From: Joseph Myers <joseph@codesourcery.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: <gcc@gcc.gnu.org>
Subject: Re: No-named-argument variadic functions
Date: Thu, 20 Oct 2022 16:35:20 +0000 [thread overview]
Message-ID: <alpine.DEB.2.22.394.2210201627430.71947@digraph.polyomino.org.uk> (raw)
In-Reply-To: <CAFiYyc1vsvqfTH=xSn0wdDQEO+QMd9-Fodf+ncx1yjszOTZOgg@mail.gmail.com>
On Thu, 20 Oct 2022, Richard Biener via Gcc wrote:
> > 1. How should (...) be represented differently from unprototyped functions
> > so that stdarg_p and prototype_p handle it properly? Should I add a new
> > language-independent type flag (there are plenty spare) to use for this?
>
> I'd say unprototyped should stay with a NULL TYPE_ARG_TYPES but
> a varargs function might change to have a TREE_LIST with a NULL type
> as the trailing element? Not sure if we want to change this also for
> varargs functions with actual arguments.
>
> If we want to go down the route with a flag on the function type then
> I'd rather flag the unprototyped case and leave varargs without any
> actual arguments as NULL TYPE_ARG_TYPES?
The issue with both of those options is that they don't seem very safe for
code that accesses TYPE_ARG_TYPES directly, of which I think we have a
lot. Such code is quite likely to fall over on a TREE_LIST with a NULL
type entry, and having code that encounters a (...) prototype treat it
like an unprototyped function seems safer than having code that encounters
an unprototyped function treat it like a (...) prototype because the code
that created the function type failed to set a flag to say it's
unprototyped.
(In principle TYPE_ARG_TYPES could change to have static type other than
tree, with explicit flags both for stdarg_p and for prototype_p, which
would provide GCC-build-time assurance that there's no non-updated code
left that expects an old representation. But that would be a very large
change.)
--
Joseph S. Myers
joseph@codesourcery.com
prev parent reply other threads:[~2022-10-20 16:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 23:53 Joseph Myers
2022-10-20 6:00 ` Richard Biener
2022-10-20 16:35 ` Joseph Myers [this message]
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