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Re: [commit] new observer.[hc] files
On Fri, Feb 28, 2003 at 11:17:10AM -0500, Andrew Cagney wrote:
> >static void
> >>observer_normal_stop_notification_stub (const void *data,
> >> const void *unused_args)
> >>{
> >> observer_normal_stop_ftype *notify = (observer_normal_stop_ftype *)
> >> data;
> >> (*notify) ();
> >>}
> >
> >
> >Is this extra indirection really necessary? Because I'm 99% sure it
> >won't work on several 64-bit platforms. Function pointers and data
> >pointers are not required to have the same size; on IA-64 I believe
> >that a function pointer is 128 bits and a data pointer is 64 bits.
>
> Like the PowerABI? That has a 32 bit pointer but a 64 bit function
> descriptor. void* ends up containing the address of the function
> descriptor. Anyway, "defs.h" has the comment:
>
> /* NOTE: cagney/2000-03-04: This typedef is strictly for the
> make_cleanup function declarations below. Do not use this typedef
> as a cast when passing functions into the make_cleanup() code.
> Instead either use a bounce function or add a wrapper function.
> Calling a f(char*) function with f(void*) is non-portable. */
> typedef void (make_cleanup_ftype) (void *);
>
> Once the code gets converted into a SED script, it can always be changed
> to something more strict.
>
> >Why not require all observer functions to take the same arguments
> >instead?
>
> Per the original thread, it is to ensure strongly typed interfaces.
OK, that makes good sense. Anyway, my concerns about casting a
function pointer to void* seem to have be moot; we can eliminate some
of the grossness when/if this becomes a generated file.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer