[2026-06 LWG Motion 1] P4258R0 C++ Standard Library Ready Issues

source/algorithms.tex

@@ -268,10 +268,9 @@
 \item
   a corresponding iterator argument is initialized with \tcode{ranges::begin(r)} and
 \item
-  a corresponding sentinel argument is initialized with \tcode{ranges::end(r)},
-  or \tcode{ranges::next(ranges::\brk{}begin(r), ranges::end(r))}
-  if the type of \tcode{r} models \libconcept{forward_range}
-  and computing \tcode{ranges::next} meets the specified complexity requirements.
+  a corresponding sentinel argument is initialized with
+  \tcode{ranges::begin(r) + N}
+  where \tcode{N} is equal to \tcode{ranges::distance(r)}.
 \end{itemize}
 
 \pnum

source/exec.tex

@@ -4911,7 +4911,7 @@
 \end{codeblock}
 where \tcode{\placeholder{sends-stopped}} equals \tcode{true}
 if and only if there exists an element \tcode{S} of \tcode{Sndrs} such that
-\tcode{completion_signatures_of_t<S, \exposid{when-all-env}<Env>>}
+\tcode{completion_signatures_of_t<S, \exposid{when-all-env}<env_of_t<Rcvr>>>}
 contains \tcode{set_stopped_t()}.
 \end{itemize}
 
@@ -5641,9 +5641,9 @@
 namespace std::execution {
   template<class Alloc, @\libconcept{scope_token}@ Token, @\libconcept{sender}@ Sender, class Env>
   struct @\exposidnc{spawn-future-state}@                                                 // \expos
-    : @\exposid{spawn-future-state-base}@<completion_signatures_of_t<@\exposid{future-spawned-sender}@<Sender, Env>>> {
+    : @\exposid{spawn-future-state-base}@<completion_signatures_of_t<@\exposid{future-spawned-sender}@<Sender, Env>, env<>>> {
     using @\exposidnc{sigs-t}@ =                                                          // \expos
-      completion_signatures_of_t<@\exposid{future-spawned-sender}@<Sender, Env>>;
+      completion_signatures_of_t<@\exposid{future-spawned-sender}@<Sender, Env>, env<>>;
     using @\exposidnc{receiver-t}@ =                                                      // \expos
       @\exposid{spawn-future-receiver}@<@\exposid{sigs-t}@>;
     using @\exposidnc{op-t}@ =                                                            // \expos
@@ -6838,8 +6838,7 @@
 \tcode{(void(\exposid{sndr}), auto(\exposid{rcvr}))} is potentially-throwing.
 \item
 The expression \tcode{get_completion_scheduler<C>(get_env(\exposid{sndr}))}
-is potentially-throwing if and only if \exposid{sndr} is potentially-throwing,
-has type \exposid{run-loop-scheduler}, and
+has type \exposid{run-loop-scheduler} and
 compares equal to the \exposid{run-loop-\newline scheduler} instance
 from which \exposid{sndr} was obtained.
 \end{itemize}
@@ -7161,11 +7160,12 @@
 
 \pnum
 \tcode{as_awaitable} is a customization point object.
-For subexpressions \tcode{expr} and \tcode{p}
-where \tcode{p} is an lvalue,
+For subexpressions \tcode{expr} and \tcode{p},
 \tcode{Expr} names the type \tcode{decltype((expr))} and
 \tcode{Promise} names the type \tcode{decay_t<decltype((p))>},
-\tcode{as_awaitable(expr, p)} is expression-equivalent to,
+\tcode{as_awaitable(expr, p)} is ill-formed if \tcode{p} is not an lvalue,
+otherwise \tcode{as_awaitable(expr, p)} is expression-equivalent to
+the expression specified below,
 except that the evaluations of \tcode{expr} and \tcode{p}
 are indeterminately sequenced:
 \begin{itemize}

