DevAcademia lesson/C++ Basics

Dereferencing

Topic progressTopic 63 of 109 - 58% complete

~10 min lesson28 learning blocks5 code examples1 checks/interactions

Lesson outline

What is Dereferencing?

Dereferencing means accessing the value stored at the memory address a pointer holds. It is done using the dereference operator (*).

Key points:

Translates a memory address into the actual value it points to
Can be used for both reading and writing values (unless the pointee type is const)
Dereferencing an invalid pointer (null, dangling, or out-of-bounds) leads to undefined behavior

The * symbol appears in declarations to form pointer types and in expressions to dereference. In expressions, *ptr yields the referred-to object.

Dereferencing is often used to modify values indirectly, to pass values by pointer to functions, and to walk arrays.

Use -> to access members through a pointer to an object. p->m is shorthand for (*p).m.

*, prefix/postfix ++, and + have different precedences. Parentheses make intent explicit.

You cannot modify a value through a pointer-to-const.

void* is a generic, untyped pointer and cannot be dereferenced directly; cast it to the correct type first.

Dereferencing null pointers (nullptr).
Dereferencing dangling pointers (pointing to destroyed or out-of-scope objects).
Dereferencing uninitialized pointers (indeterminate value).
Performing pointer arithmetic that leaves the array's bounds and then dereferencing.
Forgetting parentheses in expressions like (*p)++ vs *p++ (they do different things).

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