clang/test/CXX/expr/expr.const/p2-0x.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify=expected,cxx11 -fcxx-exceptions %s -fconstexpr-depth=128 -triple i686-pc-linux-gnu
   2 // RUN: %clang_cc1 -fsyntax-only -std=c++2a -pedantic -verify=expected,cxx20 -fcxx-exceptions %s -fconstexpr-depth=128 -triple i686-pc-linux-gnu
   3
   4 // A conditional-expression is a core constant expression unless it involves one
   5 // of the following as a potentially evaluated subexpression [...]:
   6
   7 // - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant
   8 //   expression, function invocation substitution (7.1.5 [dcl.constexpr])
   9 //   replaces each occurrence of this in a constexpr member function with a
  10 //   pointer to the class object. -end note];
  11 struct This {
  12   int this1 : this1; // expected-error {{undeclared}}
  13   int this2 : this->this1; // expected-error {{invalid}}
  14   void this3() {
  15     int n1[this->this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
  16     int n2[this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
  17     (void)n1, (void)n2;
  18   }
  19 };
  20
  21 // - an invocation of a function other than a constexpr constructor for a
  22 //   literal class or a constexpr function [ Note: Overload resolution (13.3)
  23 //   is applied as usual - end note ];
  24 struct NonConstexpr1 {
  25   static int f() { return 1; } // expected-note {{here}}
  26   int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
  27 };
  28 struct NonConstexpr2 {
  29   constexpr NonConstexpr2(); // expected-note {{here}}
  30   int n;
  31 };
  32 struct NonConstexpr3 {
  33   NonConstexpr3();
  34   int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
  35 };
  36 struct NonConstexpr4 {
  37   NonConstexpr4();
  38   int n;
  39 };
  40 struct NonConstexpr5 {
  41   int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-literal type 'NonConstexpr4' cannot be used in a constant expression}}
  42 };
  43
  44 // - an invocation of an undefined constexpr function or an undefined
  45 //   constexpr constructor;
  46 struct UndefinedConstexpr {
  47   constexpr UndefinedConstexpr();
  48   static constexpr int undefinedConstexpr1(); // expected-note {{here}}
  49   int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}}
  50 };
  51
  52 // - an invocation of a constexpr function with arguments that, when substituted
  53 //   by function invocation substitution (7.1.5), do not produce a core constant
  54 //   expression;
  55 namespace NonConstExprReturn {
  56   static constexpr const int &id_ref(const int &n) {
  57     return n;
  58   }
  59   struct NonConstExprFunction {
  60     int n : id_ref(16); // ok
  61   };
  62   constexpr const int *address_of(const int &a) {
  63     return &a;
  64   }
  65   constexpr const int *return_param(int n) {
  66     return address_of(n);
  67   }
  68   struct S {
  69     int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of object outside its lifetime}}
  70   };
  71 }
  72
  73 // - an invocation of a constexpr constructor with arguments that, when
  74 //   substituted by function invocation substitution (7.1.5), do not produce all
  75 //   constant expressions for the constructor calls and full-expressions in the
  76 //   mem-initializers (including conversions);
  77 namespace NonConstExprCtor {
  78   struct T {
  79     constexpr T(const int &r) :
  80       r(r) {
  81     }
  82     const int &r;
  83   };
  84   constexpr int n = 0;
  85   constexpr T t1(n); // ok
  86   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}}
  87
  88   struct S {
  89     int n : T(4).r; // ok
  90   };
  91 }
  92
  93 // - an invocation of a constexpr function or a constexpr constructor that would
  94 //   exceed the implementation-defined recursion limits (see Annex B);
  95 namespace RecursionLimits {
  96   constexpr int RecurseForever(int n) {
  97     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}}
  98   }
  99   struct AlsoRecurseForever {
 100     constexpr AlsoRecurseForever(int n) :
 101       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}}
 102     {}
 103     int n;
 104   };
 105   struct S {
 106     int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
 107     int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
 108   };
 109 }
 110
 111 // DR1458: taking the address of an object of incomplete class type
 112 namespace IncompleteClassTypeAddr {
 113   struct S;
 114   extern S s;
 115   constexpr S *p = &s; // ok
 116   static_assert(p, "");
 117
 118   extern S sArr[];
 119   constexpr S (*p2)[] = &sArr; // ok
 120
 121   struct S {
 122     constexpr S *operator&() const { return nullptr; }
 123   };
 124   constexpr S *q = &s; // ok
 125   static_assert(!q, "");
 126 }
 127
 128 // - an operation that would have undefined behavior [Note: including, for
 129 //   example, signed integer overflow (Clause 5 [expr]), certain pointer
 130 //   arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
 131 //   shift operations (5.8 [expr.shift]) -end note];
 132 namespace UndefinedBehavior {
 133   void f(int n) {
 134     switch (n) {
 135     case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
 136     case (int)0x80000000u: // ok
 137     case (int)10000000000ll: // expected-note {{here}}
 138     case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
 139     case (int)(unsigned)(long long)4.4e9: // ok
 140     case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
 141     case (int)((float)1e37 / 1e30): // ok
 142     case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
