// C++N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf
#define msg "C++N4606(235)18.6.3 Storage allocation errors [alloc.errors]18.6.3.1 Class bad_alloc[bad.alloc]p504.cpp"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <iostream>
#include <cstdlib>
#include <new>

int main() {

  struct X {
    const int n;
  };
  X *p = new X{3};
  const int a = p->n;
  new (p) X{5}; // p does not point to new object (3.8)
// because X::n is const
  const int b = p->n; // undefined behavior
  const int c = std::launder(p)->n; // OK
  std::cout<< "c=" <<c<< " a=" <<a<< std::endl;
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppall.sh p505
$ clang++ p505.cpp -std=c++03 -Wall
p505.cpp:12:8: error: implicit default constructor for 'X' must explicitly initialize the const member 'n'
struct X { const int n; };
       ^
p505.cpp:13:12: note: in implicit default constructor for 'X' first required here
X *p = new X{3};
           ^
p505.cpp:12:22: note: declared here
struct X { const int n; };
                     ^
p505.cpp:13:13: error: expected ';' at end of declaration
X *p = new X{3};
            ^
            ;
p505.cpp:15:9: error: no matching constructor for initialization of 'X'
new (p) X{5}; // p does not point to new object (3.8)
        ^
p505.cpp:12:8: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 0 were provided
struct X { const int n; };
       ^
p505.cpp:18:20: error: no member named 'launder' in namespace 'std'; did you mean '__launder'?
const int c = std::launder(p)->n; // OK
              ~~~~~^~~~~~~
                   __launder
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/new:257:24: note: '__launder' declared here
_LIBCPP_CONSTEXPR _Tp* __launder(_Tp* __p) _NOEXCEPT
                       ^
4 errors generated.
$ clang++ p505.cpp -std=c++11 -Wall
p505.cpp:18:20: error: no member named 'launder' in namespace 'std'; did you mean '__launder'?
const int c = std::launder(p)->n; // OK
              ~~~~~^~~~~~~
                   __launder
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/new:257:24: note: '__launder' declared here
_LIBCPP_CONSTEXPR _Tp* __launder(_Tp* __p) _NOEXCEPT
                       ^
1 error generated.
$ clang++ p505.cpp -std=c++17 -Wall
p505.cpp:17:11: warning: unused variable 'b' [-Wunused-variable]
const int b = p->n; // undefined behavior
          ^
1 warning generated.
c=5 a=3
C++N4606(235)18.6.3 Storage allocation errors [alloc.errors]18.6.3.1 Class bad_alloc[bad.alloc]p504.cpp

$ g++-7 p505.cpp -std=c++03  -Wall
p505.cpp: In function 'int main()':
p505.cpp:13:13: warning: extended initializer lists only available with -std=c++11 or -std=gnu++11
 X *p = new X{3};
             ^
p505.cpp:15:10: warning: extended initializer lists only available with -std=c++11 or -std=gnu++11
 new (p) X{5}; // p does not point to new object (3.8)
          ^
p505.cpp:18:20: error: 'launder' is not a member of 'std'
 const int c = std::launder(p)->n; // OK
                    ^~~~~~~
p505.cpp:17:11: warning: unused variable 'b' [-Wunused-variable]
 const int b = p->n; // undefined behavior
           ^

$ g++-7 p505.cpp -std=c++11  -Wall
p505.cpp: In function 'int main()':
p505.cpp:18:20: error: 'launder' is not a member of 'std'
 const int c = std::launder(p)->n; // OK
                    ^~~~~~~
p505.cpp:17:11: warning: unused variable 'b' [-Wunused-variable]
 const int b = p->n; // undefined behavior
           ^

$ g++-7 p505.cpp -std=c++17  -Wall
p505.cpp: In function 'int main()':
p505.cpp:17:11: warning: unused variable 'b' [-Wunused-variable]
 const int b = p->n; // undefined behavior
           ^
c=5 a=3
C++N4606(235)18.6.3 Storage allocation errors [alloc.errors]18.6.3.1 Class bad_alloc[bad.alloc]p504.cpp