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Re: How to correctly determine a small object?

From: Maxthon Chan
Subject: Re: How to correctly determine a small object?
Date: Sun, 09 Jun 2013 01:20:24 +0800

So I can safely do this? (Macro rewritten as inline function)

static inline __attribute__((always_inline)) BOOL objc_isSmallObject(id obj)
        return (((intptr_t)obj) & 1) ? YES : NO;

在 2013-6-8,上午4:10,David Chisnall <address@hidden> 写道:

> On 7 Jun 2013, at 16:29, Luboš Doležel <address@hidden> wrote:
>> for toll-free bridging in CoreBase, I need a way to detect whether the 
>> incoming pointer is a small object encoded in a pointer and act accordingly 
>> (treat it as an ObjC object and avoid reading it).
> In objc/runtime.h, there is a constant SMALL_OBJECT_MASK.  If ptr & 
> SMALL_OBJECT_MASK == 0, then the pointer is not a small object.
> On 32-bit platforms, the low bit of the pointer will be 0.  On 64-bit 
> platforms, the low 3 bits will always be zero.
> David
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