Re: Header conformance/improvements (part 2)

[Jens Gustedt <jens.gustedt@inria.fr>]

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Hello Rich,

On Sat, 24 Feb 2018 19:17:45 -0500 Rich Felker <dalias@libc.org> wrote:

> > > I don't think this is any actual diference; the const keyword is
> > > a nop there. Issue 844 is just about the standard gratuitously
> > > including a do-nothing keyword there.  
> > 
> > Right. Keeping the qualifier here is harmless.  
> 
> Oh, I read it backwards and thought we lacked the const. I'm in favor
> of removing redundant/meaningless stuff in declarations. BTW all
> instances of __restrict except one or two (pointer-to-__restrict) are
> also of this type; they're meaningless in the declaration and perhaps
> should be removed.

You are right concerning the validity of the interface, and I agree
that the const should be removed. It contains no valuable information
for the caller.

The restrict information is different. Restrict is a important
contract with the caller, and it is really a pitty that it cannot be
enforced. Nevertheless compilers can (and should) diagnose violations
of the restrict contract that it is able to deduce from the visible
code. So I think such information should not be removed from
interfaces.


> > > Ah. This is problematic because functions declared in inttypes.h
> > > require wchar_t to prototype. Of course a shadow name for the same
> > > type can be defined (like how va_list is handled) but it's ugly...
> > >  
>  [...]  
> > >
> > > Similar issue. It could be fixed with a shadot typedef or explicit
> > > "struct _IO_FILE". The latter is ugly and something of a
> > > violation of the abstraction, I think..  
> > 
> > Indeed. I think ISO C should have exposed these data types.  
> 
> I agree. Maybe we should change it though. I'll think about it. I know
> there were tests (I think gcc fixincludes mess) flagging spurious
> exposure of va_list as a bug, and in principle someone might decide to
> do the same here, but maybe we should wait to make any change until
> if/when there's a problem.

I agree, all C library header specifications in the standard should
force all types of their interfaces exposed. I note that as a
modification request for C2x, but I would not at all be sure that such
a change would be consensual, and such a change would still be only in
years to come.



Thanks
Jens

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