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    CWG Issue 1125</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="1125"></A><H4>1125.
  
Unclear definition of &#8220;potential constant expression&#8221;
</H4>
<B>Section: </B>7.7&#160; [<A href="https://wg21.link/expr.const">expr.const</A>]
 &#160;&#160;&#160;

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

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

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


<P>[Voted into the WP at the November, 2010 meeting as paper N3218.]</P>

<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3296.html#DE8">N3092 comment
  DE&#160;8<BR></A>

<P>In the definition of &#8220;potential constant
expression&#8221; in 7.7 [<A href="https://wg21.link/expr.const#6">expr.const</A>] paragraph 6,
it is unclear how &#8220;arbitrary&#8221; the substitution of the
function parameters is. Does it mean &#8220;there exists a value
for which the result is a constant expression&#8221; or does it
mean &#8220;for all possible values, the result needs to be a
constant expression?&#8221; Example:</P>

<PRE>
    constexpr int f(int x){ return x + 1; }
</PRE>

<P>is a constant expression under the first interpretation,
but not under the second (because overflow occurs for <TT>x
== INT_MAX</TT>, cf 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2
bullet 5). The answer also affects expressions such as:</P>

<PRE>
    constexpr int f2(bool v) { return v ? throw 0 : 0; }
    constexpr int f3(bool v) { return v &amp;&amp; (throw 0, 0); }
</PRE>

<P>See also <A HREF="1129.html">issue 1129</A>.</P>

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