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    CWG Issue 2796</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="2796"></A><H4>2796.
  
Function pointer conversions for relational operators
</H4>
<B>Section: </B>7.6.9&#160; [<A href="https://wg21.link/expr.rel">expr.rel</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD7
 &#160;&#160;&#160;

 <B>Submitter: </B>Alisdair Meredith
 &#160;&#160;&#160;

 <B>Date: </B>2023-09-14<BR>


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

<P>Consider:</P>

<PRE>
  void f() {}
  void g() noexcept {}

  void q() {
    bool b1 = f == g;     // <SPAN CLASS="cmnt">OK</SPAN>
    bool b2 = f &gt; g;      // <SPAN CLASS="cmnt">error: different types</SPAN>
  }
</PRE>

<P>For the equality operators, 7.6.10 [<A href="https://wg21.link/expr.eq#3">expr.eq</A>] paragraph 3
specifies:</P>

<BLOCKQUOTE>

If at least one of the operands is a pointer, pointer conversions
(7.3.12 [<A href="https://wg21.link/conv.ptr">conv.ptr</A>]), function pointer conversions
(7.3.14 [<A href="https://wg21.link/conv.fctptr">conv.fctptr</A>]), and qualification conversions
(7.3.6 [<A href="https://wg21.link/conv.qual">conv.qual</A>]) are performed on both operands to bring
them to their composite pointer type
(7.2.2 [<A href="https://wg21.link/expr.type">expr.type</A>]). Comparing pointers is defined as
follows: ...

</BLOCKQUOTE>

<P>In contrast, the corresponding rule for relational operators in
7.6.9 [<A href="https://wg21.link/expr.rel#3">expr.rel</A>] paragraph 3 specifies:</P>

<BLOCKQUOTE>

The usual arithmetic conversions (7.4 [<A href="https://wg21.link/expr.arith.conv">expr.arith.conv</A>]) are
performed on operands of arithmetic or enumeration type. If both
operands are pointers, pointer conversions
(7.3.12 [<A href="https://wg21.link/conv.ptr">conv.ptr</A>]) and qualification conversions
(7.3.6 [<A href="https://wg21.link/conv.qual">conv.qual</A>]) are performed to bring them to their
composite pointer type (7.2.2 [<A href="https://wg21.link/expr.type">expr.type</A>]). After
conversions, the operands shall have the same type.

</BLOCKQUOTE>

<P>However, all major implementations accept the example.</P>

<P><B>Proposed resolution (approved by CWG 2023-10-06):</B></P>

<P>Change in 7.6.9 [<A href="https://wg21.link/expr.rel#3">expr.rel</A>] paragraph 3 as follows:</P>

<BLOCKQUOTE>

The usual arithmetic conversions (7.4 [<A href="https://wg21.link/expr.arith.conv">expr.arith.conv</A>]) are
performed on operands of arithmetic or enumeration type. If both
operands are pointers, pointer conversions
(7.3.12 [<A href="https://wg21.link/conv.ptr">conv.ptr</A>])<INS>, function pointer conversions
(7.3.14 [<A href="https://wg21.link/conv.fctptr">conv.fctptr</A>]),</INS> and qualification conversions
(7.3.6 [<A href="https://wg21.link/conv.qual">conv.qual</A>]) are performed to bring them to their
composite pointer type (7.2.2 [<A href="https://wg21.link/expr.type">expr.type</A>]). After
conversions, the operands shall have the same type.

</BLOCKQUOTE>

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