text: // RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify=expected,cxx11 -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu
  // RUN: %clang_cc1 -fsyntax-only -std=c++2a -pedantic -verify=expected,cxx20 -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu
  
  // A conditional-expression is a core constant expression unless it involves one
  // of the following as a potentially evaluated subexpression [...]:
  
  // - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant
  //   expression, function invocation substitution (7.1.5 [dcl.constexpr])
  //   replaces each occurrence of this in a constexpr member function with a
  //   pointer to the class object. -end note];
  struct This {
    int this1 : this1; // expected-error {{undeclared}}
    int this2 : this->this1; // expected-error {{invalid}}
    void this3() {
      int n1[this->this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
      int n2[this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
      (void)n1, (void)n2;
    }
  };
  
  // - an invocation of a function other than a constexpr constructor for a
  //   literal class or a constexpr function [ Note: Overload resolution (13.3)
  //   is applied as usual - end note ];
  struct NonConstexpr1 {
    static int f() { return 1; } // expected-note {{here}}
    int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
  };
  struct NonConstexpr2 {
    constexpr NonConstexpr2(); // expected-note {{here}}
    int n;
  };
  struct NonConstexpr3 {
    NonConstexpr3();
    int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
  };
  struct NonConstexpr4 {
    NonConstexpr4();
    int n;
  };
  struct NonConstexpr5 {
    int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-literal type 'NonConstexpr4' cannot be used in a constant expression}}
  };
  
  // - an invocation of an undefined constexpr function or an undefined
  //   constexpr constructor;
  struct UndefinedConstexpr {
    constexpr UndefinedConstexpr();
    static constexpr int undefinedConstexpr1(); // expected-note {{here}}
    int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}}
  };
  
  // - an invocation of a constexpr function with arguments that, when substituted
  //   by function invocation substitution (7.1.5), do not produce a core constant
  //   expression;
  namespace NonConstExprReturn {
    static constexpr const int &id_ref(const int &n) {
      return n;
    }
    struct NonConstExprFunction {
      int n : id_ref(16); // ok
    };
    constexpr const int *address_of(const int &a) {
      return &a;
    }
    constexpr const int *return_param(int n) {
      return address_of(n);
    }
    struct S {
      int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of object outside its lifetime}}
    };
  }
  
  // - an invocation of a constexpr constructor with arguments that, when
  //   substituted by function invocation substitution (7.1.5), do not produce all
  //   constant expressions for the constructor calls and full-expressions in the
  //   mem-initializers (including conversions);
  namespace NonConstExprCtor {
    struct T {
      constexpr T(const int &r) :
        r(r) {
      }
      const int &r;
    };
    constexpr int n = 0;
    constexpr T t1(n); // ok
    constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{reference to temporary is not a constant expression}}
  
    struct S {
      int n : T(4).r; // ok
    };
  }
  
  // - an invocation of a constexpr function or a constexpr constructor that would
  //   exceed the implementation-defined recursion limits (see Annex B);
  namespace RecursionLimits {
    constexpr int RecurseForever(int n) {
      return n + RecurseForever(n+1); // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'RecurseForever(}} expected-note {{skipping 118 calls}}
    }
    struct AlsoRecurseForever {
      constexpr AlsoRecurseForever(int n) :
        n(AlsoRecurseForever(n+1).n) // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'AlsoRecurseForever(}} expected-note {{skipping 118 calls}}
      {}
      int n;
    };
    struct S {
      int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
      int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
    };
  }
  
  // DR1458: taking the address of an object of incomplete class type
  namespace IncompleteClassTypeAddr {
    struct S;
    extern S s;
    constexpr S *p = &s; // ok
    static_assert(p, "");
  
    extern S sArr[];
    constexpr S (*p2)[] = &sArr; // ok
  
    struct S {
      constexpr S *operator&() const { return nullptr; }
    };
    constexpr S *q = &s; // ok
    static_assert(!q, "");
  }
  