source/future.tex

@@ -987,6 +987,13 @@
 T fetch_@\placeholdernc{key}@(T operand, memory_order order = memory_order::seq_cst) volatile noexcept;
 T operator @\placeholdernc{op}@=(T operand) volatile noexcept;
 T* fetch_@\placeholdernc{key}@(ptrdiff_t operand, memory_order order = memory_order::seq_cst) volatile noexcept;
+value_type operator++(int) volatile noexcept;
+value_type operator--(int) volatile noexcept;
+value_type operator++() volatile noexcept;
+value_type operator--() volatile noexcept;
+void wait(T old, memory_order order = memory_order::seq_cst) const volatile noexcept;
+void notify_one() volatile noexcept;
+void notify_all() volatile noexcept;
 \end{codeblock}
 
 \rSec2[depr.atomics.nonmembers]{Non-member functions}

source/iterators.tex

@@ -4339,17 +4339,17 @@
       constexpr auto operator<=>(const I& y) const
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I> &&
                  @\libconcept{three_way_comparable_with}@<Iterator, I>;
-    template<@\exposconcept{not-a-const-iterator}@ I>
-      friend constexpr bool operator<(const I& x, const basic_const_iterator& y)
+    template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+      friend constexpr bool operator<(const I& x, const basic_const_iterator<J>& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-    template<@\exposconcept{not-a-const-iterator}@ I>
-      friend constexpr bool operator>(const I& x, const basic_const_iterator& y)
+    template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+      friend constexpr bool operator>(const I& x, const basic_const_iterator<J>& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-    template<@\exposconcept{not-a-const-iterator}@ I>
-      friend constexpr bool operator<=(const I& x, const basic_const_iterator& y)
+    template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+      friend constexpr bool operator<=(const I& x, const basic_const_iterator<J>& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-    template<@\exposconcept{not-a-const-iterator}@ I>
-      friend constexpr bool operator>=(const I& x, const basic_const_iterator& y)
+    template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+      friend constexpr bool operator>=(const I& x, const basic_const_iterator<J>& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 
     friend constexpr basic_const_iterator operator+(const basic_const_iterator& i,
@@ -4704,17 +4704,17 @@
 \indexlibrarymember{operator<=}{basic_const_iterator}%
 \indexlibrarymember{operator>=}{basic_const_iterator}%
 \begin{itemdecl}
-template<@\exposconcept{not-a-const-iterator}@ I>
-  friend constexpr bool operator<(const I& x, const basic_const_iterator& y)
+template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+  friend constexpr bool operator<(const I& x, const basic_const_iterator<J>& y)
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-template<@\exposconcept{not-a-const-iterator}@ I>
-  friend constexpr bool operator>(const I& x, const basic_const_iterator& y)
+template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+  friend constexpr bool operator>(const I& x, const basic_const_iterator<J>& y)
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-template<@\exposconcept{not-a-const-iterator}@ I>
-  friend constexpr bool operator<=(const I& x, const basic_const_iterator& y)
+template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+  friend constexpr bool operator<=(const I& x, const basic_const_iterator<J>& y)
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-template<@\exposconcept{not-a-const-iterator}@ I>
-  friend constexpr bool operator>=(const I& x, const basic_const_iterator& y)
+template<@\exposconcept{not-a-const-iterator}@ I, @\libconcept{same_as}@<Iterator> J>
+  friend constexpr bool operator>=(const I& x, const basic_const_iterator<J>& y)
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 \end{itemdecl}
 
@@ -4818,7 +4818,7 @@
     using pointer           = Iterator;
     using reference         = iter_rvalue_reference_t<Iterator>;
 
-    constexpr move_iterator();
+    constexpr move_iterator() requires @\libconcept{default_initializable}@<Iterator> = default;
     constexpr explicit move_iterator(Iterator i);
     template<class U> constexpr move_iterator(const move_iterator<U>& u);
     template<class U> constexpr move_iterator& operator=(const move_iterator<U>& u);
@@ -4856,7 +4856,7 @@
           noexcept(noexcept(ranges::iter_swap(x.current, y.current)));
 
   private:
-    Iterator current;   // \expos
+    Iterator current = Iterator();      // \expos
   };
 }
 \end{codeblock}
@@ -4912,18 +4912,6 @@
 
