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    CWG Issue 1122</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="1122"></A><H4>1122.
  
Circular definition of <TT>std::size_t</TT>
</H4>
<B>Section: </B>7.6.2.5&#160; [<A href="https://wg21.link/expr.sizeof">expr.sizeof</A>]
 &#160;&#160;&#160;

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

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

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


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

<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3296.html#GB24">N3092 comment
  GB&#160;24<BR></A>

<P>The return type of the <TT>sizeof</TT> operator is
defined as being of type <TT>std::size_t</TT>, defined in
library 17.2 [<A href="https://wg21.link/support.types">support.types</A>]. This, in turn,
says that <TT>size_t</TT> is defined in the C standard,
which in turn says that <TT>size_t</TT> is defined as the
type of the result of the <TT>sizeof</TT> operator!</P>

<P>The C definition of <TT>sizeof</TT> returns an
implementation-defined unsigned integer type, recommended
not to have &#8220;an integer conversion rank greater than
<TT>signed long int</TT>, unless the implementation supports
objects large enough to make this necessary.&#8221;</P>

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

<P>Add the following three paragraphs after 17.2 [<A href="https://wg21.link/support.types#4">support.types</A>] paragraph 4:
</P>

<BLOCKQUOTE>

<P>The type <TT>ptrdiff_t</TT> is an implementation-defined signed
integer type that can hold the difference of two subscripts in an
array object, as described in 7.6.6 [<A href="https://wg21.link/expr.add">expr.add</A>].</P>

<P>The type <TT>size_t</TT> is an implementation-defined unsigned
integer type that is large enough to contain the size in bytes of any
object.</P>

<P>[<I>Note:</I> It is recommended that implementations choose types
for <TT>ptrdiff_t</TT> and <TT>size_t</TT> whose integer conversion
ranks (7.3.15 [<A href="https://wg21.link/conv.bool">conv.bool</A>]) are no greater than that of <TT>signed
long int</TT> unless a larger size is necessary to contain all the possible
values. &#8212;<I>end note</I>] </P>

</BLOCKQUOTE>

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