  // - an operation that would have undefined behavior [Note: including, for
  //   example, signed integer overflow (Clause 5 [expr]), certain pointer
  //   arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
  //   shift operations (5.8 [expr.shift]) -end note];
  namespace UndefinedBehavior {
    void f(int n) {
      switch (n) {
      case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
      case (int)0x80000000u: // ok
      case (int)10000000000ll: // expected-note {{here}}
      case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
      case (int)(unsigned)(long long)4.4e9: // ok
      case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
      case (int)((float)1e37 / 1e30): // ok
      case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
        break;
      }
    }
  
    constexpr int int_min = ~0x7fffffff;
    constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
    constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}}
    constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}}
    constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
    constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
  
    constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
    constexpr int shl_0 = 0 << 0; // ok
    constexpr int shl_31 = 0 << 31; // ok
    constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}}
    constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
    constexpr int shl_unsigned_into_sign = 1u << 31; // ok
    constexpr int shl_unsigned_overflow = 1024u << 31; // ok
    constexpr int shl_signed_negative = (-3) << 1; // cxx11-error {{constant expression}} cxx11-note {{left shift of negative value -3}}
    constexpr int shl_signed_ok = 1 << 30; // ok
    constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
    constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
    constexpr int shl_signed_off_end = 2 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}}
    constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}}
    constexpr int shl_signed_overflow = 1024 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{requires 43 bits to represent}}
    constexpr int shl_signed_ok2 = 1024 << 20; // ok
  
    constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
    constexpr int shr_0 = 0 >> 0; // ok
    constexpr int shr_31 = 0 >> 31; // ok
    constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}}
  
    struct S {
      int m;
    };
    constexpr S s = { 5 };
    constexpr const int *p = &s.m + 1;
    constexpr const int &f(const int *q) {
      return q[0];
    }
    constexpr int n = (f(p), 0); // ok
    struct T {
      int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
    };
  
    namespace Ptr {
      struct A {};
      struct B : A { int n; };
      B a[3][3];
      constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
      B b = {};
      constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
      constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
      constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
      constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
  
      constexpr A *na = nullptr;
      constexpr B *nb = nullptr;
      constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
      constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
      static_assert((A*)nb == 0, "");
      static_assert((B*)na == 0, "");
      constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
      constexpr const int *np1 = (int*)nullptr + 0; // ok
      constexpr const int *np2 = &(*(int(*)[4])nullptr)[0]; // ok
      constexpr const int *np3 = &(*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot perform pointer arithmetic on null pointer}}
  
      struct C {
        constexpr int f() const { return 0; }
      } constexpr c = C();
      constexpr int k1 = c.f(); // ok
      constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced null pointer}}
      constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced one-past-the-end pointer}}
      C c2;
      constexpr int k4 = c2.f(); // ok!
  
      constexpr int diff1 = &a[2] - &a[0];
      constexpr int diff2 = &a[1][3] - &a[1][0];
      constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
      static_assert(&a[2][0] == &a[1][3], "");
      constexpr int diff4 = (&b + 1) - &b;
      constexpr int diff5 = &a[1][2].n - &a[1][0].n; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
      constexpr int diff6 = &a[1][2].n - &a[1][2].n;
      constexpr int diff7 = (A*)&a[0][1] - (A*)&a[0][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
    }
  
    namespace Overflow {
      // Signed int overflow.
      constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
      constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
      constexpr int n3 = n1 + 1; // ok
      constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
      constexpr int n5 = -65536 * 32768; // ok
      constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
      constexpr int n7 = -n3 + -1; // ok
      constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
      constexpr int n9 = n3 - 0; // ok
      constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
      constexpr int n11 = -1 - n3; // ok
      constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
      constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
      constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
      constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
      constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
      constexpr signed char c2 = '\x64' * '\2'; // also ok  expected-warning{{changes value}}
      constexpr long long ll1 = 0x7fffffffffffffff; // ok
      constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
      constexpr long long ll3 = -ll1 - 1; // ok
      constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
      constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
  
      // Yikes.
      char melchizedek[2200000000];
      typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
      constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
      constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
      constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
      constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
  