 \rSec3[move.iter.cons]{Construction and assignment}
 
-\indexlibraryctor{move_iterator}%
-\begin{itemdecl}
-constexpr move_iterator();
-\end{itemdecl}
-
-\begin{itemdescr}
-\pnum
-\effects
-Value-initializes \tcode{current}.
-\end{itemdescr}
-
-
 \indexlibraryctor{move_iterator}%
 \begin{itemdecl}
 constexpr explicit move_iterator(Iterator i);
@@ -7274,6 +7262,7 @@
 \item \libheaderref{optional}
 \item \libheaderrefx{regex}{re.syn}
 \item \libheaderrefx{set}{associative.set.syn}
+\item \libheaderref{simd}
 \item \libheaderref{span}
 \item \libheaderref{stacktrace}
 \item \libheaderref{string}

source/ranges.tex

@@ -2390,7 +2390,7 @@
   requires(Container& c, Ref&& ref) {
     requires (requires { c.emplace_back(std::forward<Ref>(ref)); } ||
               requires { c.push_back(std::forward<Ref>(ref)); } ||
-              requires { c.emplace(c.end(), std::forward<Ref>(ref)); } ||
+              requires { c.emplace_hint(c.end(), std::forward<Ref>(ref)); } ||
               requires { c.insert(c.end(), std::forward<Ref>(ref)); });
   };
 \end{codeblock}
@@ -2405,8 +2405,8 @@
       c.emplace_back(std::forward<Ref>(ref));
     else if constexpr (requires { c.push_back(declval<Ref>()); })
       c.push_back(std::forward<Ref>(ref));
-    else if constexpr (requires { c.emplace(c.end(), declval<Ref>()); })
-      c.emplace(c.end(), std::forward<Ref>(ref));
+    else if constexpr (requires { c.emplace_hint(c.end(), declval<Ref>()); })
+      c.emplace_hint(c.end(), std::forward<Ref>(ref));
     else
       c.insert(c.end(), std::forward<Ref>(ref));
   };
@@ -8192,6 +8192,8 @@
     ++@\placeholder{current}@;
     if (@\placeholder{current}@ == end)
       @\exposid{trailing_empty_}@ = true;
+    else if constexpr (!@\libconcept{forward_range}@<V>)
+      @\exposid{trailing_empty_}@ = true;
   }
 }
 else {

source/support.tex

@@ -287,9 +287,11 @@
 The macro
 \indexlibraryglobal{NULL}%
 \tcode{NULL}
-is an \impldef{definition of \tcode{NULL}} null pointer constant.
+is an \impldef{definition of \tcode{NULL}} null pointer constant
+that is a literal\iref{lex.icon,lex.nullptr}.
 \begin{footnote}
 Possible definitions include
+\tcode{nullptr},
 \tcode{0}
 and
 \tcode{0L},
@@ -578,8 +580,8 @@
   // freestanding, also in \libheader{memory}, \libheader{scoped_allocator}, \libheader{string}, \libheader{deque}, \libheader{forward_list}, \libheader{list},
   // \libheader{vector}, \libheader{map}, \libheader{set}, \libheader{unordered_map}, \libheader{unordered_set}
 #define @\defnlibxname{cpp_lib_any}@                               201606L // also in \libheader{any}
-#define @\defnlibxname{cpp_lib_apply}@                             202506L
-  // freestanding, also in \libheader{tuple}, \libheader{type_traits}
+#define @\defnlibxname{cpp_lib_apply}@                             202603L
+  // freestanding, also in \libheader{tuple}, \libheader{type_traits}, \libheader{meta}
 #define @\defnlibxname{cpp_lib_array_constexpr}@                   201811L
   // freestanding, also in \libheader{iterator}, \libheader{array}
 #define @\defnlibxname{cpp_lib_as_const}@                          201510L // freestanding, also in \libheader{utility}
@@ -646,7 +648,7 @@
 #define @\defnlibxname{cpp_lib_constexpr_queue}@                   202502L // also in \libheader{queue}
 #define @\defnlibxname{cpp_lib_constexpr_set}@                     202502L // also in \libheader{set}
 #define @\defnlibxname{cpp_lib_constexpr_stack}@                   202502L // also in \libheader{stack}
-#define @\defnlibxname{cpp_lib_constexpr_string}@                  201907L // also in \libheader{string}
+#define @\defnlibxname{cpp_lib_constexpr_string}@                  202511L // also in \libheader{string}
 #define @\defnlibxname{cpp_lib_constexpr_string_view}@             201811L // also in \libheader{string_view}
 #define @\defnlibxname{cpp_lib_constexpr_tuple}@                   201811L // freestanding, also in \libheader{tuple}
 #define @\defnlibxname{cpp_lib_constexpr_typeinfo}@                202106L // freestanding, also in \libheader{typeinfo}

