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    CWG Issue 1107</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="1107"></A><H4>1107.
  
Overload resolution for user-defined integer literals
</H4>
<B>Section: </B>5.13.9&#160; [<A href="https://wg21.link/lex.ext">lex.ext</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++11
 &#160;&#160;&#160;

 <B>Submitter: </B>US
 &#160;&#160;&#160;

 <B>Date: </B>2010-08-02<BR><BR>


<P>[Voted into the WP at the November, 2010 meeting.]</P>

<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3296.html#US17">N3092 comment
  US&#160;17<BR></A>

<P>In general, the parameter type of a literal operator must be
the same as the argument passed to it. That is not the
case for a <I>user-defined-character-literal</I>, where the
argument could inadvertently match a literal operator
intended for use with <I>user-defined-integer-literal</I>s:</P>

<PRE>
    typedef unsigned long long ULL;
    int operator "" X(ULL);
    int i = 'c'X; // operator"" X(ULL('c'))
</PRE>

<P>
<U>Suggested resolution</U>:
Add the following phrase to the description in
paragraph 6:</P>

<BLOCKQUOTE>

<I>S</I> shall contain a literal operator whose parameter
type is the same as the type of <I>ch</I>.

</BLOCKQUOTE>

<P><B>Proposed resolution (August, 2010):</B></P>

<P>Change 5.13.9 [<A href="https://wg21.link/lex.ext#6">lex.ext</A>] paragraph 6 as follows:</P>

<BLOCKQUOTE>

If <I>L</I> is a <I>user-defined-character-literal</I>, let <I>ch</I>
be the literal without its <I>ud-suffix</I>. <DEL>The</DEL>
<INS><I>S</I> shall contain a literal operator (12.6 [<A href="https://wg21.link/over.literal">over.literal</A>]) whose only parameter has the type of <I>ch</I> and
the</INS> literal <I>L</I> is treated as a call of the form

<PRE>
    operator "" X (<SPAN CLASS="cmnt">ch</SPAN><DEL> </DEL>)
</PRE>

</BLOCKQUOTE>

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