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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110167] excessive compile time when optimizing
 std::to_array
Date: Thu, 08 Jun 2023 09:51:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110167

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-08
           Keywords|                            |compile-time-hog
             Status|UNCONFIRMED                 |NEW
          Component|libstdc++                   |c++

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

template<unsigned long N>
struct array
{
  int data[N];
};

template<unsigned long...> struct seq { };


template<unsigned long... Idx>
array<sizeof...(Idx)>
to_array_impl(int (&a)[sizeof...(Idx)], seq<Idx...>)
{
  return {{a[Idx]...}};
}


template<unsigned long N>
array<N>
to_array(int (&a)[N])
{
  return to_array_impl(a, seq<__integer_pack(N)...>{});
}

int f[262144];

auto g(void) { return to_array(f); }=