Merge 2023-11 LWG Motion 13

P2871R3 Remove deprecated <codecvt> header

Author: tkoeppe

source/compatibility.tex

@@ -166,6 +166,29 @@
 The old functionality can be achieved by calling \tcode{shrink_to_fit()} instead,
 or the function call can be safely eliminated with no side effects.
 
+\nodiffref
+\change
+Remove header \libnoheader{codecvt} and all its contents.
+\rationale
+The header has been deprecated for the previous three editions of this standard
+and no longer implements the current Unicode standard, supporting only the
+obsolete UCS-2 encoding.
+Ongoing support is at implementer's discretion,
+exercising freedoms granted by \ref{zombie.names}.
+\effect
+A valid \CppXXIII{} program \tcode{\#include}-ing the header or importing the
+header unit may fail to compile. Code that uses any of the following names by
+importing the standard library modules may fail to compile:
+\begin{itemize}
+\item \tcode{codecvt_mode},
+\item \tcode{codecvt_utf16},
+\item \tcode{codecvt_utf8},
+\item \tcode{codecvt_utf8_utf16},
+\item \tcode{consume_header},
+\item \tcode{generate_header}, and
+\item \tcode{little_endian}.
+\end{itemize}
+
 \rSec1[diff.cpp20]{\Cpp{} and ISO \CppXX{}}
 
 \rSec2[diff.cpp20.general]{General}
@@ -2039,11 +2062,10 @@
 \libheaderref{array},
 \libheaderrefx{atomic}{atomics.syn},
 \libheaderrefx{chrono}{time.syn},
-\libdeprheaderref{codecvt},
 \libheaderrefx{condition_variable}{condition.variable.syn},
 \libheaderrefx{forward_list}{forward.list.syn},
 \libheaderref{future},
-\libheaderrefx{initializer_list}{initializer.list.syn},
+\libheaderrefx{initiali\-zer_list}{initializer.list.syn},
 \libheaderref{mutex},
 \libheaderrefx{random}{rand.synopsis},
 \libheaderref{ratio},

source/future.tex

@@ -2023,129 +2023,6 @@
 Equivalent to: \tcode{return visit(std::forward<Visitor>(vis), arg.value);}
 \end{itemdescr}
 
