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    CWG Issue 2427</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="2427"></A><H4>2427.
  
Deprecation of volatile operands and unevaluated contexts
</H4>
<B>Section: </B>7.6.19&#160; [<A href="https://wg21.link/expr.assign">expr.assign</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++20
 &#160;&#160;&#160;

 <B>Submitter: </B>Mike Miller
 &#160;&#160;&#160;

 <B>Date: </B>2019-08-14<BR>


<P>[Adopted as a DR at the November, 2019 meeting.]</P>

<P>According to 7.6.19 [<A href="https://wg21.link/expr.assign#7">expr.assign</A>] paragraph 7,</P>

<BLOCKQUOTE>

A simple assignment whose left operand is of a volatile
-qualified non-class type is deprecated
(D.4 [<A href="https://wg21.link/depr.volatile.type">depr.volatile.type</A>]) unless the assignment is either a
discarded-value expression or appears in an unevaluated
context.

</BLOCKQUOTE>

<P>The deprecations of increment, decrement, and compound
assignment operators do not, but presumably should, mention
unevaluated contexts.</P>

<P><B>Notes from the August, 2019 teleconference:</B></P>

<P>The omission of those operators was intentional; the deprecation
is intended only to affect cases where using the result of the
operation would result in a subsequent fetch of the value. However,
some shortcomings of the existing wording were noted and will be
addressed in the resolution.</P>

<P><B>Proposed resolution (October, 2019):</B></P>

<P>Change 7.6.19 [<A href="https://wg21.link/expr.assign#5">expr.assign</A>] paragraph 5 as follows:</P>

<BLOCKQUOTE>

A simple assignment whose left operand is of
a <TT>volatile</TT>-qualified type is deprecated
(D.4 [<A href="https://wg21.link/depr.volatile.type">depr.volatile.type</A>]) unless the <INS>(possibly
parenthesized)</INS> assignment is <DEL>either</DEL>
a discarded-value expression or <DEL>appears in</DEL>
an unevaluated <DEL>context</DEL> <INS>operand</INS>.

</BLOCKQUOTE>

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