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Proposed resolution for core issues 411, 1656, and 2333; numeric and universal
character escapes in character and string literals
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<table id="header">
  <tr>
    <th>Document Number:</th>
    <td>P2029R1</td>
  </tr>
  <tr>
    <th>Date:</th>
    <td>2020-02-28</td>
  </tr>
  <tr>
    <th>Audience:</th>
    <td>CWG</td>
  </tr>
  <tr>
    <th>Reply-to:</th>
    <td>Tom Honermann &lt;tom@honermann.net&gt;</td>
  </tr>
</table>


<h1>
Proposed resolution for core issues 411, 1656, and 2333; numeric and universal
character escapes in character and string literals
</h1>


<ul>
  <li><a href="#introduction">Introduction</a></li>
  <li><a href="#changes">Changes from P2029R0</a></li>
  <li><a href="#proposed">Proposed resolution overview</a></li>
  <li>
    <a href="#impact">Implementation impact</>
    <ul>
      <li><a href="#impact-escapes">Semantics of numeric-escape-sequences in UTF-8 literals</a></li>
      <li><a href="#impact-badchar">Character literal type for characters not representable in the execution character set</a></li>
    </ul>
  </li>
  <li><a href="#ack">Acknowledgements</a></li>
  <li>
    <a href="#pr">Proposed resolution</a>
    <ul>
      <li><a href="#lex.phases">[lex.phases]</a></li>
      <li><a href="#lex.ccon">[lex.ccon]</a></li>
      <li><a href="#lex.string">[lex.string]</a></li>
    </ul>
  </li>
</ul>


<h1 id="introduction">Introduction</h1>

<p>
This paper proposes substantial changes to
<a href="http://eel.is/c++draft/lex.phases">[lex.phases]</a>,
<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>, and
<a href="http://eel.is/c++draft/lex.string">[lex.string]</a>
intended to address the following core issues as well as several other
more minor issues.
</p>

<ul>
  <li>
    <a href="http://wg21.link/cwg411">Core Issue 411: Use of universal-character-name in character versus string literals</a><br/>
  </li>
  <li>
    <a href="http://wg21.link/cwg1656">Core Issue 1656: Encoding of numerically-escaped characters</a><br/>
  </li>
  <li>
    <a href="http://wg21.link/cwg2333">Core Issue 2333: Escape sequences in UTF-8 character literals</a>
  </li>
</ul>

<p>
This paper follows a prior
<a href="http://wiki.edg.com/pub/Wg21kona2019/CoreWorkingGroup/cwg2333.html">proposed resolution</a>
that only attempted to address
<a href="http://wg21.link/cwg2333">CWG 2333</a>.
That proposed resolution was
<a href="https://lists.isocpp.org/core/2019/01/5395.php">discussed on the core mailing list</a>
and at the
<a href="http://wiki.edg.com/bin/view/Wg21cologne2019/CoreIssuesProcessingTeleconference2019-06-24">June 24th, 2019 core issues processing teleconference</a>.
The resolution proposed in this paper attempts to address the feedback
provided during those discussions.
</p>

<p>
The notes for <a href="http://wg21.link/cwg2333">CWG 2333</a> in the current
active issues list (revision 100) state that discussion at the
<a href="http://wiki.edg.com/bin/view/Wg21albuquerque/IssuesTeleconference2017-08-14">
August 14th, 2017 core issues processing teleconference</a> resulted in a
determination that numeric escape sequences in UTF-8 character literals
should be ill-formed.  The issue has remained in drafting status since then.
</p>

<p>
SG16 discussed this issue during its
<a href="https://github.com/sg16-unicode/sg16-meetings#october-17th-2018">October 17th, 2018 teleconference</a>.
The SG16 consensus was for a different resolution than is currently described
in the active issues list.  The SG16 consensus was based on the following
observations:
<ul>
  <li>The current resolution in the active issues list contradicts existing
      practice.  gcc, Clang, and Visual C++ all allow octal and hexadecimal
      escape sequences in UTF-8 literals.</li>
  <li>Octal and hexadecimal escape sequences in UTF-8 literals are useful for
      a number of purposes:
    <ul>
      <li>Embedding null characters: <tt>u8"\0"</tt></li>
      <li>Creating ill-formed code unit sequences for testing purposes.</li>
      <li>Creating Modified UTF-8, CESU-8, and WTF-8 string literals.  This
          entails two abilities:
        <ul>
          <li>Embedding <tt>U+0000</tt> as an overlong UTF-8 sequence:
              <tt>u8"\xC0\x80"</tt></li>
          <li>Embedding lone surrogate code points as individual UTF-8 code
              unit sequences.  For example, encoding <tt>U+D800</tt> as
              <tt>u8"\xED\xA0\x80"</tt>.  (Note that use of <tt>\u</tt> escapes
              specifying surrogate code points is ill-formed).</li>
        </ul>
      </li>
      <li>Compatibility with existing log/debug systems that output literals
          with non-printable characters represented with escapes so as to
          facilitate copy/paste of such output into code.</li>
    </ul>
  </li>
</ul>
SG16 conducted the following poll:
<div style="margin-left: 1em;">
Continue to allow hex and octal escapes that indicate code unit values,
requiring only that they fit into the range of the code unit type?
<table border="1">
  <tr>
    <th>SF</th>
    <th>F</th>
    <th>N</th>
    <th>A</th>
    <th>SA</th>
  </tr>
  <tr>
    <td>8</td>
    <td>1</td>
    <td>0</td>
    <td>0</td>
    <td>0</td>
  </tr>
</table>
</div>
In the polled question, "Continue" refers to existing implementation behavior;
to maintain the current implementation status quo exhibited by gcc, Clang and
Visual C++.
</p>

<p>
The proposed resolution reflects the SG16 consensus.
</p>

<p>
<a href="http://wg21.link/cwg411">CWG 411</a> is addressed by specifying
different behavior for character literals vs string literals for characters
that are not representable by a single code unit.  For example, when the
execution character set is UTF-8, <tt>'\u0153'</tt> is conditionally-supported,
has type <tt>int</tt> and an implementation-defined value, but
<tt>"\u0153"</tt> is a character array of length 3 containing the
UTF-8 encoding of U+0153 (LATIN SMALL LIGATURE OE) and a null character
(<tt>\xC5\x93\x00</tt>).
</p>

<p>
<a href="http://wg21.link/cwg1656">CWG 1656</a> is addressed by clarifying
that numeric escape sequences denote code unit values in the execution
character set; that the values are not subject to conversion from the
encoding of the source file to the execution character set.
</p>


<h1 id="changes">Changes from <a href="https://wg21.link/p2029r0">P2029R0</a></h1>

<p>
<ul>
  <li>Addressed core wording review provided at the
      <a href="http://wiki.edg.com/bin/view/Wg21prague/IssuesProcessingTeleconference2020-01-16">January 16th, 2020 core issues processing teleconference</a>.
    <ul>
      <li>[lex.phases]p5: Reworded and made portions of the wording
          a non-normative note.</li>
      <li>[lex.ccon]: Added new
          <tt>character-escape-sequence</tt> and
          <tt>simple-escape-sequence-char</tt>
          grammar productions to simplify wording.</li>
      <li>[lex.ccon]: Added new
          <tt>conditional-escape-sequence</tt> and
          <tt>conditional-escape-sequence-char</tt>
          grammar productions to address previously missing grammar support
          for conditionally-supported implementation-defined escape
          sequences.</li>
      <li>[lex.ccon]: Added new <tt>conditional character literal</tt>,
          <tt>multicharacter literal</tt>,
          <tt>conditional wide character literal</tt>, and
          <tt>wide multicharacter literal</tt>
          character literal kinds to simplify wording.</li>
      <li>[lex.ccon]: Modified wide multicharacter literals to be
          conditionally supported.</li>
      <li>[lex.ccon]: Modified wide character literals for which the
          <tt>c-char-sequence</tt> specifies a character that lacks
          representation in the execution wide-character set or that cannot
          be encoded in a single code unit to be conditionally supported.</li>
      <li>[lex.ccon]p1: Restored original wording and added a drafting note
          that this paragraph will be editorially deleted and all occurrences
          of "character literal" replaced with references to the
          <tt><em>character-literal</em></tt> grammar production.</li>
      <li>[lex.ccon]p2-p6: Replaced these paragraphs with a table that defines
          the kinds of character literals and their properties.</li>
      <li>[lex.ccon]p7: Integrated wording for conditionally-supported
          implementation-defined escape sequences into this paragraph;
          this content was previously in a new paragraph.</li>
      <li>[lex.ccon]p7: Removed the incorrect note about NL, HT, VT, and FF
          potentially lacking representation in the execution character set
          and the execution wide-character set.  The note was added following
          a misreading of [lex.phases].</li>
      <li>[lex.ccon]p7: Removed the note about UTF encodings being able to
          represent all simple-escape-sequences using a single code unit.</li>
      <li>[lex.ccon]p7: Moved the contents of footnote 19 (explaining why
          <tt>\?</tt> is recognized as a simple escape sequence) into a
          note.</li>
      <li>[lex.string]: Modified ordinary and wide string literals that specify
          characters that are not representable in the applicable character
          encoding to be conditionally supported.</li>
      <li>[lex.string]p6,7,9-11: Replaced these paragraphs with a table that
          defines the kinds of string literals and their properties.</li>
    </ul>
  </li>
  <li>Updated the implementation impact section to note Visual C++'s current
      handling of character literals for characters that lack representation
      in the execution character set.</li>
</ul>
</p>


