Question

What is the design factor in managing memory in C++?
For example: why is there a memory leak when a program does not release a memory object before it exits? Isn’t a good programming language design supposed to maintain a “foo-table” that takes care of this situation ? I know I am being a bit naive, but what is the design philosophy of memory management in C++ with respect to classes, structs, methods, interfaces, abstract classes?

Certainly one cannot humanely remember every spec of C++. What is the core driving design of memory management?

Answer 1

What is the core driving design of memory management ?

In almost all cases, you should use automatic resource management. Basically:

• Wherever it is practical to do so, prefer creating objects with automatic storage duration (that is, on the stack, or function-local)
• Whenever you must use dynamic allocation, use Scope-Bound Resource Management (SBRM; more commonly called Resource Acquisition is Initialization or RAII).

Rarely do you have to write your own RAII container: the C++ standard library provides a whole set of containers (e.g., vector and map) and smart pointers like shared_ptr (from C++ TR1, C++0x, and Boost) work very well for most common situations.

Basically, in really good C++ code, you should never call delete yourself¹ to clean up memory that you’ve allocated: memory management and resource cleanup should always be encapsulated in a container of some kind.

^{1. Obviously, the exception here is when you implement an RAII container yourself, since that container must be responsible for cleaning up whatever it owns.}