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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/113841] Can't swap two std::hash<T*>
Date: Fri, 01 Mar 2024 18:24:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113841

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This one's much harder to fix:

#include <string>

template<typename T>
struct Alloc
{
  using value_type =3D T;

  Alloc(int) { }

  template<typename U> Alloc(const Alloc<U>&) { }

  T* allocate(std::size_t n) { return std::allocator<T>().allocate(n); }
  void deallocate(T* p, std::size_t n) { std::allocator<T>().deallocate(p, =
n);
}
};

template<typename T> struct wrap { T t; };

template<typename T> void do_adl(T&) { }

void test_pr113841()
{
  using Tr =3D std::char_traits<char>;
  using test_type =3D std::basic_string<char, Tr, Alloc<char>>;
  std::pair<const int, wrap<test_type>>* h =3D nullptr;
  do_adl(h);
}=