 143       break;
 144     }
 145   }
 146
 147   constexpr int int_min = ~0x7fffffff;
 148   constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
 149   constexpr int minus_int_min_from_shift = -(1<<31); // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
 150   constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}}
 151   constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}}
 152   constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
 153   constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
 154
 155   constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
 156   constexpr int shl_0 = 0 << 0; // ok
 157   constexpr int shl_31 = 0 << 31; // ok
 158   constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}}
 159   constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
 160   constexpr int shl_unsigned_into_sign = 1u << 31; // ok
 161   constexpr int shl_unsigned_overflow = 1024u << 31; // ok
 162   constexpr int shl_signed_negative = (-3) << 1; // cxx11-error {{constant expression}} cxx11-note {{left shift of negative value -3}}
 163   constexpr int shl_signed_ok = 1 << 30; // ok
 164   constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
 165   constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
 166   constexpr int shl_signed_off_end = 2 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}}
 167   constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}}
 168   constexpr int shl_signed_overflow = 1024 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{requires 43 bits to represent}}
 169   constexpr int shl_signed_ok2 = 1024 << 20; // ok
 170
 171   constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
 172   constexpr int shr_0 = 0 >> 0; // ok
 173   constexpr int shr_31 = 0 >> 31; // ok
 174   constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}}
 175
 176   struct S {
 177     int m;
 178   };
 179   constexpr S s = { 5 };
 180   constexpr const int *p = &s.m + 1;
 181   constexpr const int &f(const int *q) {
 182     return q[0];
 183   }
 184   constexpr int n = (f(p), 0); // ok
 185   struct T {
 186     int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
 187   };
 188
 189   namespace Ptr {
 190     struct A {};
 191     struct B : A { int n; };
 192     B a[3][3];
 193     constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
 194     B b = {};
 195     constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
 196     constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
 197     constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
 198     constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
 199
 200     constexpr A *na = nullptr;
 201     constexpr B *nb = nullptr;
 202     constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
 203     constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
 204     static_assert((A*)nb == 0, "");
 205     static_assert((B*)na == 0, "");
 206     constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
 207     constexpr const int *np1 = (int*)nullptr + 0; // ok
 208     constexpr const int *np2 = &(*(int(*)[4])nullptr)[0]; // ok
 209     constexpr const int *np3 = &(*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot perform pointer arithmetic on null pointer}}
 210
 211     struct C {
 212       constexpr int f() const { return 0; }
 213     } constexpr c = C();
 214     constexpr int k1 = c.f(); // ok
 215     constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced null pointer}}
 216     constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced one-past-the-end pointer}}
 217     C c2;
 218     constexpr int k4 = c2.f(); // ok!
 219
 220     constexpr int diff1 = &a[2] - &a[0];
 221     constexpr int diff2 = &a[1][3] - &a[1][0];
 222     constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
 223     static_assert(&a[2][0] == &a[1][3], "");
 224     constexpr int diff4 = (&b + 1) - &b;
 225     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}}
 226     constexpr int diff6 = &a[1][2].n - &a[1][2].n;
 227     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}}
 228   }
 229
 230   namespace Overflow {
 231     // Signed int overflow.
 232     constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
 233     constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
 234     constexpr int n3 = n1 + 1; // ok
 235     constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
 236     constexpr int n5 = -65536 * 32768; // ok
 237     constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
 238     constexpr int n7 = -n3 + -1; // ok
 239     constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
 240     constexpr int n9 = n3 - 0; // ok
 241     constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
 242     constexpr int n11 = -1 - n3; // ok
 243     constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
 244     constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
 245     constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
 246     constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
 247     constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
 248     constexpr signed char c2 = '\x64' * '\2'; // also ok  expected-warning{{changes value}}
 249     constexpr long long ll1 = 0x7fffffffffffffff; // ok
 250     constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
 251     constexpr long long ll3 = -ll1 - 1; // ok
 252     constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
 253     constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
 254
 255     // Yikes.
