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P0487R1 Fixing operator>>(basic_istream&, CharT*) (LWG 2499) #2459

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Nov 26, 2018
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P0487R1 Fixing operator>>(basic_istream&, CharT*) (LWG 2499) #2459

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P0487R1 Fixing operator>>(basic_istream&, CharT*) (LWG 2499)
zygoloid Nov 26, 2018
6260a04
[diff.cpp17.input.output] Add ill-formed comment and a still well-for…
Nov 23, 2018
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13 changes: 13 additions & 0 deletions source/compatibility.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -2079,6 +2079,19 @@

\rSec2[diff.cpp17.input.output]{\ref{input.output}: input/output library}

\diffref{istream.extractors}
\change
Character array extraction only takes array types.
\rationale Increase safety via preventing buffer overflow at compile time.
\effect
Valid \CppXVII{} code may fail to compile in this International Standard:
\begin{codeblock}
auto p = new char[100];
char q[100];
std::cin >> std::setw(20) >> p; // ill-formed; previously well-formed
std::cin >> std::setw(20) >> q; // OK
\end{codeblock}

\diffref{ostream.inserters.character}
\change
Overload resolution for ostream inserters used with UTF-8 literals.
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33 changes: 14 additions & 19 deletions source/iostreams.tex
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Expand Up @@ -4270,12 +4270,12 @@
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, signed char&);

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 @@ -4756,12 +4756,12 @@

\indexlibrarymember{operator>>}{basic_istream}%
\begin{itemdecl}
template<class charT, class traits>
basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& in, charT* s);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char* s);
template<class traits>
basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char* s);
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 All @@ -4774,17 +4774,12 @@
object is constructed,
\tcode{operator>>}
extracts characters and stores them into
successive locations of an array whose first element is designated by
\tcode{s}.
If
\tcode{width()}
is greater than zero, \tcode{n} is
\tcode{width()}.
Otherwise \tcode{n} is the number of elements
of the largest array of
\tcode{char_type}
that can store a terminating
\tcode{charT()}.
\tcode{min(size_t(width()), N)}.
Otherwise \tcode{n} is \tcode{N}.
\tcode{n} is the maximum number of characters stored.

\pnum
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