<h1 id="proposed">Proposed resolution overview</h1>

<p>
The proposed wording changes are intended to resolve
<a href="http://wg21.link/cwg411">CWG 411</a>,
<a href="http://wg21.link/cwg1656">CWG 1656</a>, and
<a href="http://wg21.link/cwg2333">CWG 2333</a> by:
<ul>
  <li>Clarifying that hexadecimal and octal escape sequences:
    <ul>
      <li>are valid in <tt>u8</tt>, <tt>u</tt>, and <tt>U</tt> character
          literals.  (CWG 2333)</li>
      <li>specify values that need not correspond to valid code unit
          values for the applicable character encoding.  (CWG 2333)</li>
      <li>specify the execution-time value of character literals or individual
          code unit values of string literals; that the value expressed is not
          subject to conversion to the applicable execution character set.
          (CWG 1656)</li>
      <li>specify values that may result in string literals that are ill-formed
          according to their applicable character encoding (CWG 2333).</li>
    </ul>
  <li>Clarifying that characters that cannot be specified in a character
      literal because they require more than one code unit in the applicable
      character encoding may be specified in string literals.  (CWG 411)</li>
</ul>
</p>

<p>
Additionally, the wording updates are intended to:
<ul>
  <li>Specify behavior for non-ordinary character and string literals when a
      character lacks representation in the applicable character encoding.
      (Wording was previously missing)</li>
  <li>Specify that wide multicharacter literals are conditionally
      supported.</li>
  <li>Specify that ordinary and wide string literals that specify characters
      that are not representable in the applicable character encoding are
      conditionally supported.</li>
  <li>Specify that wide character literals that have a <tt>c-char-sequence</tt>
      that specifies a character that is not representable in the execution
      wide-character set or that cannot be encoded in a single code unit are
      conditionally supported.</li>
  <li>Remove non-normative wording that states that <tt>wchar_t</tt> is able to
      represent all members of the execution wide-character set as this
      contradicts wide spread existing practice (SG16 has an issue tracking
      this at
      <a href="https://github.com/sg16-unicode/sg16/issues/9">https://github.com/sg16-unicode/sg16/issues/9</a>).
  <li>Modernize the wording with current style preferences and terminology.</li>
</ul>
</p>

<p>
The concept of an "associated character encoding" is introduced for character
and string literals so as to enable wording to be independent of the particular
kind of literal (ordinary, wide or Unicode).
</p>

<p>
New <tt>basic-c-char</tt>, <tt>basic-s-char</tt>,
<tt>character-escape-sequence</tt>, <tt>numeric-escape-sequence</tt>, and
<tt>simple-escape-sequence-char</tt> grammar productions are proposed in order
to simplify wording.  The <tt>c-char</tt>, <tt>s-char</tt>, and
<tt>escape-sequence</tt> grammar productions are updated to define them in
terms of the new grammar productions.
</p>

<p>
New <tt>conditional-escape-sequence</tt> and
<tt>conditional-escape-sequence-char</tt> grammar production are proposed to
address previously missing grammar support for conditionally-supported
implementation-defined escape sequences.
</p>

<p>
New <tt>multicharacter literal</tt> and
<tt>wide multicharacter literal</tt>
character literal kinds are defined in order to simplify wording.  These new
kinds cover the cases where an ordinary or wide character literal has a
<tt>c-char-sequence</tt> containing more than one
<tt>c-char</tt>.
</p>

<p>
New <tt>conditional character literal</tt> and
<tt>conditional wide character literal</tt>
character literal kinds are defined in order to simplify wording.  These new
kinds cover the cases where the character specified by the
<tt>c-char-sequence</tt> lacks representation in the
execution (wide-)character set or cannot be encoded in a single code unit.
</p>


<h1 id="impact">Implementation impact</h1>

<p>
The author intends the proposed wording to reflect existing practice for the
gcc and Clang compilers.  If this proposal is adopted, neither of those
compilers are expected to require updates.
However, there is implementation impact to the Microsoft Visual C++ compiler.
</p>

<h2 id="impact-escapes">Semantics of numeric-escape-sequences in UTF-8 literals</h2>

<p>
Consider the following (C++20) code:
<div style="margin-left: 1em;">
<pre><code>constexpr const char8_t c[] = u8"\xc3\x80"; // UTF-8 encoding of U+00C0 {LATIN CAPITAL LETTER A WITH GRAVE}
#if defined(_MSC_VER)
  // Microsoft Visual C++:
  static_assert(c[0] == 0xC3); // UTF-8 encoding of U+00C3 {LATIN CAPITAL LETTER A WITH TILDE}
  static_assert(c[1] == 0x83);
  static_assert(c[2] == 0xC2); // UTF-8 encoding of U+0080 {&lt;control&gt;}
  static_assert(c[3] == 0x80);
  static_assert(c[4] == 0x00); // null
#else
  // Gcc and Clang:
  static_assert(c[0] == 0xC3); // UTF-8 encoding of U+00C0 {LATIN CAPITAL LETTER A WITH GRAVE}
  static_assert(c[1] == 0x80);
  static_assert(c[2] == 0x00); // null
#endif
</code></pre>
</div>
Gcc and Clang encode the hexadecimal escapes as code units in the target (UTF-8)
encoding and perform no conversions (consistent with the behavior intended by
this proposal).  However, Visual C++ considers each hexadecimal escape to
specify a code point in the source encoding and encodes each as UTF-8.
</p>

<p>
The author does not know if the Visual C++ behavior exhibited for UTF-8 literals
is intentional or reflective of a defect.  The behavior is inconsistent for
UTF-8 and UTF-16 literals.  For UTF-8 literals, numeric escape sequences that
specify values outside the range of <tt>char8_t</tt> are accepted as code
point values and encoded as UTF-8.  However, for UTF-16 literals, numeric escape
sequences that specify values outside the range of <tt>char16_t</tt> are
rejected rather than being considered a code point value and encoded as a UTF-16
surrogate pair.
</p>

<h2 id="impact-badchar">Character literal type for characters not representable in the execution character set</h2>

<p>
Consider the following code assuming that the execution character set does not
have representation for the specified Unicode code points.
<div style="margin-left: 1em;">
<pre><code>auto c1 = '\uFF10';
extern char c1;
#ifdef _MSC_VER
static_assert('\uFF10' == '?');
#endif
auto c2 = '\U0001F235';
extern int c2;
#ifdef _MSC_VER
static_assert('\U0001F235' == '??');
#endif
</code></pre>
</div>
This code should be rejected (both before and after this proposal) because the
redeclaration of <tt>c1</tt> with type <tt>char</tt> does not match the first
declaration for which <tt>c1</tt> should have a deduced type of <tt>int</tt>.
Visual C++ accepts it when compiled with <tt>/execution-charset:windows-1252</tt>
with the following warnings:
<div style="margin-left: 1em;">
<pre><code>&lt;source&gt;(1): warning C4566: character represented by universal-character-name '\uFF10' cannot be represented in the current code page (1252)
&lt;source&gt;(4): warning C4566: character represented by universal-character-name '\uFF10' cannot be represented in the current code page (1252)
&lt;source&gt;(6): warning C4566: character represented by universal-character-name '\U0001F235' cannot be represented in the current code page (1252)
&lt;source&gt;(9): warning C4566: character represented by universal-character-name '\U0001F235' cannot be represented in the current code page (1252)
</code></pre>
</div>
It seems that the Visual C++ compiler translates unrepresentable characters
from the Unicode BMP to a single <tt>char</tt> with value equal to
<tt>'?'</tt>, but translates unrepresentable characters from outside the
Unicode BMP to <tt>int</tt> with value equal to the multicharacter literal
<tt>'??'</tt>.  This seems unlikely to be intended behavior.  It would be
conforming if, for the Unicode BMP case, an <tt>int</tt> with value equal
to <tt>'?'</tt> was produced.
</p>

