On Aug 10, 2005, at 6:02 PM, Nathaniel Gray wrote:
Is there any way to send float or double arguments to a method
designated at runtime? I've tried using objc_msgSendv, casting it
in various ways, and using -performv::, but nothing works.
Using objc_msgSendv() properly requires knowledge of your
platform's ABI. In particular, floating-point values must be stored
in a special place in the marg_list on PowerPC. objc-msg-ppc.s
notes some of the details.
I saw this comment, but it doesn't jive with the offsets I get when I
use the marg_* macros:
* ... So the "marg_list" is actually:
*
* typedef struct objc_sendv_margs {
* double floatingPointArgs[13];
* int linkageArea[6];
* int registerArgs[8];
* int stackArgs[variable];
* };
The offsets from method_getArgumentInfo() just start at 0. This
suggests I should be using marg_adjustedOffset(), but if so I don't
understand why things don't break for integer arguments when I use
offsets from zero... :-/
Better options may be:
* using NSInvocation. It shields you from the ABI details.
I noticed NSInvocation but it seemed like quite a heavyweight
solution. I count 5+n messages for an n-argument method call. It
does appear to work, however, and I suppose that counts for
something. ;^) Actually, I haven't timed anything yet so I can't
say how that compares to an objc_msgSendv solution.
* using objc_msgSend() or objc_msgSend_stret() directly. Cast
objc_msgSend() to a function pointer type that matches your
method's signature, then make the call.
No-can-do. I don't know the method's signature at compile time.
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