 256     char melchizedek[2200000000];
 257     typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
 258     constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
 259     constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
 260     constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
 261     constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
 262
 263     // Unsigned int overflow.
 264     static_assert(65536u * 65536u == 0u, ""); // ok
 265     static_assert(4294967295u + 1u == 0u, ""); // ok
 266     static_assert(0u - 1u == 4294967295u, ""); // ok
 267     static_assert(~0u * ~0u == 1u, ""); // ok
 268
 269     template<typename T> constexpr bool isinf(T v) { return v && v / 2 == v; }
 270
 271     // Floating-point overflow and NaN.
 272     constexpr float f1 = 1e38f * 3.4028f; // ok
 273     constexpr float f2 = 1e38f * 3.4029f; // ok, +inf is in range of representable values
 274     constexpr float f3 = 1e38f / -.2939f; // ok
 275     constexpr float f4 = 1e38f / -.2938f; // ok, -inf is in range of representable values
 276     constexpr float f5 = 2e38f + 2e38f; // ok, +inf is in range of representable values
 277     constexpr float f6 = -2e38f - 2e38f; // ok, -inf is in range of representable values
 278     constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
 279     constexpr float f8 = 1.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
 280     constexpr float f9 = 1e308 / 1e-308; // ok, +inf
 281     constexpr float f10 = f2 - f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
 282     constexpr float f11 = f2 + f4; // expected-error {{constant expression}} expected-note {{produces a NaN}}
 283     constexpr float f12 = f2 / f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
 284 #pragma float_control(push)
 285 #pragma float_control(except, on)
 286 constexpr float pi = 3.14f;
 287 constexpr unsigned ubig = 0xFFFFFFFF;
 288 constexpr float ce = 1.0 / 3.0; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
 289 constexpr int ci = (int) pi;
 290 constexpr float fbig = (float) ubig; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
 291 constexpr float fabspi = __builtin_fabs(pi); // no error expected
 292 constexpr float negpi = -pi; // expect no error on unary operator
 293 #pragma float_control(pop)
 294     static_assert(!isinf(f1), "");
 295     static_assert(isinf(f2), "");
 296     static_assert(!isinf(f3), "");
 297     static_assert(isinf(f4), "");
 298     static_assert(isinf(f5), "");
 299     static_assert(isinf(f6), "");
 300     static_assert(isinf(f9), "");
 301   }
 302
 303 #if __cplusplus >= 201703L
 304 namespace CompoundAssignment {
 305 constexpr int rem() { // expected-error {{constexpr function never produces a constant expression}}
 306     int x = ~__INT_MAX__;
 307     return x%=-1; // cxx20-note {{value 2147483648 is outside the range of representable values of type 'int'}}
 308 }
 309 }
 310 #endif
 311 }
 312
 313 // - a lambda-expression (5.1.2);
 314 struct Lambda {
 315   int n : []{ return 1; }(); // cxx11-error {{constant expression}} cxx11-error {{integral constant expression}} cxx11-note {{non-literal type}}
 316 };
 317
 318 // - an lvalue-to-rvalue conversion (4.1) unless it is applied to
 319 namespace LValueToRValue {
 320   // - a non-volatile glvalue of integral or enumeration type that refers to a
 321   //   non-volatile const object with a preceding initialization, initialized
 322   //   with a constant expression  [Note: a string literal (2.14.5 [lex.string])
 323   //   corresponds to an array of such objects. -end note], or
 324   volatile const int vi = 1; // expected-note 2{{here}}
 325   const int ci = 1;
 326   volatile const int &vrci = ci;
 327   static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 328   static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
 329   static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 330
 331   // - a non-volatile glvalue of literal type that refers to a non-volatile
 332   //   object defined with constexpr, or that refers to a sub-object of such an
 333   //   object, or
 334   struct V {
 335     constexpr V() : v(1) {}
 336     volatile int v; // expected-note {{not literal because}}
 337   };
 338   constexpr V v; // expected-error {{non-literal type}}
 339   struct S {
 340     constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
 341     constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {}
 342     int i;
 343     volatile int &v;
 344   };
 345   constexpr S s; // ok
 346   constexpr volatile S vs; // expected-note {{here}}
 347   constexpr const volatile S &vrs = s; // ok
 348   static_assert(s.i, "");
 349   static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 350   static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
 351   static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 352   static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
 353   static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 354
 355   // - a non-volatile glvalue of literal type that refers to a non-volatile
 356   //   temporary object whose lifetime has not ended, initialized with a
 357   //   constant expression;
 358   constexpr volatile S f() { return S(); }
 359   static_assert(f().i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 360   static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 361 }
 362
 363 // DR1312: The proposed wording for this defect has issues, so we ignore this
 364 // bullet and instead prohibit casts from pointers to cv void (see core-20842
 365 // and core-20845).
