Re: Mangled function prototypes (phantom arguments)

Alejandro Colomar <[email protected]> Wed, 27 May 2026 19:58:28 +0200

Newsgroups	org.kernel.vger.linux-man
Message-ID	<ahcvtYzeadqmhk62@devuan>

Hi Michael,

On 2026-05-27T18:46:06+0200, Michael Kerrisk (man7.org) wrote:
> Hello Alex,
> 
> Thanks for responding.
> 
> > > The problems have all resulted in prototypes adding a phantom first
> > > argument. See for example this prototype from read.2:
> > >
> > >        ssize_t read(size_t count;
> > >                     int fd, void buf[count], size_t count);
> >
> > This is valid C (except for the array of void, but that's a separate
> > topic).
> 
> As we see, I'm not keeping up with my C :-).

To be fair, this is a very little-known feature (even though it's a very
old one).  I (and a few others) are trying to make it more well known,
as it's quite interesting.

> 
> Is this a GNU extension? Or part of the standard? Or an upcoming part
> of the standard?

It is a very old GNU extension.  For decades, almost nobody had been
interested in it (I've never seen it used in the wild).  One or two
years ago, we started discussing it in the C Committee; several of us
want it to be standard.  However, Clang is vetoing it.

Cheers,
Alex

> 
> Thanks,
> 
> Michael

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

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