Passing a pointer when a reference is required

Question

I have the following 2 functions:

void B::set(A * ptr){ this->a = ptr; this->info = get_some_info_from_a(*ptr); } T get_some_info_from_a(A& ref){ return ref.info; }

As you see, I have A * ptr as a pointer in set(...), but I would need a reference to call get_some_info_from_a(...). So I dereference ptr and give it as an argument.

Is that correct? Is it efficient given A has some resources which must be copied by a copy/move constructor? I ask the question because it really seems that this line introduces some mysterious bugs.

get_some_info_from_a never accesses the ref argument, but returns a global variable named info. Is that what it's supposed to do? — Freyja
– Freyja, Commented Jul 9, 2014 at 14:51
@Frxstrem I think the real code would work out info from ref. — Joseph Mansfield
– Joseph Mansfield, Commented Jul 9, 2014 at 14:52
Oh, that's embarassing. Of course info would be taken from ref. It's corrected now. — Michael
– Michael, Commented Jul 9, 2014 at 14:57

Joseph Mansfield · Accepted Answer · 2014-07-09 14:51:45Z

It's correct and efficient. Performing indirection with *ptr just gets you the value that ptr points to and then you are passing that by reference to get_some_info_from_a. That value is never copied.

BenMorel · Accepted Answer · 2014-07-10 08:35:37Z

This is fine and will not invoke any copy/move ctor as you are calling by reference. However, a const or two (if a member function) in the function signature wouldn't go a miss:

T get_some_info_from_a(const A& ref) const {

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