clang/test/AST/ByteCode/cxx14.cpp

// RUN: %clang_cc1 -std=c++14 -verify=both,expected %s -fexperimental-new-constant-interpreter
// RUN: %clang_cc1 -std=c++14 -verify=both,ref      %s



constexpr int(*null_ptr)() = nullptr;
constexpr int test4 = (*null_ptr)(); // both-error {{must be initialized by a constant expression}} \
                                     // both-note {{evaluates to a null function pointer}}

struct E {
  int n = 0;
  struct {
    void *x = this;
  };
  void *y = this;
};
constexpr E e1 = E();
static_assert(e1.x != e1.y, "");
constexpr E e2 = E{0};
static_assert(e2.x != e2.y, "");

struct S {
  int &&a = 2;
  int b[1]{a};
};
constexpr int foo() {
  S s{12};
  return s.b[0];
}
static_assert(foo() == 12, "");

int arr[3]; // both-note {{declared here}}
constexpr bool f() { // both-error {{constexpr function never produces a constant expression}}
  int &r  = arr[3]; // both-note {{read of dereferenced one-past-the-end pointer}} \
                    // both-warning {{array index 3 is past the end of the array}}
  return true;
}

namespace InitListModify {
  struct Aggregate {
    int x = 0;
    int y = ++x;
  };
  constexpr Aggregate aggr1;
  static_assert(aggr1.x == 1 && aggr1.y == 1, "");
  // This is not specified by the standard, but sanity requires it.
  constexpr Aggregate aggr2 = {};
  static_assert(aggr2.x == 1 && aggr2.y == 1, "");
}

namespace UnionTrivialCopy {
  struct A {
    constexpr A() {}
    struct B {
      union U {
        constexpr U() : y(4) {}
        int x;
        int y;
      } u;
    } b;
  };
  constexpr int testA() {
    A a, b;
    a.b.u.y = 5;
    b = a;
    return b.b.u.y;
  }
  static_assert(testA() == 5, "");
}