<p>
Gcc and Clang both reject the above code regardless of whether those Unicode
characters have representation in the execution character set.  If they are
representable, then the code is rejected (as permitted) because the characters
cannot be encoded in a single code unit.  If they are not representable (which
only happens for gcc since Clang always targets UTF-8), then the code is
rejected because the redeclaration of <tt>c1</tt> as <tt>char</tt> does not
match the deduced <tt>int</tt> type for its first declaration.
</p>


<h1 id="ack">Acknowledgements</h1>

<p>Thank you to Jens Maurer and Steve Downey for providing feedback on initial
drafts of this paper!
</p>


<h1 id="pr">Proposed resolution</h1>

<p>These changes are relative to
<a title="Working Draft, Standard for Programming Language C++"
   href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/n4835.pdf">
N4835</a>.
</p>

<p>The changes to
<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a> and
<a href="http://eel.is/c++draft/lex.string">[lex.string]</a>
are rather pervasive.  For ease of review, unchanged paragraphs in these
sections are retained in the wording below.  These paragraphs are
introduced with "<em>No</em> changes to ..." and are <nop>highlighted with
a blue background</nop>.
</p>

<p>These changes do not reflect recent editorial changes made in
<a href="https://github.com/cplusplus/draft/pull/2768">
https://github.com/cplusplus/draft/pull/2768</a>;
merge conflict resolution will be required.
</p>

<input type="checkbox" id="hideins">Hide inserted text</input><br/>
<input type="checkbox" id="hidedel">Hide deleted text</input>

<h2 id="lex.phases">[lex.phases]</h2>

<p>Change in
<a href="http://eel.is/c++draft/lex.phases#1.5">
5.2 [lex.phases] paragraph 5</a>:<br/>
<em>Drafting Note:</em> The change of "escape sequence" to
"<tt>character-escape-sequence</tt>" addresses
<a href="http://wg21.link/cwg1656">CWG 1656</a>.
<blockquote>
Each <del>basic source character set member</del><ins><a href="http://eel.is/c++draft/lex.ccon#nt:basic-c-char"><em>basic-c-char</em></a>,
<a href="http://eel.is/c++draft/lex.string#nt:basic-s-char"><em>basic-s-char</em></a>, and
<a href="http://eel.is/c++draft/lex.string#nt:r-char"><em>r-char</em></a>
</ins>
in a character literal or a string literal, as well as each
<del>escape sequence</del><ins><a href="http://eel.is/c++draft/lex.ccon#nt:character-escape-sequence"><em>character-escape-sequence</em></a></ins>
and
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
in a character literal or a non-raw string literal, is converted to the
<del>corresponding member of the execution character set
(<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>,
<a href="http://eel.is/c++draft/lex.string">[lex.string]</a>);
</del><ins>literal's
associated character encoding as specified in
<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a> and
<a href="http://eel.is/c++draft/lex.string">[lex.string]</a>.</ins>
<del>if there is no corresponding member, it is converted to an implementation
defined member other than the null (wide) character</del>
<ins>[ <em>Note:</em> If a character lacks representation in the associated
character encoding, then the character is converted to an
implementation-defined character or the literal is ill-formed
(<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>,
<a href="http://eel.is/c++draft/lex.string">[lex.string]</a>)
&mdash; <em>end note</em> ]</ins>.
<sup><a href="http://eel.is/c++draft/lex.phases#footnote-8">8</a></sup>
</blockquote>
</p>

<p>Change in
<a href="http://eel.is/c++draft/lex.phases#1.7">
5.2 [lex.phases] paragraph 7</a>:<br/>
<em>Drafting note:</em> This addition duplicates wording in [lex.string], but
seems important to include here.
<blockquote>
<ins>A null character is appended to every
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>.
</ins>White-space
characters separating tokens are no longer significant. Each
preprocessing token is converted into a token
(<a href="http://eel.is/c++draft/lex.token">[lex.token]</a>).  The resulting
tokens are syntactically and semantically analyzed and translated as a
translation unit.  [ <em>Note:</em> The process of analyzing and translating
the tokens may occasionally result in one token being replaced by a sequence
of other tokens
(<a href="http://eel.is/c++draft/temp.names">[temp.names]</a>).
&mdash; <em>end note</em> ]  It is implementation-defined whether the sources
for module units and header units on which the current translation unit has an
interface dependency
(<a href="http://eel.is/c++draft/module.unit">[module.unit]</a>,
<a href="http://eel.is/c++draft/module.import">[module.import]</a>)
are required to be available. [ <em>Note:</em> Source files, translation units
and translated translation units need not necessarily be stored as files, nor
need there be any one-to-one correspondence between these entities and any
external representation.  The description is conceptual only, and does not
specify any particular implementation. &mdash; <em>end note</em> ]
</blockquote>
</p>

<h2 id="lex.ccon">[lex.ccon]</h2>

<p>Change in
<a href="http://eel.is/c++draft/lex.ccon">
5.13.3 [lex.ccon]</a>:
<blockquote>
<a href="http://eel.is/c++draft/lex.ccon#nt:character-literal">character-literal:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix">encoding-prefix</a><sub>opt</sub>
<tt>'</tt>
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence">c-char-sequence</a>
<tt>'</tt>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix">encoding-prefix:</a> one of
<div style="margin-left: 1em;">
<tt>u8</tt>&ensp; <tt>u</tt>&ensp; <tt>U</tt>&ensp; <tt>L</tt>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence">c-char-sequence:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char">c-char</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence">c-char-sequence</a>
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char">c-char</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char">c-char:</a>
<del><div style="margin-left: 1em;">
any member of the basic source character set except the single-quote <tt>'</tt>,
backslash <tt>\</tt>, or
<a href="http://eel.is/c++draft/cpp.pre#nt:new-line">new-line</a>
character
</div></del>
<ins><div style="margin-left: 1em;">
basic-c-char
</div></ins>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:escape-sequence">escape-sequence</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name">universal-character-name</a>
</div>
<br/>
<ins>basic-c-char:
<div style="margin-left: 1em;">
any member of the basic source character set except the single-quote <tt>'</tt>,
backslash <tt>\</tt>, or
<a href="http://eel.is/c++draft/cpp.pre#nt:new-line">new-line</a>
character
</div>
<br/></ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:escape-sequence">escape-sequence:</a>
<del><div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence">simple-escape-sequence</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:octal-escape-sequence">octal-escape-sequence</a>
</div></del>
<del><div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence">hexadecimal-escape-sequence</a>
</div></del>
<div style="margin-left: 1em;">
<ins><a href="http://eel.is/c++draft/lex.ccon#nt:character-escape-sequence">character-escape-sequence</a></ins>
</div>
<div style="margin-left: 1em;">
<ins><a href="http://eel.is/c++draft/lex.ccon#nt:numeric-escape-sequence">numeric-escape-sequence</a></ins>
</div>
<br/>
<ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:character-escape-sequence">character-escape-sequence</a>:
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence">simple-escape-sequence</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:conditional-escape-sequence">conditional-escape-sequence</a>
</div>
<br/>
</ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence">simple-escape-sequence:</a><del> one of</del>
<div style="margin-left: 1em;">
<del>
<tt>\'</tt>&ensp; <tt>\"</tt>&ensp; <tt>\?</tt>&ensp; <tt>\\</tt><br/>
<tt>\a</tt>&ensp; <tt>\b</tt>&ensp; <tt>\f</tt>&ensp; <tt>\n</tt>&ensp; <tt>\r</tt>&ensp; <tt>\t</tt>&ensp; <tt>\v</tt>&ensp;<br/>
</del>
<ins>
<tt>\</tt> <a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence-char">simple-escape-sequence-char</a>
</ins>
</div>
<ins><br/></ins>
<ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence-char">simple-escape-sequence-char</a>: one of
<div style="margin-left: 1em;">
<tt>'</tt>&nbsp; <tt>"</tt>&nbsp; <tt>?</tt>&nbsp; <tt>\</tt><br/>
<tt>a</tt>&nbsp; <tt>b</tt>&nbsp; <tt>f</tt>&nbsp; <tt>n</tt>&nbsp; <tt>r</tt>&nbsp; <tt>t</tt>&nbsp; <tt>v</tt>
</div>
<br/>
</ins>
<ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:conditional-escape-sequence">conditional-escape-sequence</a>:
<div style="margin-left: 1em;">
<tt>\</tt> <a href="http://eel.is/c++draft/lex.ccon#nt:conditional-escape-sequence-char">conditional-escape-sequence-char</a>
</div>
<br/>
</ins>
<ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:conditional-escape-sequence-char">conditional-escape-sequence-char</a>:
<div style="margin-left: 1em;">
any member of the basic source character set that is not in
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence-char">simple-escape-sequence-char</a>
</div>
</ins>
<br/>
<ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:numeric-escape-sequence">numeric-escape-sequence</a>:
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:octal-escape-sequence">octal-escape-sequence</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence">hexadecimal-escape-sequence</a>
</div>
<br/>
</ins>
<a href="http://eel.is/c++draft/lex.ccon#nt:octal-escape-sequence">octal-escape-sequence:</a>
<div style="margin-left: 1em;">
<tt>\</tt> <a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
</div>
<div style="margin-left: 1em;">
<tt>\</tt> <a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
<a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
</div>
<div style="margin-left: 1em;">
<tt>\</tt> <a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
<a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
<a href="http://eel.is/c++draft/lex.icon#nt:octal-digit">octal-digit</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence">hexadecimal-escape-sequence:</a>
<div style="margin-left: 1em;">
<tt>\x</tt> <a href="http://eel.is/c++draft/lex.icon#nt:hexadecimal-digit">hexadecimal-digit</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence">hexadecimal-escape-sequence</a>
<a href="http://eel.is/c++draft/lex.icon#nt:hexadecimal-digit">hexadecimal-digit</a>
</div>
</blockquote>
</p>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.ccon#1">
5.13.3 [lex.ccon] paragraph 1</a>:<br/>
<em>Drafting Note:</em> Per discussion in the
<a href="http://wiki.edg.com/bin/view/Wg21prague/IssuesProcessingTeleconference2020-01-16">January 16th, 2020 core issues processing teleconference</a>,
this paragraph will be editorially deleted and all occurrences of
"character literal" will be replaced with references to the
<tt><em>character-literal</em></tt> grammar production.
<blockquote class="stdnop">
A character literal is one or more characters enclosed in single quotes, as in
<tt>'x'</tt>, optionally preceded by
<tt>u8</tt>, <tt>u</tt>, <tt>U</tt>, or <tt>L</tt></del>,
as in <tt>u8'w'</tt>, <tt>u'x'</tt>, <tt>U'y'</tt>, or <tt>L'z'</tt>, respectively.
</blockquote>
</p>

