P1643R1 Add wait/notify to atomic_ref<T>

Author: jensmaurer

source/atomics.tex

@@ -663,8 +663,9 @@
 \begin{itemize}
 \item \tcode{atomic<T>::wait},
 \item \tcode{atomic_flag::wait},
-\item \tcode{atomic_wait} and \tcode{atomic_wait_explicit}, and
-\item \tcode{atomic_flag_wait} and \tcode{atomic_flag_wait_explicit}.
+\item \tcode{atomic_wait} and \tcode{atomic_wait_explicit},
+\item \tcode{atomic_flag_wait} and \tcode{atomic_flag_wait_explicit}, and
+\item \tcode{atomic_ref<T>::wait}.
 \end{itemize}
 \end{note}
 
@@ -674,8 +675,9 @@
 \begin{itemize}
 \item \tcode{atomic<T>::notify_one} and \tcode{atomic<T>::notify_all},
 \item \tcode{atomic_flag::notify_one} and \tcode{atomic_flag::notify_all},
-\item \tcode{atomic_notify_one} and \tcode{atomic_notify_all}, and
-\item \tcode{atomic_flag_notify_one} and \tcode{atomic_flag_notify_all}.
+\item \tcode{atomic_notify_one} and \tcode{atomic_notify_all},
+\item \tcode{atomic_flag_notify_one} and \tcode{atomic_flag_notify_all}, and
+\item \tcode{atomic_ref<T>::notify_one} and \tcode{atomic_ref<T>::notify_all}.
 \end{itemize}
 \end{note}
 
@@ -724,6 +726,9 @@
                                memory_order = memory_order_seq_cst) const noexcept;
     bool compare_exchange_strong(T&, T,
                                  memory_order = memory_order_seq_cst) const noexcept;
+    void wait(T, memory_order = memory_order::seq_cst) const noexcept;
+    void notify_one() noexcept;
+    void notify_all() noexcept;
   };
 }
 \end{codeblock}
@@ -1017,6 +1022,72 @@
 \end{note}
 \end{itemdescr}
 
+\indexlibrarymember{wait}{atomic_ref<T>}%
+\begin{itemdecl}
+void wait(T old, memory_order order = memory_order::seq_cst) const noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+\tcode{order} is
+neither \tcode{memory_order::release} nor \tcode{memory_order::acq_rel}.
+
+\pnum
+\effects
+Repeatedly performs the following steps, in order:
+\begin{itemize}
+\item
+  Evaluates \tcode{load(order)} and
+  compares its value representation for equality against that of \tcode{old}.
+\item
+  If they compare unequal, returns.
+\item
+  Blocks until it
+  is unblocked by an atomic notifying operation or is unblocked spuriously.
+\end{itemize}
+
+\pnum
+\remarks
+This function is an atomic waiting operation\iref{atomics.wait}
+on atomic object \tcode{*ptr}.
+\end{itemdescr}
+
+\indexlibrarymember{notify_one}{atomic_ref<T>}%
+\begin{itemdecl}
+void notify_one() noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+Unblocks the execution of at least one atomic waiting operation on \tcode{*ptr}
+that is eligible to be unblocked\iref{atomics.wait} by this call,
+if any such atomic waiting operations exist.
+
+\pnum
+\remarks
+This function is an atomic notifying operation\iref{atomics.wait}
+on atomic object \tcode{*ptr}.
+\end{itemdescr}
+
+\indexlibrarymember{notify_all}{atomic_ref<T>}%
+\begin{itemdecl}
+void notify_all() noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+Unblocks the execution of all atomic waiting operations on \tcode{*ptr}
+that are eligible to be unblocked\iref{atomics.wait} by this call.
+
+\pnum
+\remarks
+ This function is an atomic notifying operation\iref{atomics.wait}
+ on atomic object \tcode{*ptr}.
+\end{itemdescr}
+
 \rSec2[atomics.ref.int]{Specializations for integral types}
 
 \pnum
@@ -1079,6 +1150,10 @@
     bool compare_exchange_strong(@\placeholder{integral}@&, @\placeholder{integral}@,
                                  memory_order = memory_order_seq_cst) const noexcept;
 
+    void wait(integral, memory_order = memory_order::seq_cst) const noexcept;
+    void notify_one() noexcept;
+    void notify_all() noexcept;
+
     @\placeholdernc{integral}@ fetch_add(@\placeholdernc{integral}@,
                        memory_order = memory_order_seq_cst) const noexcept;
     @\placeholdernc{integral}@ fetch_sub(@\placeholdernc{integral}@,
@@ -1206,6 +1281,10 @@
     bool compare_exchange_strong(@\placeholder{floating-point}@&, @\placeholder{floating-point}@,
                                  memory_order = memory_order_seq_cst) const noexcept;
 
+    void wait(@\placeholdernc{floating-point}@, memory_order = memory_order::seq_cst) const noexcept;
+    void notify_one() noexcept;
+    void notify_all() noexcept;
+
     @\placeholder{floating-point}@ fetch_add(@\placeholder{floating-point}@,
                              memory_order = memory_order_seq_cst) const noexcept;
     @\placeholder{floating-point}@ fetch_sub(@\placeholder{floating-point}@,
@@ -1303,6 +1382,10 @@
     bool compare_exchange_strong(T*&, T*,
                                  memory_order = memory_order_seq_cst) const noexcept;
 
+    void wait(T*, memory_order = memory_order::seq_cst) const noexcept;
+    void notify_one() noexcept;
+    void notify_all() noexcept;
+
     T* fetch_add(difference_type, memory_order = memory_order_seq_cst) const noexcept;
     T* fetch_sub(difference_type, memory_order = memory_order_seq_cst) const noexcept;