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[2026-06 LWG Motion 8] P3154R3 (Deprecating signed character types in iostreams) #9122

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Merged
tkoeppe merged 1 commit into from
Jul 15, 2026
+108 −40
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[2026-06 LWG Motion 8] P3154R3 (Deprecating signed character types in iostreams) #9122

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107 changes: 107 additions & 0 deletions source/future.tex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1058,3 +1058,110 @@
\returns
\tcode{y}.
\end{itemdescr}

\Sec1[depr.istream.extractors]{Deprecated \tcode{signed char} and \tcode{unsigned char} extraction}
\pnum
The header \libheaderref{istream} has the following additions:

\begin{itemdecl}
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char& c);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char& c);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Behaves like a formatted input member
(as described in\iref{istream.formatted.reqmts})
of \tcode{in}.
A character is extracted from \tcode{in},
if one is available, and stored in \tcode{c}.
Otherwise, \tcode{ios_base::failbit} is set
in the input function's local error state
before setstate is called.

\pnum
\returns
\tcode{in}.
\end{itemdescr}

\pnum
\begin{itemdecl}
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char (&s)[N]);
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char (&s)[N]);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Behaves like a formatted input member
(as described in\iref{istream.formatted.reqmts})
of \tcode{in}.
After a sentry object is constructed,
\tcode{operator>>} extracts characters and stores them into \tcode{s}.
If \tcode{width()} is greater than zero,
\tcode{n} is \tcode{min(size_t(width()), N)}.
Otherwise \tcode{n} is \tcode{N}.
\tcode{n} is the maximum number of characters stored.

\pnum
Characters are extracted and stored until any of the following occurs:
\begin{itemize}
\item \tcode{n - 1} characters are stored;
\item end of file occurs on the input sequence;
\item letting \tcode{ct} be \tcode{use_facet<ctype<charT>>(in.getloc())}, \tcode{ct.is(ct.space, s)}
is \tcode{true}.
\end{itemize}

\pnum
\tcode{operator>>} then stores a null byte (\tcode{charT()}) in the next position,
which may be the first position if no characters were extracted.
\tcode{operator>>} then calls \tcode{width(0)}.

\pnum
If the function extracted no characters,
\tcode{ios_bit::failbit} is set in the input function's
local error state before \tcode{setstate} is called.

\pnum
\returns
\tcode{in}.
\end{itemdescr}

\Sec1[depr.ostream.inserters]{Deprecated \tcode{signed char} and \tcode{unsigned char} insertion}
\pnum
The header \libheaderref{ostream} has the following additions:

\pnum
\begin{itemdecl}
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, signed char c);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, unsigned char c);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return out << static_cast<char>(c);}
\end{itemdescr}

\pnum
\begin{itemdecl}
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& out, const signed char* s);
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& out, const unsigned char* s);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return out << reinterpret_cast<const char*>(s);}
\end{itemdescr}
41 changes: 1 addition & 40 deletions source/iostreams.tex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4387,17 +4387,9 @@
// \ref{istream.extractors}, character extraction templates
template<class charT, class traits>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&, charT&);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, unsigned char&);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, signed char&);

template<class charT, class traits, size_t N>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&, charT(&)[N]);
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, unsigned char(&)[N]);
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, signed char(&)[N]);
}
\end{codeblock}

Expand Down Expand Up @@ -4919,10 +4911,6 @@
\begin{itemdecl}
template<class charT, class traits, size_t N>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& in, charT (&s)[N]);
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char (&s)[N]);
template<class traits, size_t N>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char (&s)[N]);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -4976,10 +4964,6 @@
\begin{itemdecl}
template<class charT, class traits>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& in, charT& c);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char& c);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char& c);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -6003,11 +5987,6 @@
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, char);

template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, signed char);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, unsigned char);

template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, wchar_t) = delete;
template<class traits>
Expand All @@ -6033,11 +6012,6 @@
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const char*);

template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const signed char*);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const unsigned char*);

template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>&, const wchar_t*) = delete;
Expand Down Expand Up @@ -6719,11 +6693,6 @@
// specialization
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, char c);
// signed and unsigned
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, signed char c);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, unsigned char c);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -6755,11 +6724,6 @@
basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& out, const char* s);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, const char* s);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, const signed char* s);
template<class traits>
basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out,
const unsigned char* s);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -6790,10 +6754,7 @@
for the overload where the first argument is of type
\tcode{basic_ostream<charT, traits>\&}
and the second is of type
\tcode{const char*},
\item
\tcode{traits::length(reinterpret_cast<const char*>(s))}
for the other two overloads.
\tcode{const char*}.

@jwakely jwakely Jul 15, 2026

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This seems like an incredibly verbose way to say "for the first and third overloads" and "for the second overload". If we want to continue to refer to the parameter types not the ordering, we should at least talk about parameters not arguments!

And maybe the third overload should have been deprecated too, it will be redundant once the deprecated ones are gone.

\end{itemize}
Determines padding for \tcode{seq} as described
in~\ref{ostream.formatted.reqmts}. Inserts \tcode{seq} into
Expand Down
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