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Re: detecting incomplete type

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On Wednesday, February 6, 2013 7:50:31 AM UTC, Balog Pal wrote:
> What is a standard way to tell whether a type is complete or not? In a
> way usable in say static_assert?

> In boost code I saw sizeof(T) used that worked fine on gcc and msvc
> which make that 0. But I recently read the section on sizeof that
> tells it used with incomplete type makes the program ill-formed.

SFINAE should help here.  Something along the lines of:

    template <typename T>
    class Derived : public T {};

    TrueType discrim( Derived<T>* );
    FalseTpe discrim( ... );

and then something like `sizeof( discrim<T>( 0 ) )`.  If the
type is incomplete, the instantiation of Derived<T> fails,

--
James


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detecting incomplete type Balog Pal <pasa@lib.hu> - 2013-02-06 01:50 -0600
  Re: detecting incomplete type Daniel Krügler <daniel.kruegler@googlemail.com> - 2013-02-07 02:08 -0600
  Re: detecting incomplete type James Kuyper <jameskuyper@verizon.net> - 2013-02-07 02:31 -0600
  Re: detecting incomplete type James Kanze <james.kanze@googlemail.com> - 2013-02-07 02:32 -0600

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