Re: [PATCH 1/1] man/man2/request_key.2: Add missing GNU size forward-declarations

[Alejandro Colomar <alx@kernel.org>]

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Hi Mark,

> Date: 2026-09-14 10:19:13-0700
> From: Mark Harris <mark.hsj@gmail.com>
>
> Alejandro Colomar wrote:
> > > Anyway N3207 (spec mentioned in d2c2db883) is something I'll need to get used to :).
> >
> > There's a more recent paper with a slightly better spec (also compatible
> > with GCC): N3681.
> > <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3681.pdf>
> 
> There is an even more recent paper addressing this subject, N3923
> <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3923.pdf>,

Indeed, there's that newer proposal.  It's a different one, though.

> and the
> outcome from the last WG14 meeting was strong direction to proceed
> along these lines.

The actual poll results are 15 in favour, 7 against, and 4 abstentions.
I wouldn't have called that "strong direction to proceed".  I know
that's what the minutes say, but I don't agree with how polls are taken
as strong direction.  7 votes against is quite vocal opposition.

Here's a summary of the room feelings:
The committee was more or less (including myself) saying "as a user, I'd
like it, but as an implementor, it'd probably be a nightmare; as long as
implementors are okay with it, we're fine".  There was a comment from
one implementor of a small C compiler which essentially said it was
un-implementable for them, which raised some concerns.  From the
minutes:

	Uecker:	The SlimCC developer and another compiler developer
		wrote in a discussion about general features that they
		are worried about parameters for active declaration
		scoping.  It is difficult for them to implement this.
		They would rather implement template C++ functions.

I suggested a way forward: first, write a proposal prohibiting the use
of parameter names in array length expressions that clash with variables
declared at an outer scope.  The wording would look like this (taken
from n3923 itself):

    6.7.7.4  Function declarators
	@@ p4+1
	+Within a parameter declaration list,
	+if an identifier used in a parameter’s array bound expression
	+refers to a name declared later in the same list,
	+no declaration of an identifier with the same name
	+shall be visible from an enclosing scope.

This would require that the following code results in a diagnostic:

	int n;
	void foo(int a[n], int n);

But it would allow the following code without diagnostics:

	int n;
	void bar(int n, int a[n]);
	void baz(int a[n]);

This is obviously a good constraint, since it disallows code that is
most likely already broken, and doesn't affect code that works fine.

Once that constraint is in place, we could add --as a second proposal--
retroactive declaration of parameters being optional (so that small
compilers can say they don't support it), but we'll be sure that code
will not misbehave on such compilers.

>  Hopefully this much more human-readable approach
> will prevail and we can do away with these confusing forward
> declarations in parameter lists.

Agree.


Have a lovely day!
Alex

> 
>  - Mark

-- 
<https://www.alejandro-colomar.es>

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