C++: Reasons for passing objects by value

Question

In Java, all variables containing proper objects are actually references (i.e. pointers). Therefore, method calls with these objects as arguments are always \"by reference\"

Answer 1

ALWAYS use pointers when using objects as arguments

No, in C++ always pass by reference, unless your function can be called with nullptr as a valid argument. If the function does not need to modify the argument, pass by const reference.

Passing arguments by value has several uses.

If your function needs to create a copy of the argument it is better to create this copy by passing by value rather than creating a copy within the function. For instance:

void foo( widget const& w )
{
  widget temp( w );
  // do something with temp
}

Instead use

void foo( widget w )  // copy is made here
{
  // operate on w itself
}

Doing this also has the benefit of allowing the compiler to move widget if possible, which is generally more efficient than creating copies.