<p>Add a new paragraph and table (X) after
<a href="http://eel.is/c++draft/lex.ccon#1">
5.13.3 [lex.ccon] paragraph 1</a>:
<blockquote class="stdins">
Table X specifies the kinds of
<a href="http://eel.is/c++draft/lex.ccon#nt:character-literal"><em>character-literal</em></a>s
and their properties.

The type of a
<a href="http://eel.is/c++draft/lex.ccon#nt:character-literal"><em>character-literal</em></a>
is the associated code unit type.

<em>conditional character literal</em>s and
<em>conditional wide character literal</em>s
are distinguished from
<em>ordinary character literal</em>s and
<em>wide character literal</em>s
respectively by the presence of a
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence"><em>c-char-sequence</em></a>
that contains a single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
that is not a
<a href="http://eel.is/c++draft/lex.ccon#nt:numeric-escape-sequence"><em>numeric-escape-sequence</em></a>
and that specifies a character that either lacks representation in the
applicable associated character encoding or that cannot be encoded
in a single code unit.

<em>multicharacter literal</em>s and
<em>wide multicharacter literal</em>s
are distinguished from
<em>ordinary character literal</em>s and
<em>wide character literal</em>s
respectively by the presence of a
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence"><em>c-char-sequence</em></a>
that contains more than one
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>;
the
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char-sequence"><em>c-char-sequence</em></a>
of all other character literals contains exactly one
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>.

<em>conditional character literal</em>s,
<em>multicharacter literal</em>s,
<em>conditional wide character literal</em>s, and
<em>wide multicharacter literal</em>s
are conditionally supported.
</blockquote>
</p>

<blockquote class="stdins">
<div align="center">
<table border="0">
<tr>
<td align="left">Table X: Character literals
<td/>
<td align="right">[tab:lex.ccon.literals]</td>
</tr>
</table>
<br/>
<table border="1">
<tr>
  <th>Kind</th>
  <th>Encoding<br/>prefix</th>
  <th>Associated<br/>code unit type</th>
  <th>Associated<br/>character encoding</th>
  <th>Example</th>
</tr>
<tr>
  <td><em>ordinary character literal</em></td>
  <td>none</td>
  <td><tt>char</tt></td>
  <td>encoding of the execution character set</td>
  <td><tt>'v'</tt></td>
</tr>
<tr>
  <td><em>conditional character literal</em></td>
  <td>none</td>
  <td><tt>int</tt></td>
  <td>implementation-defined</td>
  <td>
    <tt>'\U0001F525'</tt><br/>
    (assuming lack of representation in the execution character set,<br/>
    or that representation would require more than one code unit.)
  </td>
</tr>
<tr>
  <td><em>multicharacter literal</em></td>
  <td>none</td>
  <td><tt>int</tt></td>
  <td>implementation-defined</td>
  <td><tt>'abcd'</tt></td>
</tr>
<tr>
  <td><em>wide character literal</em></td>
  <td><tt>L</tt></td>
  <td><tt>wchar_t</tt></td>
  <td>encoding of the execution wide-character set</td>
  <td><tt>L'w'</tt></td>
</tr>
<tr>
  <td><em>conditional wide character literal</em></td>
  <td><tt>L</tt></td>
  <td><tt>wchar_t</tt></td>
  <td>implementation-defined</td>
  <td>
    <tt>L'\U0001F32A'</tt><br/>
    (assuming lack of representation in the execution wide-character set,<br/>
    or that representation would require more than one code unit.)
  </td>
</tr>
<tr>
  <td><em>wide multicharacter literal</em></td>
  <td><tt>L</tt></td>
  <td><tt>wchar_t</tt></td>
  <td>implementation-defined</td>
  <td><tt>L'abcd'</tt></td>
</tr>
<tr>
  <td><em>UTF-8 character literal</em></td>
  <td><tt>u8</tt></td>
  <td><tt>char8_t</tt></td>
  <td>UTF-8</td>
  <td><tt>u8'x'</tt></td>
</tr>
<tr>
  <td><em>UTF-16 character literal</em></td>
  <td><tt>u</tt></td>
  <td><tt>char16_t</tt></td>
  <td>UTF-16</td>
  <td><tt>u'y'</tt></td>
</tr>
<tr>
  <td><em>UTF-32 character literal</em></td>
  <td><tt>U</tt></td>
  <td><tt>char32_t</tt></td>
  <td>UTF-32</td>
  <td><tt>U'z'</tt></td>
</tr>
</table>
</div>
</blockquote>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#2">
5.13.3 [lex.ccon] paragraph 2</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 2-6 were incorporated into
new paragraphs.
<blockquote class="stddel">
A character literal that does not begin with
<tt>u8</tt>, <tt>u</tt>,
<tt>U</tt>, or <tt>L</tt>
is an <em>ordinary character literal</em>.
An ordinary character literal that contains a single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
representable in the execution character set
has type <tt>char</tt>, with value equal to the numerical value of the encoding
of the
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
in the execution character set.  An ordinary character literal that
contains more than one
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
is a <em>multicharacter literal</em>.  A multicharacter literal, or an
ordinary character literal containing a single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
not representable in the execution character set, is conditionally-supported,
has type <tt>int</tt>, and has an implementation-defined value.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#3">
5.13.3 [lex.ccon] paragraph 3</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 2-6 were incorporated into
new paragraphs.  The note regarding the range of single code unit values was
removed.
<blockquote class="stddel">
A character literal that begins with <tt>u8</tt>, such as <tt>u8'w'</tt>, is a
character literal of type <tt>char8_t</tt>, known as a
<em>UTF-8 character literal</em>.
The value of a UTF-8 character literal is
equal to its ISO/IEC 10646 code point value, provided that the code point value
can be encoded as a single UTF-8 code unit.  [ <em>Note:</em> That is, provided
the code point value is in the range 0x0-0x7F (inclusive). &mdash;
<em>end note</em> ]   If the value is not representable with a single UTF-8 code
unit, the program is ill-formed.  A UTF-8 character literal containing multiple
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>s is
ill-formed.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#4">
5.13.3 [lex.ccon] paragraph 4</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 2-6 were incorporated into
new paragraphs.  The note regarding the range of singled code unit values was
removed.
<blockquote class="stddel">
A character literal that begins with the letter <tt>u</tt>, such as
<tt>u'x'</tt>, is a character literal of type <tt>char16_t</tt>, known as a
<em>UTF-16 character literal</em>.  The value of a UTF-16 character literal
is equal to its ISO/IEC 10646 code point value, provided that the code point
value is representable with a single 16-bit code unit. [ <em>Note:</em> That
is, provided the code point value is in the range 0x0-0xFFFF (inclusive).
&mdash; <em>end note</em> ]  If the value is not representable with a single
16-bit code unit, the program is ill-formed.  A UTF-16 character literal
containing multiple
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>s is
ill-formed.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#5">
5.13.3 [lex.ccon] paragraph 5</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 2-6 were incorporated into
new paragraphs.
<blockquote class="stddel">
A character literal that begins with <tt>U</tt>, such as <tt>U'y'</tt>, is a
character literal of type <tt>char32_t</tt>, known as a
<em>UTF-32 character literal</em>.
The value of a UTF-32 character literal containing a single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
is equal to its ISO/IEC 10646 code point value.  A UTF-32 character literal
containing multiple
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>s is
ill-formed.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#6">
5.13.3 [lex.ccon] paragraph 6</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 2-6 were incorporated into
new paragraphs.
The note regarding the ability for <tt>wchar_t</tt> to store all
values of the execution wide-character set is intentionally removed as it
conflicts with long standing existing practice
(<a href="https://github.com/sg16-unicode/sg16/issues/9">https://github.com/sg16-unicode/sg16/issues/9</a>).
The reference to footnote 18 and the footnote itself are also removed.
<blockquote class="stddel">
A character literal that begins with the letter <tt>L</tt>, such as
<tt>L'z'</tt>, is a <em>wide-character literal</em>.  A wide-character literal
has type <tt>wchar_t</tt>.<sup><a href="http://eel.is/c++draft/lex.ccon#footnote-18">18</a></sup>
The value of a wide-character literal containing a single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
has value equal to the numerical value of the encoding of the
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
in the execution wide-character set, unless the
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
has no representation in the execution wide-character set, in which case the
value is implementation-defined.
[ <em>Note:</em> The type <tt>wchar_t</tt> is able to represent all members of
the execution wide-character set (see
<a href="http://eel.is/c++draft/basic.fundamental">[basic.fundamental]</a>).
&mdash; <em>end note</em> ]
The value of a wide-character literal containing multiple
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>s
is implementation-defined.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#footnote-18">footnote 18</a><br/>
<em>Drafting Note:</em> The reference to this footnote was removed and the note
itself found to have too little value to retain elsewhere.
<blockquote class="stddel">
18) They are intended for character sets where a character does not fit into a
single byte.
</blockquote>
</p>

