Merge 2021-10 LWG Motion 1

P2450R0 C++ Standard Library Issues to be moved in Virtual Plenary, Oct. 2021

Author: tkoeppe

source/algorithms.tex

@@ -3939,17 +3939,24 @@
 
 \pnum
 \complexity
-If the types of \tcode{first1}, \tcode{last1}, \tcode{first2}, and \tcode{last2}:
+If
 \begin{itemize}
 \item
+  the types of \tcode{first1}, \tcode{last1}, \tcode{first2}, and \tcode{last2}
   meet the
   \oldconcept{RandomAccessIterator} requirements\iref{random.access.iterators}
+  and \tcode{last1 - first1 != last2 - first2}
   for the overloads in namespace \tcode{std};
 \item
-  pairwise model \libconcept{sized_sentinel_for}\iref{iterator.concept.sizedsentinel}
-  for the overloads in namespace \tcode{ranges},
+ the types of \tcode{first1}, \tcode{last1}, \tcode{first2}, and \tcode{last2}
+ pairwise model \libconcept{sized_sentinel_for}\iref{iterator.concept.sizedsentinel}
+  and \tcode{last1 - first1 != last2 - first2}
+  for the first overload in namespace \tcode{ranges},
+\item
+   \tcode{R1} and \tcode{R2} each model \libconcept{sized_range} and
+   \tcode{ranges::distance(r1) != ranges::distance(r2)}
+   for the second overload in namespace \tcode{ranges},
 \end{itemize}
-and \tcode{last1 - first1 != last2 - first2},
 then no applications of the corresponding predicate and each projection;
 otherwise,
 \begin{itemize}
@@ -4054,9 +4061,17 @@
 \complexity
 No applications of the corresponding predicate and projections if:
 \begin{itemize}
+\item
+for the first overload,
+\begin{itemize}
 \item \tcode{S1} and \tcode{I1} model \tcode{\libconcept{sized_sentinel_for}<S1, I1>},
 \item \tcode{S2} and \tcode{I2} model \tcode{\libconcept{sized_sentinel_for}<S2, I2>}, and
-\item \tcode{last1 - first1 != last2 - first2}.
+\item \tcode{last1 - first1 != last2 - first2};
+\end{itemize}
+\item
+for the second overload,
+\tcode{R1} and \tcode{R2} each model \libconcept{sized_range}, and
+\tcode{ranges::distance(r1) != ranges::distance(r2)}.
 \end{itemize}
 Otherwise, exactly \tcode{last1 - first1} applications
 of the corresponding predicate and projections

source/compatibility.tex

@@ -1773,6 +1773,16 @@
 binary representation of the required template specializations of
 \tcode{std::complex} may not be compatible with this revision of \Cpp{}.
 
+\rSec2[diff.cpp03.locale]{\ref{localization}: localization library}
+
+\diffref{facet.num.get.virtuals}
+\change
+The \tcode{num_get} facet recognizes hexadecimal floating point values.
+\rationale
+Required by new feature.
+\effect
+Valid \CppIII{} code may have different behavior in this revision of \Cpp{}.
+
 \rSec2[diff.cpp03.input.output]{\ref{input.output}: input/output library}
 
 \diffref{istream.sentry,ostream.sentry,iostate.flags}

source/concepts.tex

@@ -346,8 +346,8 @@
 template<class From, class To>
   concept @\deflibconcept{convertible_to}@ =
     is_convertible_v<From, To> &&
-    requires(add_rvalue_reference_t<From> (&f)()) {
-      static_cast<To>(f());
+    requires {
+      static_cast<To>(declval<From>());
     };
 \end{itemdecl}
 

source/iostreams.tex

@@ -6892,7 +6892,10 @@
 Then, if \tcode{os.rdbuf()} is a
 \tcode{basic_syncbuf<charT, traits, Allocator>*},
 called \tcode{buf} for the purpose of exposition,
-calls \tcode{buf->emit()}.
+behaves as an unformatted output function\iref{ostream.unformatted}
+of \tcode{os}.
+After constructing a \tcode{sentry} object, calls \tcode{buf->emit()}.
+If that call returns \tcode{false}, calls \tcode{os.setstate(ios_base::badbit)}.
 
 \pnum
 \returns
@@ -11913,7 +11916,7 @@
 
 \indexlibrarymember{operator=}{basic_syncbuf}%
 \begin{itemdecl}
-basic_syncbuf& operator=(basic_syncbuf&& rhs) noexcept;
+basic_syncbuf& operator=(basic_syncbuf&& rhs);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -11951,7 +11954,7 @@
 
 \indexlibrarymember{swap}{basic_syncbuf}%
 \begin{itemdecl}
-void swap(basic_syncbuf& other) noexcept;
+void swap(basic_syncbuf& other);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -12079,7 +12082,7 @@
 \begin{itemdecl}
 template<class charT, class traits, class Allocator>
   void swap(basic_syncbuf<charT, traits, Allocator>& a,
-            basic_syncbuf<charT, traits, Allocator>& b) noexcept;
+            basic_syncbuf<charT, traits, Allocator>& b);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -12215,7 +12218,8 @@
 \begin{itemdescr}
 \pnum
 \effects
-Calls \tcode{sb.emit()}.
+Behaves as an unformatted output function\iref{ostream.unformatted}.
+After constructing a sentry object, calls \tcode{sb.emit()}.
 If that call returns \tcode{false},
 calls \tcode{setstate(ios_base::badbit)}.
 
@@ -12468,14 +12472,14 @@
 
   // \ref{fs.dir.itr.nonmembers}, range access for directory iterators
   directory_iterator begin(directory_iterator iter) noexcept;
-  directory_iterator end(const directory_iterator&) noexcept;
+  directory_iterator end(directory_iterator) noexcept;
 
   // \ref{fs.class.rec.dir.itr}, recursive directory iterators
   class recursive_directory_iterator;
 
   // \ref{fs.rec.dir.itr.nonmembers}, range access for recursive directory iterators
   recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
-  recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
+  recursive_directory_iterator end(recursive_directory_iterator) noexcept;
 
   // \ref{fs.class.file.status}, file status
   class file_status;
@@ -12645,6 +12649,18 @@
   path weakly_canonical(const path& p);
   path weakly_canonical(const path& p, error_code& ec);
 }
+
+namespace std::ranges {
+  template<>
+    inline constexpr bool enable_borrowed_range<filesystem::directory_iterator> = true;
+  template<>
+    inline constexpr bool enable_borrowed_range<filesystem::recursive_directory_iterator> = true;
+
+  template<>
+    inline constexpr bool enable_view<filesystem::directory_iterator> = true;
+  template<>
+    inline constexpr bool enable_view<filesystem::recursive_directory_iterator> = true;
+}
 \end{codeblock}
 
 \pnum
@@ -15774,7 +15790,7 @@
 
 \indexlibrarymember{end}{directory_iterator}%
 \begin{itemdecl}
-directory_iterator end(const directory_iterator&) noexcept;
+directory_iterator end(directory_iterator) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -16145,7 +16161,7 @@
 
 \indexlibrarymember{end}{recursive_directory_iterator}%
 \begin{itemdecl}
-recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
+recursive_directory_iterator end(recursive_directory_iterator) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}