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    CWG Issue 956</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="956"></A><H4>956.
  
Function prototype scope with late-specified return types
</H4>
<B>Section: </B>9.3.4.6&#160; [<A href="https://wg21.link/dcl.fct">dcl.fct</A>]
 &#160;&#160;&#160;

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

 <B>Submitter: </B>Daveed Vandevoorde
 &#160;&#160;&#160;

 <B>Date: </B>21 August, 2009<BR>


<P>[Voted into WP at March, 2010 meeting.]</P>

<P>According to 6.4.4 [<A href="https://wg21.link/basic.scope.param#1">basic.scope.param</A>] paragraph 1,</P>

<BLOCKQUOTE>

In a function declaration, or in any function declarator except the
declarator of a function definition (9.6 [<A href="https://wg21.link/dcl.fct.def">dcl.fct.def</A>]), names of
parameters (if supplied) have function prototype scope, which
terminates at the end of the nearest enclosing function declarator.

</BLOCKQUOTE>

<P>Happily, this permits the use of parameter names with <TT>decltype</TT>
in a late-specified return type, because the return type is part of the
function's declarator.  However, the note in 9.3.4.6 [<A href="https://wg21.link/dcl.fct#11">dcl.fct</A>] paragraph 11
is now inaccurate and should be updated:</P>

<BLOCKQUOTE>

[<I>Note:</I> ...If a parameter name is present in a function
declaration that is not a definition, it cannot be used outside of the
<I>parameter-declaration-clause</I> since it goes out of scope at the
end of the function declarator (6.4 [<A href="https://wg21.link/basic.scope">basic.scope</A>]). &#8212;<I>end note</I>]

</BLOCKQUOTE>

<P><B>Proposed resolution (February, 2010):</B></P>

<P>Change the note in 9.3.4.6 [<A href="https://wg21.link/dcl.fct#10">dcl.fct</A>] paragraph 10 as follows:</P>

<BLOCKQUOTE>

...[<I>Note:</I> in particular, parameter names are also optional in
function definitions and names used for a parameter in different
declarations and the definition of a function need not be the
same.  If a parameter name is present in a function declaration
that is not a definition, it cannot be used outside of <DEL>the
<I>parameter-declaration-clause</I> since it goes out of scope at
the end of the function declarator (6.4 [<A href="https://wg21.link/basic.scope">basic.scope</A>])</DEL> <INS>its function declarator because that is
the extent of its potential scope (6.4.4 [<A href="https://wg21.link/basic.scope.param">basic.scope.param</A>])</INS>. &#8212;<I>end note</I>]

</BLOCKQUOTE>

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