-\rSec1[depr.locale.stdcvt]{Deprecated standard code conversion facets}
-
-\rSec2[depr.locale.stdcvt.general]{General}
-
-\pnum
-The header \libheaderdef{codecvt} provides
-code conversion facets for various character encodings.
-
-\rSec2[depr.codecvt.syn]{Header \tcode{<codecvt>} synopsis}
-
-\indexlibraryglobal{codecvt_mode}%
-\indexlibraryglobal{codecvt_utf8}%
-\indexlibraryglobal{codecvt_utf16}%
-\indexlibraryglobal{codecvt_utf8_utf16}%
-\begin{codeblock}
-namespace std {
-  enum codecvt_mode {
-    consume_header = 4,
-    generate_header = 2,
-    little_endian = 1
-  };
-
-  template<class Elem, unsigned long Maxcode = 0x10ffff, codecvt_mode Mode = (codecvt_mode)0>
-    class codecvt_utf8 : public codecvt<Elem, char, mbstate_t> {
-    public:
-      explicit codecvt_utf8(size_t refs = 0);
-      ~codecvt_utf8();
-    };
-
-  template<class Elem, unsigned long Maxcode = 0x10ffff, codecvt_mode Mode = (codecvt_mode)0>
-    class codecvt_utf16 : public codecvt<Elem, char, mbstate_t> {
-    public:
-      explicit codecvt_utf16(size_t refs = 0);
-      ~codecvt_utf16();
-    };
-
-  template<class Elem, unsigned long Maxcode = 0x10ffff, codecvt_mode Mode = (codecvt_mode)0>
-    class codecvt_utf8_utf16 : public codecvt<Elem, char, mbstate_t> {
-    public:
-      explicit codecvt_utf8_utf16(size_t refs = 0);
-      ~codecvt_utf8_utf16();
-    };
-}
-\end{codeblock}
-
-\rSec2[depr.locale.stdcvt.req]{Requirements}
-
-\pnum
-For each of the three code conversion facets \tcode{codecvt_utf8},
-\tcode{codecvt_utf16}, and \tcode{codecvt_utf8_utf16}:
-\begin{itemize}
-\item
-  \tcode{Elem} is one of
-  \keyword{wchar_t}, \keyword{char16_t}, or \keyword{char32_t}.
-\item
-  \tcode{Maxcode} is the largest value of \tcode{Elem}
-  converted to \tcode{\keyword{unsigned} \keyword{long}}
-  that the facet
-  will read or write without reporting a conversion error.
-\item
-  If \tcode{(Mode \& consume_header)}, the facet shall consume an
-  initial header sequence, if present, when reading a multibyte sequence
-  to determine the endianness of the subsequent multibyte sequence to be read.
-\item
-  If \tcode{(Mode \& generate_header)}, the facet shall generate an
-  initial header sequence when writing a multibyte sequence to advertise
-  the endianness of the subsequent multibyte sequence to be written.
-\item
-  If \tcode{(Mode \& little_endian)}, the facet shall generate a
-  multibyte sequence in little-endian order,
-  as opposed to the default big-endian order.
-\item
-  UCS-2 is the same encoding as UTF-16,
-  except that it encodes scalar values in the range
-  \ucode{0000}--\ucode{ffff} (Basic Multilingual Plane) only.
-\end{itemize}
-
-\pnum
-\indextext{UTF-8}%
-\indextext{UCS-2}%
-\indextext{UTF-32}%
-For the facet \tcode{codecvt_utf8}\indexlibraryglobal{codecvt_utf8}:
-\begin{itemize}
-\item
-  The facet shall convert between UTF-8 multibyte sequences
-  and UCS-2 or UTF-32 (depending on the size of \tcode{Elem}).
-\item
-  Endianness shall not affect how multibyte sequences are read or written.
-\item
-  The multibyte sequences may be written as either a text or a binary file.
-\end{itemize}
-
-\pnum
-\indextext{UTF-16}%
-\indextext{UCS-2}%
-\indextext{UTF-32}%
-For the facet \tcode{codecvt_utf16}\indexlibraryglobal{codecvt_utf16}:
-\begin{itemize}
-\item
-  The facet shall convert between UTF-16 multibyte sequences
-  and UCS-2 or UTF-32 (depending on the size of \tcode{Elem}).
-\item
-  Multibyte sequences shall be read or written
-  according to the \tcode{Mode} flag, as set out above.
-\item
-  The multibyte sequences may be written only as a binary file.
-  Attempting to write to a text file produces undefined behavior.
-\end{itemize}
-
-\pnum
-\indextext{UTF-8}%
-\indextext{UTF-16}%
-For the facet \tcode{codecvt_utf8_utf16}\indexlibraryglobal{codecvt_utf8_utf16}:
-\begin{itemize}
-\item
-  The facet shall convert between UTF-8 multibyte sequences
-  and UTF-16 (one or two 16-bit codes) within the program.
-\item
-  Endianness shall not affect how multibyte sequences are read or written.
-\item
-  The multibyte sequences may be written as either a text or a binary file.
-\end{itemize}
-
 \rSec1[depr.conversions]{Deprecated convenience conversion interfaces}
 
