Passing a Pointer by Reference in C++ – Techniques and Examples

c++pointersreference

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?

Best Answer

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.

Related Solutions

C++ Pointers – Passing References to Pointers in C++

Your function expects a reference to an actual string pointer in the calling scope, not an anonymous string pointer. Thus:

string s;
string* _s = &s;
myfunc(_s);

should compile just fine.

However, this is only useful if you intend to modify the pointer you pass to the function. If you intend to modify the string itself you should use a reference to the string as Sake suggested. With that in mind it should be more obvious why the compiler complains about you original code. In your code the pointer is created 'on the fly', modifying that pointer would have no consequence and that is not what is intended. The idea of a reference (vs. a pointer) is that a reference always points to an actual object.

C++ Pointers – How to Pass a Pointer Variable as a Reference Parameter

I want to pass a pointer by reference, but I'm not sure how to do that.

For this, consider the following snippet

#include <iostream>

void test(int*& t)
{
    t = nullptr;
}

int main()
{
    int* i = new int(4);

    test(i);

    if (i == nullptr)
        std::cout << "I was passed by reference" << std::endl;
}

in which is is passed by reference to test, where it is set to nullptr and the program prints: I was passed by reference.

I think this example should make clear how to pass a pointer by reference to a function.

So in your case the function signiture must change to

void LinkedList::move_five_nodes(Node*& ptr1, Node*& ptr2) { ... }

Best Answer

Related Solutions

C++ Pointers – Passing References to Pointers in C++

C++ Pointers – How to Pass a Pointer Variable as a Reference Parameter

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