<p>Add a new paragraph (X):
<blockquote class="stdins">
The value of a character literal is as follows.
<table>
  <tr>
    <td>(X.1)&nbsp;&mdash;</td>
    <td>
      The value of a
      <em>conditional character literal</em>,
      <em>multicharacter literal</em>,
      <em>conditional wide character literal</em>, or
      <em>wide multicharacter literal</em>
      is implementation-defined.
    </td>
  </tr>
  <tr>
    <td>(X.2)&nbsp;&mdash;</td>
    <td>
      The value of a character literal consisting of a single
      <a href="http://eel.is/c++draft/lex.ccon#nt:basic-c-char"><em>basic-c-char</em></a>,
      <a href="http://eel.is/c++draft/lex.ccon#nt:character-escape-sequence"><em>character-escape-sequence</em></a>, or
      <a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
      is the code unit value of the specified character encoded with the
      character literal's associated character encoding.
      If the character cannot be encoded in a single code unit, then
      the character literal is either a
      <em>conditional character literal</em>, a
      <em>conditional wide character literal</em>,
      or is ill-formed.
    </td>
  </tr>
  <tr>
    <td>(X.3)&nbsp;&mdash;</td>
    <td>
      The value of a character literal consisting of a single
      <a href="http://eel.is/c++draft/lex.ccon#nt:numeric-escape-sequence"><em>numeric-escape-sequence</em></a>
      is the numeric value of the octal or hexadecimal number.  There is no limit
      to the number of digits in a hexadecimal sequence.  A sequence of octal or
      hexadecimal digits is terminated by the first character that is not an octal
      digit or a hexadecimal digit, respectively.  If the numeric value exceeds the
      range of the character literal's associated code unit type, then, for an
      <em>ordinary character literal</em> or a
      <em>wide character literal</em>, the value is implementation-defined and, for
      all other character literals, the character literal is ill-formed.
    </td>
  </tr>
</table>
</blockquote>
</p>

<p>Change in
<a href="http://eel.is/c++draft/lex.ccon#7">
5.13.3 [lex.ccon] paragraph 7</a>:<br/>
<em>Drafting Note:</em> The added note is content moved from
<a href="http://eel.is/c++draft/lex.ccon#footnote-19">footnote 19</a>.
The deleted text has been removed as redundant since it repeats information
implicit in the grammar.
<blockquote>
<ins>The character specified by a
<a href="http://eel.is/c++draft/lex.ccon#nt:simple-escape-sequence"><em>simple-escape-sequence</em></a>
is specified in table
<a href="http://eel.is/c++draft/lex.ccon#tab:lex.ccon.esc">8</a>.
[ <em>Note:</em> Using an escape sequence for a question mark is supported for
compatibility with ISO C++ 2014 and ISO C.  &mdash; <em>end note</em> ]
<a href="http://eel.is/c++draft/lex.ccon#nt:conditional-escape-sequence"><em>conditional-escape-sequence</em></a>s
are conditionally-supported and specify an implementation-defined
character.</ins>
<del>Certain non-graphic characters, the single quote <tt>'</tt>, the double quote
<tt>"</tt>, the question mark
<tt>?</tt>,<sup><a href="http://eel.is/c++draft/lex.ccon#footnote-19">19</a></sup>
and the backslash <tt>\</tt>, can be represented according to Table
<a href="http://eel.is/c++draft/lex.ccon#tab:lex.ccon.esc">8</a>.
The double quote <tt>"</tt> and the question mark <tt>?</tt>, can be
represented as themselves or by the escape sequences <tt>\"</tt> and <tt>\?</tt>
respectively, but the single quote <tt>'</tt> and the backslash <tt>\</tt> shall
be represented by the escape sequences <tt>\'</tt> and <tt>\\</tt> respectively.
Escape sequences in which the character following the backslash is not listed in
Table <a href="http://eel.is/c++draft/lex.ccon#tab:lex.ccon.esc">8</a>
are conditionally-supported, with implementation-defined semantics.  An escape
sequence specifies a single character.
</del>
<br/>
<br/>
<div align="center">
<table border="0">
<tr>
<td align="left">Table <a href="http://eel.is/c++draft/lex.ccon#tab:lex.ccon.esc">8</a>:
<del>E</del><ins>Simple e</ins>scape sequences</td>
<td/>
<td align="right">[tab:lex.ccon.esc]</td>
</tr>
</table>
<br/>
<table border="1">
<tr><td>new-line</td>       <td>NL(LF)</td><td><tt>\n</tt></td></tr>
<tr><td>horizontal tab</td> <td>HT</td>    <td><tt>\t</tt></td></tr>
<tr><td>vertical tab</td>   <td>VT</td>    <td><tt>\v</tt></td></tr>
<tr><td>backspace</td>      <td>BS</td>    <td><tt>\b</tt></td></tr>
<tr><td>carriage return</td><td>CR</td>    <td><tt>\r</tt></td></tr>
<tr><td>form feed</td>      <td>FF</td>    <td><tt>\f</tt></td></tr>
<tr><td>alert</td>          <td>BEL</td>   <td><tt>\a</tt></td></tr>
<tr><td>backslash</td>      <td>\</td>     <td><tt>\\</tt></td></tr>
<tr><td>question mark</td>  <td>?</td>     <td><tt>\?</tt></td></tr>
<tr><td>single quote</td>   <td>'</td>     <td><tt>\'</tt></td></tr>
<tr><td>double quote</td>   <td>"</td>     <td><tt>\"</tt></td></tr>
<tr><td><del>octal number</del></td>   <td><del>ooo</del></td>   <td><tt><del>\ooo</del></tt></td></tr>
<tr><td><del>hex number</del></td>     <td><del>hhh</del></td>   <td><tt><del>\xhhh</del></tt></td></tr>
</table>
</div>
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#footnote-19">footnote 19</a>
referenced from
<a href="http://eel.is/c++draft/lex.ccon#7">
5.13.3 [lex.ccon] paragraph 7</a>:<br/>
<em>Drafting Note:</em> The footnote text was moved into a note in
<a href="http://eel.is/c++draft/lex.ccon#7">[lex.ccon] paragraph 7</a>.
<blockquote class="stddel">
19) Using an escape sequence for a question mark is supported for compatibility with ISO C++ 2014 and ISO C.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#8">
5.13.3 [lex.ccon] paragraph 8</a>:<br/>
<em>Drafting Note:</em> Wording describing the form of octal and hexadecimal
escape sequences has been removed as redundant; the form is implicit in the
grammar.
<blockquote class="stddel">
The escape <tt>\ooo</tt> consists of the backslash followed by one, two, or
three octal digits that are taken to specify the value of the desired character.
The escape <tt>\xhhh</tt> consists of the backslash followed by <tt>x</tt>
followed by one or more hexadecimal digits that are taken to specify the value
of the desired character.  </del>There is no limit to the number of digits in a
hexadecimal sequence.  A sequence of octal or hexadecimal digits is terminated
by the first character that is not an octal digit or a hexadecimal digit,
respectively.
The value of a character literal is implementation-defined if it
falls outside of the implementation-defined range defined for <tt>char</tt>
(for character literals with no prefix) or <tt>wchar_t</tt> (for character
literals prefixed by <tt>L</tt>).  [ <em>Note:</em> If the value of
a character literal prefixed by <tt>u</tt>, <tt>u8</tt>, or <tt>U</tt> is
outside the range defined for its type, the program is ill-formed.
&mdash; <em>end note</em> ]
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.ccon#9">
5.13.3 [lex.ccon] paragraph 9</a>:<br/>
<em>Drafting Note:</em> The normative text was combined with wording for
<tt>basic-c-char</tt> and <tt>character-escape-sequence</tt> above.  The deleted
note duplicates normative text in
<a href="http://eel.is/c++draft/lex.phases#1.1">
5.2 [lex.phases] paragraph 1</a>.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
is translated to the encoding, in the appropriate execution character set, of
the character named.  If there is no such encoding, the
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
is translated to an implementation-defined encoding.
[ <em>Note:</em> In translation phase 1, a
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
is introduced whenever an actual extended character is encountered in the
source text.  Therefore, all extended characters are described in terms of
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>s
However, the actual compiler implementation may use its own native character
set, so long as the same results are obtained.  &mdash; <em>end note</em> ]
</blockquote>
</p>

