Re: The "black magic" of ioctl

[Simon Wright <simon@pushface.org>]

Florian Weimer <fw@deneb.enyo.de> writes:

> * Frank J. Lhota:
>
>> Actually, you can call a varargs function such as ioctl from
>> Ada. Declare each ioctl profile that you need, e.g.
>
> Perhaps it seems to work for you, but this is not portable.  There are
> popular targets where the varargs calling convention is markedly
> different from the non-varargs calling convention, such as amd64.  It
> might still work by accident, but all bets are off, really.

I hadn't realised this: but a quick scan of the GNAT sources confirms:
in socket.c,

* Wrapper for ioctl(2), which is a variadic function */

int
__gnat_socket_ioctl (int fd, int req, int *arg) {
#if defined (_WIN32)
  return ioctlsocket (fd, req, arg);
#else
  return ioctl (fd, req, arg);
#endif
}