      // Unsigned int overflow.
      static_assert(65536u * 65536u == 0u, ""); // ok
      static_assert(4294967295u + 1u == 0u, ""); // ok
      static_assert(0u - 1u == 4294967295u, ""); // ok
      static_assert(~0u * ~0u == 1u, ""); // ok
  
      template<typename T> constexpr bool isinf(T v) { return v && v / 2 == v; }
  
      // Floating-point overflow and NaN.
      constexpr float f1 = 1e38f * 3.4028f; // ok
      constexpr float f2 = 1e38f * 3.4029f; // ok, +inf is in range of representable values
      constexpr float f3 = 1e38f / -.2939f; // ok
      constexpr float f4 = 1e38f / -.2938f; // ok, -inf is in range of representable values
      constexpr float f5 = 2e38f + 2e38f; // ok, +inf is in range of representable values
      constexpr float f6 = -2e38f - 2e38f; // ok, -inf is in range of representable values
      constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
      constexpr float f8 = 1.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
      constexpr float f9 = 1e308 / 1e-308; // ok, +inf
      constexpr float f10 = f2 - f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
      constexpr float f11 = f2 + f4; // expected-error {{constant expression}} expected-note {{produces a NaN}}
      constexpr float f12 = f2 / f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
  #pragma float_control(push)
  #pragma float_control(except, on)
  constexpr float pi = 3.14f;
  constexpr unsigned ubig = 0xFFFFFFFF;
  constexpr float ce = 1.0 / 3.0; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
  constexpr int ci = (int) pi;
  constexpr float fbig = (float) ubig; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
  constexpr float fabspi = __builtin_fabs(pi); // no error expected
  constexpr float negpi = -pi; // expect no error on unary operator
  #pragma float_control(pop)
      static_assert(!isinf(f1), "");
      static_assert(isinf(f2), "");
      static_assert(!isinf(f3), "");
      static_assert(isinf(f4), "");
      static_assert(isinf(f5), "");
      static_assert(isinf(f6), "");
      static_assert(isinf(f9), "");
    }
  }
  
  // - a lambda-expression (5.1.2);
  struct Lambda {
    int n : []{ return 1; }(); // cxx11-error {{constant expression}} cxx11-error {{integral constant expression}} cxx11-note {{non-literal type}}
  };
  
  // - an lvalue-to-rvalue conversion (4.1) unless it is applied to
  namespace LValueToRValue {
    // - a non-volatile glvalue of integral or enumeration type that refers to a
    //   non-volatile const object with a preceding initialization, initialized
    //   with a constant expression  [Note: a string literal (2.14.5 [lex.string])
    //   corresponds to an array of such objects. -end note], or
    volatile const int vi = 1; // expected-note 2{{here}}
    const int ci = 1;
    volatile const int &vrci = ci;
    static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
    static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
  
    // - a non-volatile glvalue of literal type that refers to a non-volatile
    //   object defined with constexpr, or that refers to a sub-object of such an
    //   object, or
    struct V {
      constexpr V() : v(1) {}
      volatile int v; // expected-note {{not literal because}}
    };
    constexpr V v; // expected-error {{non-literal type}}
    struct S {
      constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
      constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {}
      int i;
      volatile int &v;
    };
    constexpr S s; // ok
    constexpr volatile S vs; // expected-note {{here}}
    constexpr const volatile S &vrs = s; // ok
    static_assert(s.i, "");
    static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
    static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
    static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
  
    // - a non-volatile glvalue of literal type that refers to a non-volatile
    //   temporary object whose lifetime has not ended, initialized with a
    //   constant expression;
    constexpr volatile S f() { return S(); }
    static_assert(f().i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
  }
  
  // DR1312: The proposed wording for this defect has issues, so we ignore this
  // bullet and instead prohibit casts from pointers to cv void (see core-20842
  // and core-20845).
  //
  // - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
  // glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
  // are neither the same type nor similar types (4.4 [conv.qual]);
  
  // - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
  // refers to a non-active member of a union or a subobject thereof;
  namespace LValueToRValueUnion {
    // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
    // of this.
    union U { int a, b; } constexpr u = U();
    static_assert(u.a == 0, "");
    constexpr const int *bp = &u.b;
    constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
  
    extern const U pu;
    constexpr const int *pua = &pu.a;
    constexpr const int *pub = &pu.b;
    constexpr U pu = { .b = 1 }; // cxx11-warning {{C++20 extension}}
    constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
    constexpr const int b2 = *pub; // ok
  }
  
