On Oct 11, 2010, at 10:13 PM, Dave Keck wrote:
>> Don't do that. object_getInstanceVariable() and object_setInstanceVariable()
>> still assume the ivar is of an object pointer type.
>
> As the documentation and prototypes stand, one would think that
> object_getInstanceVariable() could be used like this:
>
> double *doublePointer = nil;
> object_getInstanceVariable(..., (void **)&doublePointer);
> NSLog(@"%f", *doublePointer); // get ivar value
> *doublePointer = 42.4242; // set ivar value (erroneously bypassing
> potential GC write barriers if it were a pointer type)
>
> ... especially since outValue is documented as "On return, contains a
> pointer to the value of the instance variable." In fact, I suppose it
> should read "On return, contains the value of a pointer-typed instance
> variable."
The function writes the ivar's value to *outValue. Please file a bug report if
you don't like the documentation.
> Furthermore, if object_getInstanceVariable() assumes an "object
> pointer type" -- emphasis on _object_ -- shouldn't outValue be typed
> {id *}?
It happens to work for pointer-size non-object values. We'd probably deprecate
it rather than changing the prototype at this point.
--
Greg Parker gpar...@apple.com Runtime Wrangler
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