std::reference_wrapper::reference_wrapper (3) Linux Manual Page

std::reference_wrapper<T>::reference_wrapper – std::reference_wrapper<T>::reference_wrapper

Synopsis

template< class U > (1)
reference_wrapper( U&& x ) noexcept(/*see below*/) ;
reference_wrapper( const reference_wrapper& other ) noexcept; (2)

Constructs a new reference wrapper.

1) Converts x to T& as if by T& t = std::forward<U>(x);
, then stores a reference to t.This overload only participates in overload resolution if typename std::decay<U>::type is not the same type as reference_wrapper and the expression FUN(std::declval<U>()) is well - formed, where FUN names the set of imaginary functions void FUN(T &) noexcept;

void FUN(T &&) = delete;

2) Copy constructor. Stores a reference to other.get().

Parameters

x – an object to wrap
other – another reference wrapper

Exceptions

1)
noexcept specification:
noexcept(noexcept(FUN(std::declval<U>())))
where FUN is the set of imaginary functions described in the description above.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG_2993 C++11 deleted reference_wrapper(T&&) constructor interferes with overload resolution in some cases replaced with a constructor template