Re: [RFC] timers, pointers to functions and type safety

[Al Viro <viro@ftp.linux.org.uk>]

On Sat, Dec 02, 2006 at 04:23:32AM -0500, Kyle Moffett wrote:
> On Dec 01, 2006, at 12:21:49, Al Viro wrote:
> >And that's where it gets interesting.  It would be very nice to get to
> >the following situation:
> > * callbacks are void (*)(void *)
> > * data is void *
> > * instances can take void * or pointer to object type
> > * a macro SETUP_TIMER(timer, func, data) sets callback and data  
> >and checks if func(data) would be valid.
> 
> This is where a very limited form of C++ templates would do nicely;  
> you could define something like the following:
> 
> template <typename T>
> static inline void setup_timer(struct timer_list *timer,
> 		void (*function)(T *), T *data)
> {
> 	timer->function = (void (*)(void *))function;
> 	timer->data = (void *)data;
> 	init_timer(timer);
> }
> 
> Any attempts to call it with mismatched "function" and "data"  
> arguments would display an "Unable to find matching template" error  
> from the compiler.
> 
> Unfortunately you can't get simple templated functions without  
> opening the whole barrel of monkeys involved with C++ support;  

Fortunately, you can get all checks done by gcc without involving C++ (or
related flamewars).  See original post for a way to do it in a macro
and for fsck sake, leave gcc@gcc.gnu.org out of it.

Folks, please trim the Cc.  My apologies for cross-posting in the first place,
should've double-posted instead and manually forwarded relevant followups...