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    CWG Issue 630</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="630"></A><H4>630.
  
Equality of narrow and wide character values in the basic character set
</H4>
<B>Section: </B>5.3.1&#160; [<A href="https://wg21.link/lex.charset">lex.charset</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD2
 &#160;&#160;&#160;

 <B>Submitter: </B>Tom Plum
 &#160;&#160;&#160;

 <B>Date: </B>21 April 2007<BR>


<P>[Voted into WP at October, 2009 meeting.]</P>

<P>WG14 accepted
<A href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_279.htm">
DR 279</A> regarding the rule known colloquially as the
<TT>L'x'=='x'</TT> rule.  This change was made to C99 in TC2.  The
Austin Group subsequently opened
<A href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_321.htm">
DR 321</A> against TC2, observing that the change made in TC2 would
invalidate existing conforming C code that relied on the
<TT>L'x'=='x'</TT> rule.</P>

<P>DR 321 is now closed and will be included in the CD3 to C99.  This
change defines a new standard macro, which WG14 drafted as follows:</P>

<BLOCKQUOTE>

<TT>__STDC_MB_MIGHT_NEQ_WC__</TT>: The integer constant <TT>1</TT>,
intended to indicate that there might be some
character <TT>x</TT> in the basic character set, such
that <TT>'x'</TT> need not be equal to <TT>L'x'</TT>.

</BLOCKQUOTE>

<P>WG14 requests that WG21 adopt this revision and this macro in
C++0x.</P>

<P><B>Proposed resolution (July, 2009):</B></P>

<P>Add the following to 15.12 [<A href="https://wg21.link/cpp.predefined#2">cpp.predefined</A>] paragraph 2:</P>

<BLOCKQUOTE>

<DL>
<DT><INS><TT>__STDC_MB_MIGHT_NEQ_WC__</TT></INS></DT>

<DD><INS>The integer constant <TT>1</TT>, intended to indicate that,
in the encoding for <TT>wchar_t</TT>, a member of the basic character
set need not have a code value equal to its value when used as the
lone character in an ordinary character literal.</INS></DD>

</DL>

</BLOCKQUOTE>

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