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    CWG Issue 2695</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="2695"></A><H4>2695.
  
Semantic ignorability of attributes
</H4>
<B>Section: </B>9.13.1&#160; [<A href="https://wg21.link/dcl.attr.grammar">dcl.attr.grammar</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Timur Doumler
 &#160;&#160;&#160;

 <B>Date: </B>2023-02-09<BR>


<P>[Accepted as a DR at the February, 2023 meeting.]</P>

<P>EWG resolved to reflect the understanding of semantic ignorability
of attributes in a note.</P>

<P><B>Proposed resolution (approved by CWG 2023-02-09):</B></P>

<P>Add to 9.13.1 [<A href="https://wg21.link/dcl.attr.grammar#6">dcl.attr.grammar</A>] paragraph 6 as follows:</P>

<BLOCKQUOTE>

[<I>Note 4:</I> A program is ill-formed if it contains an attribute
specified in 9.13 [<A href="https://wg21.link/dcl.attr">dcl.attr</A>] that violates the rules
specifying to which entity or statement the attribute can apply or the
syntax rules for the attribute's <I>attribute-argument-clause</I>, if
any.  &#8212;<I>end note</I>]

<INS>[<I>Note:</I> The <I>attribute</I>s specified in
9.13 [<A href="https://wg21.link/dcl.attr">dcl.attr</A>] have optional semantics: given a well-formed
program, removing all instances of any one of those <I>attribute</I>s
results in a program whose set of possible executions
(4.1.2 [<A href="https://wg21.link/intro.abstract">intro.abstract</A>]) for a given input is a subset of those of
the original program for the same input, absent implementation-defined
guarantees with respect to that <I>attribute</I>. -- end note ]</INS>

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