Re: wide function pointer type

[Anthony Green <green@moxielogic.com>]

Hi Martin,

  I haven't read the whole proposal yet, but I'll try to this week.  I
did, however, read the first paragraph, and it says:  "Trying to use
regular function pointers for callbacks with data requires run-time
code generation (e.g. nested functions in GCC or XL C, and closures in
libffi [1]) but this is complex, inefficient, and problematic from a
security point of view."

  This is no longer true for libffi on the important Linux platforms.
We use static code templates that are placed in memory at a fixed,
predetermined distance from the data they reference.  There is no
runtime code generation.  Well, to be fair, perhaps it is still
complex, but it's far more secure than before.

  Thanks for sharing.  I'm not a language expert, but I know others here are.

AG

On Sun, Oct 10, 2021 at 7:32 AM Martin Uecker via Libffi-discuss
<libffi-discuss@sourceware.org> wrote:
>
>
>
> Hi all,
>
> I will propose a wide function pointer type (actually
> a wide function type) to WG14 for C23 as a common
> type for callbacks, closures, which now require an
> additional void pointer argument in C APIs. This
> is intended to be compatible with ABIs with now
> use a static chain register.
>
> An early draft can be found here:
>
> http://wwwuser.gwdg.de/~muecker1/wide_v4.pdf
>
>
> I thought you might be interested and I would love
> to hear your feedback.
>
> Martin
>
>
>