passing a pointer by reference in c++

Question

I have a function where I'm passing in an iterator to a char * buffer (which is also a char *). The function needs to increment the iterator. Anyway, I found that a good method of passsing the iterator into the function is by passing the pointer by reference:

bool myFunction(unsigned char * &iter) { ...

However, I've heard that this is bad form and could cause problems. Here is the method that my coworker suggested I use:

typedef unsigned char * unsignedcharptr; bool myFunction(unsignedcharptr &iter) { ...

It looks to me like they're both doing the same thing. Is there a compiler difference between these two methods (I'm using Visual Studio 2005)? Which is correct?

I would rather consider typedefs for pointer types bad form to cause problems, but well, for the compiler there isn't any difference. — Christian Rau
– Christian Rau, Commented Feb 10, 2012 at 16:53
why not return a distance to increment by instead of modifying the pointer? — Anycorn
– Anycorn, Commented Feb 10, 2012 at 16:54
Semantically there is no difference, but yes second one is mostly preferred, typededs are easy to read. — Mr.Anubis
– Mr.Anubis, Commented Feb 10, 2012 at 16:55
typedef creates an alias for an existing type, and used for readability purposes mostly. — a1ex07
– a1ex07, Commented Feb 10, 2012 at 16:55
@Mr.Anubis Well, just until you forget that iter is a pointer and not an object. A * just says so much more than a ptr inside a long type name. — Christian Rau
– Christian Rau, Commented Feb 10, 2012 at 17:03

Luchian Grigore · Accepted Answer · 2012-02-10 16:53:46Z

7

I don't think there's any difference between the two. You should ask your coworker why he believes there is.

What might be the cause is for maintainability, where if you wanted to switch from unsigned char * to char * you'd only have to change one place. But this, I think, could lead to other problems.

answered Feb 10, 2012 at 16:53

Luchian Grigore

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3 Comments

Luchian Grigore Over a year ago

@Adrian that's subjective though. I find unsigned char* more readable than unsignedintptr, while some comments suggest otherwise. What do you think?

Joe Lyga Over a year ago

Nah, it wasn't about readability. I think she thinks that it would cause memory issues.

Mr.Anubis Over a year ago

@JoeLyga I don't know what you both think exclusively xD but she got that wrong if you talk about your particular above code example.

Robᵩ · Accepted Answer · 2012-02-10 17:17:21Z

Is there a compiler difference between these two methods (I'm using Visual Studio 2005)?

As others have correctly noted, "no".

Which is correct?

Between the two alternatives, it entirely comes down to the "should I hide pointers behind typedefs" debate. There are valid arguments for either position

However, I think that both of your code snippets suffer from over-specialization. I prefer to code algorithms as template functions so that I Don't Repeat Myself.

If your design supports it, you could generalize your code to accept any iterator:

template <class InputIterator> bool myFunction(InputIterator &iter) { std::cout << *iter; ++iter; return true; }

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