Re: lldb 'print object' (po) prints pointer value if not object?
Re: lldb 'print object' (po) prints pointer value if not object?
- Subject: Re: lldb 'print object' (po) prints pointer value if not object?
- From: Roland King <email@hidden>
- Date: Wed, 23 Apr 2014 13:37:25 +0800
So if that is a tagged pointer then some of those bits represent the fact it's tagged (the LSB) and what type it is (who knows how many others, possibly the next 3), so if it is an NSNumber representing an integer, the value is shifted up some number of bits, past the tag bits, so the value wouldn't be 83, it might be 5 (>>4), or zero (>>8), or something else.
So going back to the original question, po returning 83 is probably not the right answer either way.
Might be the way 'po' is mapped to an underlying LLDB native 100 character long command?
On 23 Apr, 2014, at 1:28 pm, Jerry Krinock <email@hidden> wrote:
> Thank you, Quincey. I’d read about tagged pointers, but being a high level guy, I guess I’ve never seen one in real life :))
>
> My example arose while debugging a crash. There was *supposed* to be an object in rdi, but apparently it was deallocced and possibly replaced by an NSNumber whose value is 83. So this is a variation on the case of finding a different object where your deallocced object had been.
>
> On 2014 Apr 22, at 22:04, Quincey Morris <email@hidden> wrote:
>
>> On Apr 22, 2014, at 22:00 , Roland King <email@hidden> wrote:
>>
>>> What do they do for all the even numbers then?
>>
>> I’m sorry, even numbers have been abolished. Didn’t you know?
>
> Let’s be nice. Non-aligned *pointers* have indeed been abolished, as explained here…
>
> https://www.mikeash.com/pyblog/friday-qa-2012-07-27-lets-build-tagged-pointers.html
>
>
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