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Move special member function

As explained in Learn C++ by Example

A move special member function is a move constructor or move assignment operator that transfers resources from another object.

A move special member function is a move constructor or move assignment operator that transfers resources from another object. Moving can avoid copies, but a move request may perform a copy when the type is not move-enabled. section 6.1.4

Keep these language rules in mind:

  • A user-declared destructor prevents C++ from generating move operations implicitly. section 6.1.4
  • Declaring the move constructor and move assignment operator as =default restores defaulted moves; deleting or declaring one special member can affect the others. section 6.1.4
  • The rule of five recommends deliberately declaring or deleting all five special members when resource ownership requires it; the rule of zero accepts suitable defaults. section 6.1.4

Checking a resource-owning Blob

Type traits can test whether Blob accepts rvalues, but is_move_constructible and is_move_assignable do not prove that a move constructor or move assignment operator exists. They may report true when copying through a const lvalue reference is possible. Static assertions can expose that Blob is neither copyable nor movable. section 6.1.4

How Learn C++ by Example covers it

How deep it goes
Explains implicit-generation rules, defaulting, deletion, and trait limitations, but stops short of implementing a resource transfer.
Examples
Uses a resource-owning Blob, static assertions, type traits, and vector push_back overloads to reveal move behavior.
What it assumes
Assumes special-member and rvalue-reference terminology while clarifying how traits interpret construction and assignment from rvalues.
What you can do after
Diagnose/debug with type traits whether a class is movable, and restore default moves when a destructor suppresses implicit generation.
How it connects
Connects move constructors, move assignment operators, destructors, copy operations, rvalue references, type traits, and the rule of five.
Cover of Learn C++ by Example
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