  // - an id-expression that refers to a variable or data member of reference type
  //   unless the reference has a preceding initialization, initialized with a
  //   constant expression;
  namespace References {
    const int a = 2;
    int &b = *const_cast<int*>(&a);
    int c = 10; // expected-note 2 {{here}}
    int &d = c;
    constexpr int e = 42;
    int &f = const_cast<int&>(e);
    extern int &g; // expected-note {{here}}
    constexpr int &h(); // expected-note {{here}}
    int &i = h(); // expected-note {{here}}
    constexpr int &j() { return b; }
    int &k = j();
  
    struct S {
      int A : a;
      int B : b;
      int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
      int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
      int D2 : &d - &c + 1;
      int E : e / 2;
      int F : f - 11;
      int G : g; // expected-error {{constant expression}} expected-note {{initializer of 'g' is unknown}}
      int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
      int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
      int J : j();
      int K : k;
    };
  }
  
  // - a dynamic_cast (5.2.7);
  namespace DynamicCast {
    struct S { int n; };
    constexpr S s { 16 };
    struct T {
      int n : dynamic_cast<const S*>(&s)->n; // cxx11-warning {{constant expression}} cxx11-note {{dynamic_cast}}
    };
  }
  
  // - a reinterpret_cast (5.2.10);
  namespace ReinterpretCast {
    struct S { int n; };
    constexpr S s { 16 };
    struct T {
      int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
    };
    struct U {
      int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
    };
  }
  
  // - a pseudo-destructor call (5.2.4);
  namespace PseudoDtor {
    int k;
    typedef int I;
    struct T {
      int n : (k.~I(), 1); // expected-error {{constant expression}} expected-note {{visible outside that expression}}
    };
  
    constexpr int f(int a = 1) { // cxx11-error {{constant expression}} expected-note {{destroying object 'a' whose lifetime has already ended}}
      return (
          a.~I(), // cxx11-note {{pseudo-destructor}}
          0);
    }
    static_assert(f() == 0, ""); // expected-error {{constant expression}}
  
    // This is OK in C++20: the union has no active member after the
    // pseudo-destructor call, so the union destructor has no effect.
    union U { int x; };
    constexpr int g(U u = {1}) { // cxx11-error {{constant expression}}
      return (
          u.x.~I(), // cxx11-note 2{{pseudo-destructor}}
          0);
    }
    static_assert(g() == 0, ""); // cxx11-error {{constant expression}} cxx11-note {{in call}}
  }
  
  // - increment or decrement operations (5.2.6, 5.3.2);
  namespace IncDec {
    int k = 2;
    struct T {
      int n : ++k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
      int m : --k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
    };
  }
  
  // - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
  namespace std {
    struct type_info {
      virtual ~type_info();
      const char *name;
    };
  }
  namespace TypeId {
    struct S { virtual void f(); };
    constexpr S *p = 0;
    constexpr const std::type_info &ti1 = typeid(*p); // expected-error {{must be initialized by a constant expression}} cxx11-note {{typeid applied to expression of polymorphic type 'TypeId::S'}} cxx20-note {{dereferenced null pointer}}
  
    struct T {} t;
    constexpr const std::type_info &ti2 = typeid(t);
  }
  
  // - a new-expression (5.3.4);
  // - a delete-expression (5.3.5);
  namespace NewDelete {
    constexpr int *p = 0;
    struct T {
      int n : *new int(4); // expected-warning {{constant expression}} cxx11-note {{until C++20}} cxx20-note {{was not deallocated}}
      int m : (delete p, 2); // cxx11-warning {{constant expression}} cxx11-note {{until C++20}}
    };
  }
  
  // - a relational (5.9) or equality (5.10) operator where the result is
  //   unspecified;
  namespace UnspecifiedRelations {
    int a, b;
    constexpr int *p = &a, *q = &b;
    // C++11 [expr.rel]p2: If two pointers p and q of the same type point to
    // different objects that are not members of the same array or to different
    // functions, or if only one of them is null, the results of p<q, p>q, p<=q,
    // and p>=q are unspecified.
    constexpr bool u1 = p < q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u2 = p > q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u3 = p <= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u4 = p >= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u5 = p < (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u6 = p <= (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u7 = p > (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u8 = p >= (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u9 = (int*)0 < q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u10 = (int*)0 <= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u11 = (int*)0 > q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u12 = (int*)0 >= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    void f(), g();
  
    constexpr void (*pf)() = &f, (*pg)() = &g;
    constexpr bool u13 = pf < pg; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool u14 = pf == pg;
  