 \rSec2[depr.conversions.general]{General}
@@ -2174,12 +2051,12 @@
 (like class template \tcode{codecvt}) to perform the conversions, without
 affecting any streams or locales.
 \begin{example}
-If you want to use the code
-conversion facet \tcode{codecvt_utf8} to output to \tcode{cout} a UTF-8
+If you want to use a code
+conversion facet, \tcode{codecvt_for_utf8}, to output to \tcode{cout} a UTF-8
 multibyte sequence corresponding to a wide string, but you don't want to
 alter the locale for \tcode{cout}, you can write something like:
 \begin{codeblock}
-std::wstring_convert<std::codecvt_utf8<wchar_t>> myconv;
+std::wstring_convert<codecvt_for_utf8<wchar_t>> myconv;
 std::string mbstring = myconv.to_bytes(L"Hello\n");
 std::cout << mbstring;
 \end{codeblock}

source/lib-intro.tex

@@ -1126,7 +1126,6 @@
 \tcode{<bitset>} \\
 \tcode{<charconv>} \\
 \tcode{<chrono>} \\
-\tcode{<codecvt>} \\
 \tcode{<compare>} \\
 \tcode{<complex>} \\
 \tcode{<concepts>} \\
@@ -3028,18 +3027,25 @@
 \item \indexlibraryzombie{bind2nd} \tcode{bind2nd},
 \item \indexlibraryzombie{binder1st} \tcode{binder1st},
 \item \indexlibraryzombie{binder2nd} \tcode{binder2nd},
+\item \indexlibraryzombie{codecvt_mode} \tcode{codecvt_mode},
+\item \indexlibraryzombie{codecvt_utf16} \tcode{codecvt_utf16},
+\item \indexlibraryzombie{codecvt_utf8} \tcode{codecvt_utf8},
+\item \indexlibraryzombie{codecvt_utf8_utf16} \tcode{codecvt_utf8_utf16},
 \item \indexlibraryzombie{const_mem_fun1_ref_t} \tcode{const_mem_fun1_ref_t},
 \item \indexlibraryzombie{const_mem_fun1_t} \tcode{const_mem_fun1_t},
 \item \indexlibraryzombie{const_mem_fun_ref_t} \tcode{const_mem_fun_ref_t},
 \item \indexlibraryzombie{const_mem_fun_t} \tcode{const_mem_fun_t},
+\item \indexlibraryzombie{consume_header} \tcode{consume_header},
 \item \indexlibraryzombie{declare_no_pointers} \tcode{declare_no_pointers},
 \item \indexlibraryzombie{declare_reachable} \tcode{declare_reachable},
+\item \indexlibraryzombie{generate_header} \tcode{generate_header},
 \item \indexlibraryzombie{get_pointer_safety} \tcode{get_pointer_safety},
 \item \indexlibraryzombie{get_temporary_buffer} \tcode{get_temporary_buffer},
 \item \indexlibraryzombie{get_unexpected} \tcode{get_unexpected},
 \item \indexlibraryzombie{gets} \tcode{gets},
 \item \indexlibraryzombie{is_literal_type} \tcode{is_literal_type},
 \item \indexlibraryzombie{is_literal_type_v} \tcode{is_literal_type_v},
+\item \indexlibraryzombie{little_endian} \tcode{little_endian},
 \item \indexlibraryzombie{mem_fun1_ref_t} \tcode{mem_fun1_ref_t},
 \item \indexlibraryzombie{mem_fun1_t} \tcode{mem_fun1_t},
 \item \indexlibraryzombie{mem_fun_ref_t} \tcode{mem_fun_ref_t},
@@ -3091,6 +3097,7 @@
 The header names
 \libnoheader{ccomplex},
 \libnoheader{ciso646},
+\libnoheader{codecvt},
 \libnoheader{cstdalign},
 \libnoheader{cstdbool}, and
 \libnoheader{ctgmath}

source/xrefdelta.tex

@@ -22,6 +22,12 @@
 % P2864R2 Remove deprecated arithmetic conversions
 \removedxref{depr.arith.conv.enum}
 
+% P2871R3 Remove deprecated <codecvt> header
+\removedxref{depr.codecvt.syn}
+\removedxref{depr.locale.stdcvt}
+\removedxref{depr.locale.stdcvt.general}
+\removedxref{depr.locale.stdcvt.req}
+
 % P2870R3 Remove deprecated typedef from `std::allocator`
 \removedxref{depr.default.allocator}