gcc/testsuite/g++.dg/cpp2a/constexpr-new28.C


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// PR c++/115645
// { dg-do compile { target c++20 } }

using size_t = decltype(sizeof(0));

void* operator new(size_t, void* p) { return p; }
void* operator new[](size_t, void* p) { return p; }

#define VERIFY(C) if (!(C)) throw

namespace std {
  template<typename T>
    constexpr T* construct_at(T* p)
    {
      if constexpr (__is_array(T))
        return ::new((void*)p) T[1]();
      else
        return ::new((void*)p) T();
    }
}

struct S {
  constexpr S () : s (0) {}
  constexpr S (int x) : s (x) {}
  constexpr bool operator== (int x) const { return s == x; }
  int s;
};

constexpr void
test_array()
{
  S arr[1] { 99 };
  std::construct_at(&arr);
  VERIFY( arr[0] == 0 );

  union U {
    long long x = -1;
    S arr[4];
  } u;

  auto p = std::construct_at(&u.arr);
  VERIFY( (*p)[0] == 0 );
}

static_assert( [] { test_array(); return true; }() );