<h2 id="lex.string">[lex.string]</h2>

<p>Change in
<a href="http://eel.is/c++draft/lex.string">
5.13.5 [lex.string]</a>:
<blockquote>
<a href="http://eel.is/c++draft/lex.string#nt:string-literal">string-literal:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix">encoding-prefix</a><sub>opt</sub>
<tt>"</tt>
<a href="http://eel.is/c++draft/lex.string#nt:s-char-sequence">s-char-sequence</a><sub>opt</sub>
<tt>"</tt>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix">encoding-prefix</a><sub>opt</sub>
<tt>R</tt>
<a href="http://eel.is/c++draft/lex.string#nt:raw-string">raw-string</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:s-char-sequence">s-char-sequence:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:s-char">s-char</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:s-char-sequence">s-char-sequence</a>
<a href="http://eel.is/c++draft/lex.string#nt:s-char">s-char</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:s-char">s-char:</a>
<del><div style="margin-left: 1em;">
any member of the basic source character set except the double-quote <tt>"</tt>,
backslash <tt>\</tt>, or
<a href="http://eel.is/c++draft/cpp.pre#nt:new-line">new-line</a>
character
</div></del>
<ins><div style="margin-left: 1em;">
basic-s-char
</div></ins>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:escape-sequence">escape-sequence</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name">universal-character-name</a>
</div>
<br/>
<ins>basic-s-char:
<div style="margin-left: 1em;">
any member of the basic source character set except the double-quote <tt>"</tt>,
backslash <tt>\</tt>, or
<a href="http://eel.is/c++draft/cpp.pre#nt:new-line">new-line</a>
character
</div>
<br/></ins>
<a href="http://eel.is/c++draft/lex.string#nt:raw-string">raw-string:</a>
<div style="margin-left: 1em;">
<tt>"</tt>
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence">d-char-sequence</a><sub>opt</sub>
<tt>(</tt>
<a href="http://eel.is/c++draft/lex.string#nt:r-char-sequence">r-char-sequence</a><sub>opt</sub>
<tt>)</tt>
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence">d-char-sequence</a><sub>opt</sub>
<tt>"</tt>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:r-char-sequence">r-char-sequence:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:r-char">r-char</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:r-char-sequence">r-char-sequence</a>
<a href="http://eel.is/c++draft/lex.string#nt:r-char">r-char</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:r-char">r-char:</a>
<div style="margin-left: 1em;">
any member of the source character set, except a right parenthesis <tt>)</tt> followed by
<div style="margin-left: 1em;">
the initial
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence">d-char-sequence</a>
(which may be empty) followed by a double quote <tt>"</tt>.
</div>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence">d-char-sequence:</a>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:d-char">d-char</a>
</div>
<div style="margin-left: 1em;">
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence">d-char-sequence</a>
<a href="http://eel.is/c++draft/lex.string#nt:d-char">d-char</a>
</div>
<br/>
<a href="http://eel.is/c++draft/lex.string#nt:d-char">d-char:</a>
<div style="margin-left: 1em;">
any member of the source character set except:
<div style="margin-left: 1em;">
space, the left parenthesis <tt>(</tt>, the right parenthesis <tt>)</tt>, the
backslash <tt>\</tt>, and the control characters<br/>
representing horizontal tab, vertical tab, form feed, and newline.
</div>
</div>
</blockquote>
</p>


<p>Delete
<a href="http://eel.is/c++draft/lex.string#1">
5.13.5 [lex.string] paragraph 1</a>:<br/>
<em>Drafting Note:</em> The contents of paragraph 1 was incorporated into new
paragraphs.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
is a sequence of characters (as defined in
<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>)
surrounded by double quotes, optionally prefixed by
<tt>R</tt>,
<tt>u8</tt>, <tt>u8R</tt>,
<tt>u</tt>, <tt>uR</tt>,
<tt>U</tt>, <tt>UR</tt>,
<tt>L</tt>, or <tt>LR</tt>, as in
<tt>"..."</tt>,
<tt>R"(...)"</tt>, <tt>u8"..."</tt>,
<tt>u8R"**(...)**"</tt>, <tt>u"..."</tt>,
<tt>uR"*~(...)*~"</tt>, <tt>U"..."</tt>,
<tt>UR"zzz(...)zzz"</tt>, <tt>L"..."</tt>, or <tt>LR"(...)"</tt>, respectively.
</blockquote>
</p>

<p>Add a new paragraph and table (X) after
<a href="http://eel.is/c++draft/lex.string#1">
5.13.5 [lex.string] paragraph 1</a>:
<blockquote class="stdins">
Table X specifies the kinds of
<a href="http://eel.is/c++draft/lex.ccon#nt:string-literal"><em>string-literal</em></a>s
and their properties.
</blockquote>
</p>

