C++ Language/Indirection/RvalueReferences/MoveSemantics

From Wikibooks, open books for an open world
Jump to navigation Jump to search
C++ Language
  1. Overview
  2. Preprocessing
    1. Macros
    2. Tokenization
    3. Preprocessing Strings
    4. Compile-time Constants
    5. Compile-time Assertions
    6. Conditional-Compilation
  3. Namespace
    1. Namespace Shortcuts
    2. Nesting
    3. Splitting across Files
    4. Named and Unnamed
  4. Type
    1. Hungarian Prefixes
    2. Boolean
    3. Literals
    4. Bitwise Representation
    5. Max Value
    6. Conversion
    7. Enumeration
    8. Shortcuts
    9. Variant
    10. RTTI: RunTime Type Information
  5. Variables
    1. Lifetime and Scope
    2. Initialization
    3. Uniform Initialization
    4. Initialize without Constructor
    5. Decomposing-Auto
    6. Define at Same Time as Type
  6. Indirection
    1. Pointers
    2. Typed NULL
    3. Arrays
    4. Reference Variables
    5. Rvalue-References
    6. Smart Pointers
  7. Expressions
    1. Precedence
    2. Chain of Assignment
  8. Program Flow
    1. Loops
    2. The break Statement
    3. Return Value
    4. Parameters
    5. Function Overloading
    6. Function-Pointer
    7. Deprecating a Function
  9. Objects
    1. Accessibility
    2. Unwanted Compiler-Generated Functions
    3. Constructors
    4. Destructors
    5. Const Members
    6. Static Members
    7. Inheritance
    8. Operator Overloading
    9. Nested Classes
    10. Pointer to Members
    11. Low-Level C Structures
  10. Templates
    1. Templated-Functions
    2. Templated-Classes
    3. Templated-Variables
    4. Template-Parameters
    5. Traits
    6. Metaprogramming
    7. Concepts
  11. Error Handling
    1. Returning an Error Code
    2. Assertions
    3. C++ Exception Handling
  12. Standard Libraries
    1. C-Runtime
    2. STL: Standard Template Library
    3. Strings
    4. IOStreams
    5. Filesystem Access
    6. Multithreading
    7. RNG: Random Number Generator
  13. Obsolete Features

Traditionally, a class could provide a "copy-constructor" CRType::CRType(const CRType& x) {...} and a "copy-assignment operator" CRType& CRType::operator=(const CRType& x) {...}. These would get used in several situations, such as the definition of oDesti by CRType oDesti(oSource); (where oSource had already been defined as a CRType object). If CRType is some kind of custom container, then these two functions are usually implemented by deeply copying all contained items, which might be computationally-expensive.

In modern software, these are supplemented by also programming "move-constructor" and "move-assignment operator" functions that are implemented by only transferring a payload handle. Function overloading can distinguish between move-constructor and copy-constructor, because the move-constructor parameter's type is a "rvalue-reference" CRType&&.

Additional information about move-semantics (includes interactive examples)

Retrieved from "https://en.wikibooks.org/w/index.php?title=C%2B%2B_Language/Indirection/RvalueReferences/MoveSemantics&oldid=4035368"