Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 5/5] typesafe: TIMER_INITIALIZER and setup_timer | Date | Mon, 10 Mar 2008 12:07:19 +1100 |
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On Thursday 06 March 2008 21:40:35 Al Viro wrote: > extern void decay_to_pointer(void const volatile *); > #define check_callback_type(f,x) (sizeof((0 ? decay_to_pointer(x),(f)(x) : > (void)0), 0)) #define __setup_timer(timer, func, arg) \ > do { \ > struct timer_list *__timer = (timer); \ > __timer->function = (void (*)(unsigned long))(func); \ > __timer->data = (unsigned long)(arg); \ > (void)check_callback_type(func, arg); \ > } while(0)
Thanks for that snippet; it's much more complete than the last one I found. I especially like the handling of const- and volatile-taking callback fns. My version is uglier, pasted below.
There are three problems I see here. First, the lack of warning for "void intfn(int); DECLARE_TIMER(t, intfn, 0);", but that's relatively minor. Second, the change of all the users is just churn, with cast_if_type() it can be done over the next couple of years, if ever.
Worst, I can't see a way to apply your technique in general, for non-void-returning functions (eg. interrupt handlers).
Here's the typesafe_cb () helper function from ccan (there are also typesafe_cb_preargs and postargs for callbacks with extra args):
/* Doesn't handle const volatile, but can be added. */ #define typesafe_cb(rettype, fn, arg) \ cast_if_type(cast_if_type(cast_if_type((fn), \ rettype (*)(const typeof(arg)), \ rettype (*)(void *)), \ rettype (*)(volatile typeof(arg)), \ rettype (*)(void *)), \ rettype (*)(typeof(arg)), \ rettype (*)(void *))
> PS: apologies for missing your previous mail; ETOOBIGMBOX ;-/
That's fine, happens to all of us. I was a little disappointed to return from holiday to discover that either your work or mine hadn't been merged tho :)
Cheers, Rusty.
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