[Cpp-Programming] Re: newbie q: difference between operator= and copy constructor?

If I want to pass a class defined using new in one function as a reference to another function, the class becomes corrupt.  Maybe the wrong address is passed.  Or maybe the class is out-of-scope.  When I pass a class as a reference to a function, is there anything I need to know?  I've been able to narrow the bug with my program down to a function call: before the.call, everything work fine,  Within the called function, the class becomes unreadable and member function calls return garbage.

On Tuesday, January 8, 2013 9:08:48 AM UTC-5, Harry Potter wrote:

Thank you for your help.  I'll look at the site later.  BTW, it seems that, when I pass a class with a char* (I used the new declarator to define a class) and a function to return a modified version of the char* to another function, the member function returns corrupt information for the char*.

On Tuesday, January 8, 2013 3:58:02 AM UTC-5, Beyeler Studios wrote:

Hi Harry!

Have a look at this tutorial here: http://www.learncpp.com/cpp-tutorial/911-the-copy-constructor-and-overloading-the-assignment-operator/

The signatures are:

T(const T& o); // copy constructor

T& operator= (const T& o); // assignment operator

Most notable compiler behaviours are:

T a; // calls default constructor

a = someT; // calls assignment operator

T b(someT); // calls copy constructor

T c = someT; // calls copy constructor, too!

Note: the default behaviour for both copy ctor and assign operator is equal to a memcpy (shallow copy). When you overload one or both in your class, they can basically do whatever. Though it's usually a good idea to either completely emulate the copy & assignment behaviour of basic types (deep copy: no shared memory between objects) or use a different approach to accomplish anything more complex as your code gets very hard to debug when assigning and copying don't behave as expected.

Best,

BeyelerStudios

On Monday, 7 January 2013 20:42:10 UTC+1, Harry Potter wrote:

I think the answer to this may solve my previous post: What is the difference between an overloaded = operator and a copy constructor?  How do they behave in ISO C++?

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