using
> > > #embed, even if files including the header might have defined limit as a
> > > macro).
> >
> > Is there an agreement on that?
>
> I think it's understood to be what the words mean (apart from the recent
> discussion, also noted in February 2022 discussion - e.g.
> <https://www.open-std.org/jtc1/sc22/wg14/21635>). Whether it's desirable
> is another matter. Apart from likely wanting to be able to use macros
> within the prefix/suffix/if_empty arguments, it would also seem fairly
> reasonable to want to have a macro expanding to such parameters used with
> more than one directive.
>
> #define PARAMS prefix(X) suffix(Y)
>
> #embed "a" PARAMS
>
> #embed "b" PARAMS
>
> without needing to arrange for the directive not to look like one of the
> other forms before macro expansion.
>
> I've added this to my list of issues to file once we have an issue
> tracking system for the C standard in operation.
Ok. So for now, should I work on a patch variant which tries to follow
what is in C23 right now?
I.e. most likely set pfile->state.prevent_expansion = 1; initially,
keep checking the tokens just for the basic syntax match (header token or
string literal, followed by check for pp-parameter matches if any until end
of line, based on that decide and push all the read tokens back to
lookaside?
Still, as I wrote, not really sure if it goes with the
pfile->state.prevent_expansion = 1 decision when temporarily switching that
off for the limit argument real parsing when the closing ) (i.e.
non-balanced) comes from a macro, and whether to ignore the macro expansion
of prefix/suffix/if_empty altogether, or push those expanded when actually
using them (and if so, again, what to do with unbalanced case; maybe in that
case it would be desirable and would allow to insert unbalanced {,(,[,],),}
to the token stream).
> My concern here is more with the use of the fields in cpp_options, than
> with the initialization of that from lang_flags. Maybe that large
> lang_defaults table isn't the optimal way of initializing all those
> cpp_options fields (although initializing CPP_OPTION (pfile,
> embed_directive) from l->warning_directive would also be awkward; the
> question is more whether computing the cpp_options fields with logic like
> "C from version X onwards, C++ from version Y onwards" would be an
> improvement on a table taking 147 columns).
Ok, will change it. And think how to improve the table next.
Indeed, having some macro for this option is C >= n && C++ >= m, whether GNU
only or standard etc. would be nice.
Right now it is 28x23 bit matrix.
One possibility would be
/* u e w
b d 8 l a t
x u i i c v s s i r d r
x i d u r d n g t h a c z f n e u
c c n x c d s i l l l c s r l o o d l d d l f
9 + u i 1 i t g i i i s e i i p p f i e i i a
9 + m d 1 d d r t t t t p g t t e p t f r m l */
{ /* GNUC89 */ { 0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0 },
/* GNUC99 */ { 1,0,1,1,0,0,0,1,1,1,0,0,0,0,0,1,1,0,0,0,0,0,0 },
/* GNUC11 */ { 1,0,1,1,1,0,0,1,1,1,0,0,0,0,0,1,1,0,0,0,0,0,0 },
/* GNUC17 */ { 1,0,1,1,1,0,0,1,1,1,0,0,0,0,0,1,1,0,0,0,0,0,0 },
/* GNUC23 */ { 1,0,1,1,1,1,0,1,1,1,0,1,1,0,1,1,1,1,0,1,1,0,1 },
/* GNUC2Y */ { 1,0,1,1,1,1,0,1,1,1,0,1,1,0,1,1,1,1,0,1,1,0,1 },
/* STDC89 */ { 0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0 },
/* STDC94 */ { 0,0,0,0,0,0,1,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0 },
/* STDC99 */ { 1,0,1,1,0,0,1,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0 },
/* STDC11 */ { 1,0,1,1,1,0,1,1,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0 },
/* STDC17 */ { 1,0,1,1,1,0,1,1,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0 },
/* STDC23 */ { 1,0,1,1,1,1,1,1,1,0,0,1,1,0,1,1,1,1,0,1,1,0,1 },
/* STDC2Y */ { 1,0,1,1,1,1,1,1,1,0,0,1,1,0,1,1,1,1,0,1,1,0,1 },
/* GNUCXX */ { 0,1,1,1,0,1,0,1,0,0,0,0,0,0,0,1,1,0,0,0,0,0,1 },
/* CXX98 */ { 0,1,0,1,0,1,1,1,0,0,0,0,0,1,0,0,1,0,0,0,0,0,1 },
/* GNUCXX11 */ { 1,1,1,1,1,1,0,1,1,1,1,0,0,0,0,1,1,0,0,0,0,0,1 },
/* CXX11 */ { 1,1,0,1,1,1,1,1,1,1,1,0,0,1,0,0,1,0,0,0,0,0,1 },
/* GNUCXX14 */ { 1,1,1,1,1,1,0,1,1,1,1,1,1,0,0,1,1,0,0,0,0,0,1 },
/* CXX14 */ { 1,1,0,1,1,1,1,1,1,1,1,1,1,1,0,0,1,0,0,0,0,0,1 },
/* GNUCXX17 */ { 1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,1,0,0,0,0,0,1 },
/* CXX17 */ { 1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,1,0,0,0,0,0,1 },
/* GNUCXX20 */ { 1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,1,0,0,0,0,0,1 },
/* CXX20 */ { 1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,0,0,0,0,1 },
/* GNUCXX23 */ { 1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1 },
/* CXX23 */ { 1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1 },
/* GNUCXX26 */ { 1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1 },
/* CXX26 */ { 1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1 },
/* ASM */ { 0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 }
};
Jakub