<blockquote class="stdins">
<div align="center">
<table border="0">
<tr>
<td align="left">Table X: String literals
<td/>
<td align="right">[tab:lex.string.literals]</td>
</tr>
</table>
<br/>
<table border="1">
<tr>
  <th>Kind</th>
  <th>Encoding<br/>prefix</th>
  <th>Type</th>
  <th>Associated<br/>character encoding</th>
  <th>Examples</th>
</tr>
<tr>
  <td><em>ordinary string literal</em></td>
  <td>none</td>
  <td>array of <em>n</em> <tt>const char</tt></td>
  <td>encoding of the execution character set</td>
  <td>
    <tt>""</tt><br/>
    <tt>"an ordinary string"</tt><br/>
    <tt>R"(an ordinary raw string)"</tt>
  </td>
</tr>
<tr>
  <td><em>wide string literal</em></td>
  <td><tt>L</tt></td>
  <td>array of <em>n</em> <tt>const wchar_t</tt></td>
  <td>encoding of the execution wide-character set</td>
  <td>
    <tt>L""</tt><br/>
    <tt>L"a wide string"</tt><br/>
    <tt>LR"w(a wide raw string)w"</tt>
  </td>
</tr>
<tr>
  <td><em>UTF-8 string literal</em></td>
  <td><tt>u8</tt></td>
  <td>array of <em>n</em> <tt>const char8_t</tt></td>
  <td>UTF-8</td>
  <td>
    <tt>u8""</tt><br/>
    <tt>u8"a UTF-8 string"</tt><br/>
    <tt>u8R"x(a UTF-8 raw string)x"</tt>
  </td>
</tr>
<tr>
  <td><em>UTF-16 string literal</em></td>
  <td><tt>u</tt></td>
  <td>array of <em>n</em> <tt>const char16_t</tt></td>
  <td>UTF-16</td>
  <td>
    <tt>u""</tt><br/>
    <tt>u"a UTF-16 string"</tt><br/>
    <tt>uR"y(a UTF-16 raw string)y"</tt>
  </td>
</tr>
<tr>
  <td><em>UTF-32 string literal</em></td>
  <td><tt>U</tt></td>
  <td>array of <em>n</em> <tt>const char32_t</tt></td>
  <td>UTF-32</td>
  <td>
    <tt>U""</tt><br/>
    <tt>U"A UTF-32 string"</tt><br/>
    <tt>UR"z(a UTF-32 raw string)z"</tt>
  </td>
</tr>
</table>
</div>
</blockquote>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.string#2">
5.13.5 [lex.string] paragraph 2</a>:
<blockquote class="stdnop">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that has an <tt>R</tt> in the prefix is a
<a href="http://eel.is/c++draft/lex.string#def:raw_string_literal"><em>raw string literal</em></a>.
The
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence"><em>d-char-sequence</em></a>
serves as a delimiter.
The terminating
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence"><em>d-char-sequence</em></a>
of a
<a href="http://eel.is/c++draft/lex.string#nt:raw-string"><em>raw-string</em></a>
is the same sequence of characters as the initial
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence"><em>d-char-sequence</em></a>.
A
<a href="http://eel.is/c++draft/lex.string#nt:d-char-sequence"><em>d-char-sequence</em></a>
shall consist of at most 16 characters.
</blockquote>
</p>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.string#3">
5.13.5 [lex.string] paragraph 3</a>:
<blockquote class="stdnop">
[ <em>Note:</em> The characters <tt>'('</tt> and <tt>')'</tt> are permitted in a
<a href="http://eel.is/c++draft/lex.string#nt:raw-string"><em>raw-string</em></a>.
Thus, <tt>R"delimiter((a|b))delimiter"</tt> is equivalent to <tt>"(a|b)"</tt>.
&mdash; <em>end note</em> ]
</blockquote>
</p>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.string#4">
5.13.5 [lex.string] paragraph 4</a>:
<blockquote class="stdnop">
[ <em>Note:</em> A source-file new-line in a raw string literal results in a new-line in the resulting execution string literal.
Assuming no whitespace at the beginning of lines in the following example, the assert will succeed:
<div style="margin-left: 1em;">
<pre><code>const char* p = R"(a\
b
c)";
assert(std::strcmp(p, "a\\\nb\nc") == 0);</code></pre>
</div>
&mdash; <em>end note</em> ]
</blockquote>
</p>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.string#5">
5.13.5 [lex.string] paragraph 5</a>:
<blockquote class="stdnop">
[ <em>Example:</em> The raw string
<div style="margin-left: 1em;">
<pre><code>R"a(
)\
a"
)a"</code></pre>
</div>
is equivalent to <tt>"\n)\\\na\"\n"</tt>.  The raw string
<div style="margin-left: 1em;">
<pre><code>R"(x = "\"y\"")"</code></pre>
</div>
is equivalent to <tt>"x = \"\\\"y\\\"\""</tt>.
&mdash; <em>end example</em> ]
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#6">
5.13.5 [lex.string] paragraph 6</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 6, 7, 9, 10, and 11 were
incorporated into new paragraphs.
The wording regarding translation phase 6 has been removed as inaccurate;
string contents are not fully known until after phase 7.
<blockquote class="stddel">
After translation phase 6, a
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that does not begin with an
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix"><em>encoding-prefix</em></a>
is an <em>ordinary string literal</em>.  An ordinary string literal
has type "array of <em>n</em> const char" where <em>n</em> is the size of the
string as defined below, has static storage duration
(<a href="http://eel.is/c++draft/basic.stc">[basic.stc]</a>),
and is initialized with the given characters.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#7">
5.13.5 [lex.string] paragraph 7</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 6, 7, 9, 10, and 11 were
incorporated into new paragraphs.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that begins with <tt>u8</tt>, such as <tt>u8"asdf"</tt>, is a
<em>UTF-8 string literal</em>.  A UTF-8 string literal has type "array of
<em>n</em> const char8_t", where <em>n</em> is the size of the string as
defined below; each successive element of the object representation
(<a href="http://eel.is/c++draft/basic.types">[basic.types]</a>) has the value
of the corresponding code unit of the UTF-8 encoding of the string.
</blockquote>
</p>

<p><em>No</em> changes to
<a href="http://eel.is/c++draft/lex.string#8">
5.13.5 [lex.string] paragraph 8</a>:
<blockquote class="stdnop">
Ordinary string literals and UTF-8 string literals are also referred to as narrow string literals.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#9">
5.13.5 [lex.string] paragraph 9</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 6, 7, 9, 10, and 11 were
incorporated into new paragraphs.
The note has been deleted as redundant; the use of surrogate pairs is explicit
in the UTF-16 encoding.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that begins with <tt>u</tt>, such as <tt>u"asdf"</tt>, is a
<em>UTF-16 string literal</em>.  A UTF-16 string literal has type "array of
<em>n</em> const char16_t", where <em>n</em> is the size of the string as
defined below; each successive element of the array has the value of the
corresponding code unit of the UTF-16 encoding of the string.
[ <em>Note:</em> A single
<a href="http://eel.is/c++draft/lex.ccon#nt:c-char"><em>c-char</em></a>
may produce more than one char16_t character in the form of surrogate pairs.
A surrogate pair is a representation for a single code point as a sequence of
two 16-bit code units.  &mdash; <em>end note</em> ]
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#10">
5.13.5 [lex.string] paragraph 10</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 6, 7, 9, 10, and 11 were
incorporated into new paragraphs.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that begins with <tt>U</tt>, such as <tt>U"asdf"</tt>, is a
<em>UTF-32 string literal</em>.  A UTF-32 string literal has type "array of
<em>n</em> const char32_t", where <em>n</em> is the size of the string as
defined below; each successive element of the array has the value of the
corresponding code unit of the UTF-32 encoding of the string.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#11">
5.13.5 [lex.string] paragraph 11</a>:<br/>
<em>Drafting Note:</em> The contents of paragraphs 6, 7, 9, 10, and 11 were
incorporated into new paragraphs.
<blockquote class="stddel">
A
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
that begins with <tt>L</tt>, such as <tt>L"asdf"</tt>, is a
<em>wide string literal</em> as its associated character encoding.  A wide
string literal has type "array of <em>n</em> const wchar_t", where <em>n</em>
is the size of the string as defined below; it is initialized with the given
characters.
</blockquote>
</p>