source/threads.tex

@@ -3012,9 +3012,9 @@
 \end{note}
 
 \pnum
-Atomic read-modify-write operations shall always read the last value
-(in the modification order) written before the write associated with
-the read-modify-write operation.
+An atomic read-modify-write operation always reads the value
+from the side effect that immediately precedes the side effect of the
+read-modify-write operation in the modification order.
 
 \pnum
 An \defnadj{atomic}{modify-write operation} is
@@ -4943,6 +4943,11 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\constraints
+For the \tcode{volatile} overload of this function,
+\tcode{is_always_lock_free} is \tcode{true}.
+
 \pnum
 \expects
 \tcode{order} is
@@ -4979,6 +4984,11 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\constraints
+For the \tcode{volatile} overload of this function,
+\tcode{is_always_lock_free} is \tcode{true}.
+
 \pnum
 \effects
 Unblocks the execution of at least one atomic waiting operation
@@ -5000,6 +5010,11 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\constraints
+For the \tcode{volatile} overload of this function,
+\tcode{is_always_lock_free} is \tcode{true}.
+
 \pnum
 \effects
 Unblocks the execution of all atomic waiting operations
@@ -11534,7 +11549,7 @@
 \begin{itemdescr}
 \pnum
 \effects
-Abandons any shared state\iref{futures.state} and then as if
+Equivalent to
 \tcode{promise(std::move(rhs)).swap(*this)}.
 
 \pnum
@@ -12736,12 +12751,12 @@
 \begin{itemdescr}
 \pnum
 \effects
-\begin{itemize}
-\item
-Releases any shared state\iref{futures.state};
-\item
-calls \tcode{packaged_task(std::move(rhs)).swap(*this)}.
-\end{itemize}
+Equivalent to
+\tcode{packaged_task(std::move(rhs)).swap(*this)}.
+
+\pnum
+\returns
+\tcode{*this}.
 \end{itemdescr}
 
 \indexlibrarydtor{packaged_task}%

source/time.tex

@@ -1015,7 +1015,8 @@
 \tcode{C1::is_steady}  &
   \tcode{const bool}      &
   \tcode{true} if \tcode{t1 <= t2} is always \tcode{true} and the time between clock
-  ticks is constant, otherwise \tcode{false}.  \\ \rowsep
+  ticks is constant, otherwise \tcode{false}.
+  \tcode{C1::is_steady} shall be usable in constant expressions\iref{expr.const}.  \\ \rowsep
 
 \tcode{C1::now()} &
   \tcode{C1::time_point}  &

source/utilities.tex

@@ -2463,7 +2463,8 @@
 
 \pnum
 \effects
-Equivalent to the preceding constructors except that each element is constructed with
+Equivalent to the preceding constructors
+except that each element of non-reference type is constructed with
 uses-allocator construction\iref{allocator.uses.construction}.
 \end{itemdescr}