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From: Ian Collins <ian-news@hotmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Lets put it another way
Date: Wed, 25 May 2011 07:36:31 +1200
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On 05/25/11 12:58 AM, Paul wrote:
>
> "Ian Collins"<ian-news@hotmail.com>  wrote in message
> news:941ffpFt2pU22@mid.individual.net...
>> On 05/24/11 09:20 PM, Paul wrote:
>>>
>>> "Ian Collins"<ian-news@hotmail.com>   wrote in message
>>> news:940g82Ft2pU20@mid.individual.net...
>>>> On 05/24/11 01:14 PM, Paul wrote:
>>>>> Ok in connection to my previous post, lets remove the null pointer
>>>>> issue
>>>>> and
>>>>> consider this:
>>>>>
>>>>> #include<iostream>
>>>>>
>>>>> typedef int (*pparr)[3];
>>>>>
>>>>> int main(){
>>>>>     pparr p1 = (pparr)new int[3];
>>>>>     pparr p2= p1;
>>>>>     delete[] p1;
>>>>>     std::cout<<    *p2<<std::endl;
>>>>
>>>> UB yet again.
>>>>
>>>>>     std::cout<<    typeid(*p2).name();
>>>>> }
>>>>>
>>>>>
>>>>> In the last 2 lines does an array type object exist, even though there
>>>>> is
>>>>> no
>>>>> array object?
>>>>
>>>> No.
>>>>
>>>>> If not what is the object that stores the address and is interpreted as
>>>>> an
>>>>> array type by the typeid expression?
>>>>
>>>> The typeid and sizeof operators do not evaluate their expression (unless
>>>> in case of typeid the type is polymorphic).  So no object is required.
>>>>
>>> You do not seem to understand the question.
>>
>> You do not appear to understand the answer.
>>
>>> I said ..if not what is the object that stores the address?
>>> So what is this object? Do you know?
>>
>> There isn't an object.  The compiler knows the type of *p2.  You may as
>> well have written
>>
>> #include<iostream>
>> #include<typeinfo>
>>
>> typedef int (*pparr)[3];
>>
>> int main(){
>>    pparr p2;
>>    std::cout<<  typeid(*p2).name()<<  std::endl;
>> }
>>
>>
> You are not addressing the what stores the memory address.

Because there isn't an address to store.  The typeid operator (like 
sizeof) works with types, not values.  In a simple case such as this the 
operand is not evaluated.  Until you understand this you will be stuck 
in limbo.

I could have simplified my simplification further by writing

std::cout << typeid(int[3]).name() << std::endl;

See?  No memory address just a type.

> A memory address value is stored so there must be an object to store this
> value, you say there is no object so what is it that stores this value?

There isn't an address.  Where's the address in typeid(int).name()?  Or 
sizeof(int)?

-- 
Ian Collins