Memory and Objects
An object is a region of storage, having a type and a value. Every variable is an object.
Every object requires storage in memory.
The process of requesting memory storage is called allocation.
When the object is done being useful, it can be cleaned up and memory freed for use by other objects, that is called deallocation
storage duration of an object is the time between allocation and deallocation of that object.
lifetime of an object begins when the constructor is called, and ends when the destructor is called. (Bound by storage duration)
Automatic objects & storage duration
An automatic object is allocated at the beginning of a code block and deallocated at the end of the code block
The start and end of a given code block is the scope of an automatic object.
Automatic objects have automatic storage durations -- storage duration is handled by way of scope, no extra handling necessary.
Automatic objects are deallocated just before the return has been invoked or the function has concluded.
Automatic objects are also more commonly known as local variables
Static objects & storage duration
A static object is declared at global scope (same level as functions).
Static objects have static storage duration, they are allocated when the program starts, and deallocated when program ends. They can be accessed from any function in the program
Warning
Static globally accessible objects are dangerous. By default, a static variable is accessible from everywhere but is also mutable. This can lead to unexpected behavior if the variable is modified in multiple places and is not considered good practice. If you are using static objects, make sure to make them immutable via const keyword
Static objects are declared with static or extern keywords.
When you use the static keyword, an internal linkage is specified, meaning that this static variable is not accessible to other translation units.
When you use the extern keyword, an external linkage is specified, meaning that this static variable is accessible to other translation units.
Local static objects
A local variant of the global static object. The lifetime of a local static object begins at enclosing function invokation and ends when the program exits.
Static members
Static members are members of a class that are not associated with any given instance of that class, but are namespaced to that class. They have static storage duration for the duration of the program.