MESSAGE
| DATE | 2016-12-10 |
| FROM | Ruben Safir
|
| SUBJECT | Re: [Learn] references to pointers
|
From learn-bounces-at-nylxs.com Sat Dec 10 22:53:12 2016
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From: Ruben Safir
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Date: Sat, 10 Dec 2016 22:53:09 -0500
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Subject: Re: [Learn] references to pointers
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[This mail was also posted to comp.lang.c++.]
On Sat, 10 Dec 2016 18:29:06 -0800, Barry Schwarz wrote:
>>What is the difference between these two statements
>>
>> unsigned char * &index(unsigned char * value){
>> index_ = value;
>> return index_;
>> };
>>
>>and without the reference:
>>
>> unsigned char * index(unsigned char * value){
>> index_ = value;
>> return index_;
>> };
>
> After you fix the errors so that the functions can compile cleanly:
>
> The first invokes undefined behavior (or is it a constraint
> violation) because it returns a reference to an object that will
> disappear as soon as the function ends.
>
> The second returns the value of that object and that will survive
> the destruction of index_ with no problem.
right. index_ is actually a data member of the object which this
function is a member of.
it points to a member of allocated memory which contains an image.
the second returns the address to a char within that memory which index_
points to.
The second one returns an lvalue reference of a pointer to char.
What practical difference is there in this case?
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