Why are the terms "automatic" and "dynamic" preferred over the terms "stack" and "heap" in C++ memory management?

c++ heap-memory stack-memory automatic-storage
Luchian Grigore picture Luchian Grigore · Feb 7, 2012 · Viewed 7.1k times · Source

Related to a lot of questions and answers on SO, I've learned that it's better to refer to objects whose lifetime is managed as residing in automatic storage rather than the stack.

Also, dynamically allocated objects shouldn't be referred to as residing on the heap, but in dynamic storage.

I get that there is automatic, dynamic and static storage, but never really understood the difference between automatic-stack and dynamic-heap. Why are the former preferred?

I'm not asking what stack/heap mean or how memory management works. I'm asking why the terms automatic/dynamic storage are preferred over the terms stack/heap.

Answer

Useless picture Useless · Feb 7, 2012

Automatic tells me something about the lifetime of an object: specifically that it is bound automatically to the enclosing scope, and will be destroyed automatically when that scope exits.

Dynamic tells me that the lifetime of an object is not controlled automatically by the compiler, but is under my direct control.

Stack is an overloaded name for a type of container, and for the related popular instruction pointer protocol supported by common call and ret instructions. It doesn't tell me anything about the lifetime of an object, except through a historical association to object lifetimes in C, due to popular stack frame conventions. Note also that in some implementations, thread-local storage is on the stack of a thread, but is not limited to the scope of any single function.

Heap is again an overloaded name, indicating either a type of sorted container or a free-store management system. This is not the only free store available on all systems, and nor does it tell me anything concrete about the lifetime of an object allocated with new.

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