• 1Syntax
• 2Explanation
• 3Notes
  • 3.1Automatic move from local variables and parameters
  • 3.2Guaranteed copy elision
• 4Keywords
• 5Example
• 6Defect reports
• 7See also

There is asequence point between the copy-initialization of the result of the function call and the destruction of all temporaries at the end ofexpression.

The copy-initialization of the result of the function call issequenced-before the destruction of all temporaries at the end ofexpression, which, in turn, issequenced-before the destruction of local variables of the block enclosing thereturn statement.

If the return type of the function is a reference type and areturn statement(1,2) binds the returned reference to the result of atemporary expression, the program is ill-formed.

If the return type of a function is specified as aplaceholder type, it will bededuced from the return value. Ifdecltype(auto) is used, the type deduction treats anexpression that can be anentity as anentity.

Automatic move from local variables and parameters

Theexpression ismove-eligible if it is a (possibly parenthesized)identifier expression that names a variable of automatic storage duration whose type is

• a non-volatile object type

• or a non-volatile rvalue reference to object type

and that variable is declared

• in the body
• or as a parameter

of the innermost enclosing function or lambda expression.

If theexpression is move-eligible,overload resolution to select the constructor to use for initialization of the returned value or, forco_return, to select the overload ofpromise.return_value()(since C++20) is performedtwice :

• first as ifexpression were an rvalue expression (thus it may select themove constructor), and

• if the first overload resolution failed

• or it succeeded, but did not select themove constructor (formally, the first parameter of the selected constructor was not an rvalue reference to the (possibly cv-qualified) type ofexpression)

• then overload resolution is performed as usual, withexpression considered as an lvalue (so it may select thecopy constructor).

If theexpression is move-eligible, it is treated as an xvalue (thus overload resolution may select themove constructor).

Guaranteed copy elision

Ifexpression is a prvalue, the result object is initialized directly by that expression. This does not involve a copy or move constructor when the types match (seecopy elision).