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SubjectRe: [PATCH 0/6] RFC: Typesafe callbacks
Date
On Monday 21 January 2008 00:00:52 Tejun Heo wrote:
> What should be do are
>
> * Check that the threadfn's argument fits into void *.

For everything but timer, you'll get a warning if the data isn't assignable to
a void *, so you get a warning if you use a non-pointer already.

But it would be cool to allow functions which take an unsigned long. To do
this, I think that would need to be a special case for the data arg (which
we'd really want to wrap in a macro), like:

/* If fn expects an unsigned long, cast the data. If not, we'll
* get a warning if data is not void * compatible. */
__builtin_choose_expr(__builtin_compatible_p(typeof(1?(threadfn):NULL),
int (*)(unsigned long)),
(void *)(unsigned long)(data), (data))

> * Trigger overflow in implicit constant conversion warning if the
> specified data is too large for the argument type.

Hmm, u64 on 32-bit platforms? I think that will fail the above test: the type
of the function ptr will be "int (*)(u64)" and so you'll end up passing data
(a u64) to a void * argument, which will elicit a warning...

I'll test this out and see what I can make...

Thanks!
Rusty.


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