What is the lifecycle of a C++ object?

Question

I\'m a seasoned C developer who is just now getting into C++, and I must admit, I\'m very confused about how many ways there are to create, retain, and destroy C++ objects. In C

Answer 1

This is a fairly broad question, but I'll give you a starting point.

What's known in C as a "stack variable" is also called an object with "automatic storage". The lifetime of an object with automatic storage is fairly easy to understand: it's created when control reaches the point it's defined, and then destroyed when it goes out of scope:

int main() {
  int foo = 5; // creation of automatic storage
  do_stuff();
  foo = 1;

  // end of function; foo is destroyed.
}

Now, a thing to note is that = 5 is considered part of the initialization syntax, while = 1 is considered an assignment operation. I don't want you to get confused by = being used for two different things in the language's grammar.

Anyway, C++ takes automatic storage a bit further and allows arbitrary code to be run during the creation and destruction of that object: the constructors and destructors. This gives rise to the wonderful idiom called RAII, which you should use whenever possible. With RAII, resource management becomes automatic.

what are all these things like shared_ptr, weak_ptr, etc.?

Good examples of RAII. They allow you to treat a dynamic resource (malloc/free calls) as an automatic storage object!

Most importantly, when is it correct to copy/assign/whatever = is in C++, and when do you want to use pointers? In C, I got very used to throwing pointers around a lot, because pointer assignment is cheap but struct copying is less so. How do C++'s copy semantics affect this?

const references everywhere, especially for function parameters. const refs avoid copies and prevent modification of the object. If you can't use const ref, chances are a normal reference is suitable. If for some reason you want to reset the reference or set it to null, use a pointer.

What are all the ways to create a C++ object? Direct/copy constructor, assignment, etc. How do they work?

In short, all constructors create objects. Assignment doesn't. Read a book for this.