    // If two pointers point to non-static data members of the same object with
    // different access control, the result is unspecified.
    struct A {
    public:
      constexpr A() : a(0), b(0) {}
      int a;
      constexpr bool cmp() const { return &a < &b; } // expected-note {{comparison of address of fields 'a' and 'b' of 'A' with differing access specifiers (public vs private) has unspecified value}}
    private:
      int b;
    };
    static_assert(A().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
    class B {
    public:
      A a;
      constexpr bool cmp() const { return &a.a < &b.a; } // expected-note {{comparison of address of fields 'a' and 'b' of 'B' with differing access specifiers (public vs protected) has unspecified value}}
    protected:
      A b;
    };
    static_assert(B().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
  
    // If two pointers point to different base sub-objects of the same object, or
    // one points to a base subobject and the other points to a member, the result
    // of the comparison is unspecified. This is not explicitly called out by
    // [expr.rel]p2, but is covered by 'Other pointer comparisons are
    // unspecified'.
    struct C {
      int c[2];
    };
    struct D {
      int d;
    };
    struct E : C, D {
      struct Inner {
        int f;
      } e;
    } e;
    constexpr bool base1 = &e.c[0] < &e.d; // expected-error {{constant expression}} expected-note {{comparison of addresses of subobjects of different base classes has unspecified value}}
    constexpr bool base2 = &e.c[1] < &e.e.f; // expected-error {{constant expression}} expected-note {{comparison of address of base class subobject 'C' of class 'E' to field 'e' has unspecified value}}
    constexpr bool base3 = &e.e.f < &e.d; // expected-error {{constant expression}} expected-note {{comparison of address of base class subobject 'D' of class 'E' to field 'e' has unspecified value}}
  
    // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
    // represent the same address or are both the null pointer [...]; otherwise
    // the result is unspecified.
    struct S { int a, b; } s;
    constexpr void *null = 0;
    constexpr void *pv = (void*)&s.a;
    constexpr void *qv = (void*)&s.b;
    constexpr bool v1 = null < (int*)0;
    constexpr bool v2 = null < pv; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool v3 = null == pv; // ok
    constexpr bool v4 = qv == pv; // ok
    constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
    constexpr bool v6 = qv > null; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
    constexpr bool v7 = qv <= (void*)&s.b; // ok
    constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
  }
  
  // - an assignment or a compound assignment (5.17); or
  namespace Assignment {
    int k;
    struct T {
      int n : (k = 9); // expected-error {{constant expression}} cxx20-note {{visible outside}}
      int m : (k *= 2); // expected-error {{constant expression}} cxx20-note {{visible outside}}
    };
  
    struct Literal {
      constexpr Literal(const char *name) : name(name) {}
      const char *name;
    };
    struct Expr {
      constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
      bool IsLiteral;
      union {
        Literal l;
        // ...
      };
    };
    struct MulEq {
      constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
      Expr LHS;
      Expr RHS;
    };
    constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
    Literal a("a");
    Literal b("b");
    MulEq c = a *= b; // ok
  }
  
  // - a throw-expression (15.1)
  namespace Throw {
    struct S {
      int n : (throw "hello", 10); // expected-error {{constant expression}}
    };
  }
  
  // PR9999
  template<unsigned int v>
  class bitWidthHolding {
  public:
    static const
    unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
  };
  
  static const int width=bitWidthHolding<255>::width;
  
  template<bool b>
  struct always_false {
    static const bool value = false;
  };
  
  template<bool b>
  struct and_or {
    static const bool and_value = b && and_or<always_false<b>::value>::and_value;
    static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
  };
  
  static const bool and_value = and_or<true>::and_value;
  static const bool or_value = and_or<true>::or_value;
  
  static_assert(and_value == false, "");
  static_assert(or_value == true, "");
  
  namespace rdar13090123 {
    typedef __INTPTR_TYPE__ intptr_t;
  
    constexpr intptr_t f(intptr_t x) {
      return (((x) >> 21) * 8);
    }
  
    extern "C" int foo;
  
    constexpr intptr_t i = f((intptr_t)&foo - 10); // expected-error{{constexpr variable 'i' must be initialized by a constant expression}} \
    // expected-note{{reinterpret_cast}}
  }
  