<p>Change in
<a href="http://eel.is/c++draft/lex.string#12">
5.13.5 [lex.string] paragraph 12</a>:
<blockquote>
In
<a href="http://eel.is/c++draft/lex.phases">translation phase 6</a>
(<a href="http://eel.is/c++draft/lex.phases">[lex.phases]</a>),
adjacent
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>s
are concatenated.  If both
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>s
have the same
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix"><em>encoding-prefix</em></a>,
the resulting concatenated string literal has that
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix"><em>encoding-prefix</em></a>.
If one
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
has no
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix"><em>encoding-prefix</em></a>,
it is treated as a
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
of the same
<a href="http://eel.is/c++draft/lex.ccon#nt:encoding-prefix"><em>encoding-prefix</em></a>
as the other operand.  If a UTF-8 string literal token is adjacent to a wide
string literal token, the program is ill-formed.  Any other concatenations are
conditionally-supported with implementation-defined behavior.
[ <em>Note:</em> This concatenation is an interpretation, not a conversion.
Because the interpretation happens in translation phase 6 (<del>after each
character from a string literal has been translated into a value from the
appropriate character set</del><ins>after the string literal contents have been
encoded in the
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>'s
associated character encoding</ins>), a
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a><ins>'</ins>s
initial rawness has no effect on the interpretation or well-formedness of the
concatenation.  &mdash; <em>end note</em> ] Table
<a href="http://eel.is/c++draft/lex.string#tab:lex.string.concat">9</a>
has some examples of valid concatenations.
<div align="center">
<table border="0">
<tr>
<td align="left">Table <a href="http://eel.is/c++draft/lex.string#tab:lex.string.concat">9</a>:
String literal concatenations</td>
<td/>
<td align="right">[tab:lex.string.concat]</td>
</tr>
</table>
<br/>
<table border="1">
<tr>
<td>
  <table>
    <tr><th align="center">Source</th><th align="left">Means</th></tr>
    <tr>
      <td>
        <table>
          <tr><td align="left"><tt>u"a"</tt></td><td align="left"><tt>u"b"</tt></td></tr>
          <tr><td align="left"><tt>u"a"</tt></td><td align="left"><tt>"b"</tt></td></tr>
          <tr><td align="left"><tt>"a"</tt></td><td align="left"><tt>u"b"</tt></td></tr>
        </table>
      </td>
      <td>
        <table>
          <tr><td align="left"><tt>u"ab"</tt></td></tr>
          <tr><td align="left"><tt>u"ab"</tt></td></tr>
          <tr><td align="left"><tt>u"ab"</tt></td></tr>
        </table>
      </td>
    </tr>
  </table>
</td>
<td>
  <table>
    <tr><th align="center">Source</th><th align="left">Means</th></tr>
    <tr>
      <td>
        <table>
          <tr><td align="left"><tt>U"a"</tt></td><td align="left"><tt>U"b"</tt></td></tr>
          <tr><td align="left"><tt>U"a"</tt></td><td align="left"><tt>"b"</tt></td></tr>
          <tr><td align="left"><tt>"a"</tt></td><td align="left"><tt>U"b"</tt></td></tr>
        </table>
      </td>
      <td>
        <table>
          <tr><td align="left"><tt>U"ab"</tt></td></tr>
          <tr><td align="left"><tt>U"ab"</tt></td></tr>
          <tr><td align="left"><tt>U"ab"</tt></td></tr>
        </table>
      </td>
    </tr>
  </table>
</td>
<td>
  <table>
    <tr><th align="center">Source</th><th align="left">Means</th></tr>
    <tr>
      <td>
        <table>
          <tr><td align="left"><tt>L"a"</tt></td><td align="left"><tt>L"b"</tt></td></tr>
          <tr><td align="left"><tt>L"a"</tt></td><td align="left"><tt>"b"</tt></td></tr>
          <tr><td align="left"><tt>"a"</tt></td><td align="left"><tt>L"b"</tt></td></tr>
        </table>
      </td>
      <td>
        <table>
          <tr><td align="left"><tt>L"ab"</tt></td></tr>
          <tr><td align="left"><tt>L"ab"</tt></td></tr>
          <tr><td align="left"><tt>L"ab"</tt></td></tr>
        </table>
      </td>
    </tr>
  </table>
</td>
</tr>
</table>
</div>
<br/>
Characters in concatenated strings are kept distinct.<br/><br/>
[ <em>Example:</em>
<div style="margin-left: 1em;">
<pre><code>"\xA" "B"</code></pre>
</div>
contains the two characters <tt>'\xA'</tt> and <tt>'B'</tt> after concatenation
(and not the single hexadecimal character <tt>'\xAB'</tt>).
&mdash; <em>end example</em> ]
</blockquote>
</p>

<p>Change in
<a href="http://eel.is/c++draft/lex.string#13">
5.13.5 [lex.string] paragraph 13</a>:
<blockquote>
After any necessary concatenation, in
<a href="http://eel.is/c++draft/lex.phases">translation phase 7</a>
(<a href="http://eel.is/c++draft/lex.phases">[lex.phases]</a>),
<del><tt>'\0'</tt></del><ins>a null character</ins> is appended to every
string literal so that programs that scan a string can find its end.
</blockquote>
</p>

<p>Delete
<a href="http://eel.is/c++draft/lex.string#14">
5.13.5 [lex.string] paragraph 14</a>:<br/>
<em>Drafting note:</em> This wording has been removed as misleading, incomplete,
or redundant.  String literal contents do not always have the same meaning as in
character literals.  The wording regarding single and double quotes is redundant
with the grammar.  The discussion of string length is unnecessary as string
length is determined by encoding.
<blockquote class="stddel">
Escape sequences and
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>s
in non-raw string literals have the same meaning as in
<a href="http://eel.is/c++draft/lex.ccon">character literals</a>
(<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>), except that
the single quote <tt>'</tt> is representable either by itself or by the escape
sequence <tt>\'</tt>, and the double quote <tt>"</tt> shall be preceded by a
<tt>\</tt>, and except that a
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
in a UTF-16 string literal may yield a surrogate pair.  In a narrow string
literal, a
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
may map to more than one <tt>char</tt> or <tt>char8_t</tt> element due to
<a href="http://eel.is/c++draft/lex.string#def:encoding,multibyte"><em>multibyte encoding</em></a>.
The size of a <tt>char32_t</tt> or wide string
literal is the total number of escape sequences,
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>s,
and other characters, plus one for the terminating <tt>U'\0'</tt> or
<tt>L'\0'</tt>.  The size of a UTF-16 string literal is the total number of
escape sequences,
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>s,
and other characters, plus one for each character requiring a surrogate pair,
plus one for the terminating <tt>u'\0'</tt>.  [ <em>Note:</em> The size of a
<tt>char16_t</tt> string literal is the number of
code units, not the number of characters.  &mdash; <em>end note</em> ] Within
<tt>char32_t</tt> and <tt>char16_t</tt> string literals, any
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>s
shall be within the range <tt>0x0</tt> to <tt>0x10FFFF</tt>.  The size of a
narrow string literal is the total number of escape sequences and other
characters, plus at least one for the multibyte encoding of each
<a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>,
plus one for the terminating <tt>'\0'</tt>.
</blockquote>
</p>

<p>Change in
<a href="http://eel.is/c++draft/lex.string#15">
5.13.5 [lex.string] paragraph 15</a>:<br/>
<em>Drafting note:</em> Wording for string literal object initialization has
been moved to a new paragraph.
<blockquote>
Evaluating a
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
results in a string literal object with static storage duration<ins>
(<a href="http://eel.is/c++draft/basic.stc">[basic.stc]</a>)</ins><del>,
initialized from the given characters as specified above</del>.  Whether all
string literals are distinct (that is, are stored in nonoverlapping objects)
and whether successive evaluations of a
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
yield the same or a different object is unspecified.  [ <em>Note:</em> The
effect of attempting to modify a string literal is undefined.
&mdash; <em>end note</em> ]
</blockquote>
</p>

<p>Add a new paragraph (X) after
<a href="http://eel.is/c++draft/lex.string#15">
5.13.5 [lex.string] paragraph 15</a>:
<blockquote class="stdins">
String literal objects are initialized with the sequence of code unit values
corresponding to the
<a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>'s
sequence of
<a href="http://eel.is/c++draft/lex.string#nt:s-char"><em>s-char</em></a>s
(for a non-raw string literal) and
<a href="http://eel.is/c++draft/lex.string#nt:r-char"><em>r-char</em></a>s
(for a raw string literal) after
<a href="http://eel.is/c++draft/lex.phases#1.7">translation phase 7</a>
(<a href="http://eel.is/c++draft/lex.phases">[lex.phases]</a>) as follows.
<table>
  <tr>
    <td>(X.1)&nbsp;&mdash;</td>
    <td>
      The characters denoted by each
      <a href="http://eel.is/c++draft/lex.string#nt:basic-s-char"><em>basic-s-char</em></a>,
      <a href="http://eel.is/c++draft/lex.string#nt:r-char"><em>r-char</em></a>,
      <a href="http://eel.is/c++draft/lex.ccon#nt:character-escape-sequence"><em>character-escape-sequence</em></a>
      (<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>), and
      <a href="http://eel.is/c++draft/lex.charset#nt:universal-character-name"><em>universal-character-name</em></a>
      (<a href="http://eel.is/c++draft/lex.charset">[lex.charset]</a>)
      are encoded to a code unit sequence using the
      <a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>'s
      associated character encoding.  If a character lacks representation in the
      associated character encoding, then, for an
      <em>ordinary string literal</em> or a <em>wide string literal</em>, the
      <a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
      is conditionally-supported and an implementation defined code unit
      sequence is encoded; otherwise, the
      <a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
      is ill-formed.
    </td>
  </tr>
  <tr>
    <td>(X.2)&nbsp;&mdash;</td>
    <td>
      Each
      <a href="http://eel.is/c++draft/lex.ccon#nt:numeric-escape-sequence"><em>numeric-escape-sequence</em></a>
      (<a href="http://eel.is/c++draft/lex.ccon">[lex.ccon]</a>)
      contributes a single code unit value with the numeric value of the octal or
      hexadecimal number.  There is no limit to the number of digits in a hexadecimal
      sequence.  A sequence of octal or hexadecimal digits is terminated by the first
      character that is not an octal digit or a hexadecimal digit, respectively. If
      the numeric value exceeds the range of the
      <a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>'s
      code unit type, then, for an <em>ordinary string literal</em> or a
      <em>wide string literal</em>, an implementation-defined code unit value
      is encoded; otherwise, the
      <a href="http://eel.is/c++draft/lex.string#nt:string-literal"><em>string-literal</em></a>
      is ill-formed.
    </td>
  </tr>
</table>
</blockquote>
</p>


</body>