 366 //
 367 // - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
 368 // glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
 369 // are neither the same type nor similar types (4.4 [conv.qual]);
 370
 371 // - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
 372 // refers to a non-active member of a union or a subobject thereof;
 373 namespace LValueToRValueUnion {
 374   // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
 375   // of this.
 376   union U { int a, b; } constexpr u = U();
 377   static_assert(u.a == 0, "");
 378   constexpr const int *bp = &u.b;
 379   constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
 380
 381   extern const U pu;
 382   constexpr const int *pua = &pu.a;
 383   constexpr const int *pub = &pu.b;
 384   constexpr U pu = { .b = 1 }; // cxx11-warning {{C++20 extension}}
 385   constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
 386   constexpr const int b2 = *pub; // ok
 387 }
 388
 389 // - an id-expression that refers to a variable or data member of reference type
 390 //   unless the reference has a preceding initialization, initialized with a
 391 //   constant expression;
 392 namespace References {
 393   const int a = 2;
 394   int &b = *const_cast<int*>(&a);
 395   int c = 10; // expected-note 2 {{here}}
 396   int &d = c;
 397   constexpr int e = 42;
 398   int &f = const_cast<int&>(e);
 399   extern int &g; // expected-note {{here}}
 400   constexpr int &h(); // expected-note {{here}}
 401   int &i = h(); // expected-note {{here}}
 402   constexpr int &j() { return b; }
 403   int &k = j();
 404
 405   struct S {
 406     int A : a;
 407     int B : b;
 408     int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
 409     int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
 410     int D2 : &d - &c + 1;
 411     int E : e / 2;
 412     int F : f - 11;
 413     int G : g; // expected-error {{constant expression}} expected-note {{initializer of 'g' is unknown}}
 414     int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
 415     int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
 416     int J : j();
 417     int K : k;
 418   };
 419 }
 420
 421 // - a dynamic_cast (5.2.7);
 422 namespace DynamicCast {
 423   struct S { int n; };
 424   constexpr S s { 16 };
 425   struct T {
 426     int n : dynamic_cast<const S*>(&s)->n; // cxx11-warning {{constant expression}} cxx11-note {{dynamic_cast}}
 427   };
 428 }
 429
 430 // - a reinterpret_cast (5.2.10);
 431 namespace ReinterpretCast {
 432   struct S { int n; };
 433   constexpr S s { 16 };
 434   struct T {
 435     int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
 436   };
 437   struct U {
 438     int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
 439   };
 440 }
 441
 442 // - a pseudo-destructor call (5.2.4);
 443 namespace PseudoDtor {
 444   int k;
 445   typedef int I;
 446   struct T {
 447     int n : (k.~I(), 1); // expected-error {{constant expression}} expected-note {{visible outside that expression}}
 448   };
 449
 450   constexpr int f(int a = 1) { // cxx11-error {{constant expression}} expected-note {{destroying object 'a' whose lifetime has already ended}}
 451     return (
 452         a.~I(), // cxx11-note {{pseudo-destructor}}
 453         0);
 454   }
 455   static_assert(f() == 0, ""); // expected-error {{constant expression}}
 456
 457   // This is OK in C++20: the union has no active member after the
 458   // pseudo-destructor call, so the union destructor has no effect.
 459   union U { int x; };
 460   constexpr int g(U u = {1}) { // cxx11-error {{constant expression}}
 461     return (
 462         u.x.~I(), // cxx11-note 2{{pseudo-destructor}}
 463         0);
 464   }
 465   static_assert(g() == 0, ""); // cxx11-error {{constant expression}} cxx11-note {{in call}}
 466 }
 467
 468 // - increment or decrement operations (5.2.6, 5.3.2);
 469 namespace IncDec {
 470   int k = 2;
 471   struct T {
 472     int n : ++k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
 473     int m : --k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
 474   };
 475 }
 476
 477 // - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
 478 namespace std {
 479   struct type_info {
 480     virtual ~type_info();
 481     const char *name;
 482   };
 483 }
 484 namespace TypeId {
 485   struct S { virtual void f(); };
 486   constexpr S *p = 0;
 487   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 'S'}} cxx20-note {{dereferenced null pointer}}
 488
 489   struct T {} t;
 490   constexpr const std::type_info &ti2 = typeid(t);
 491 }
 492
 493 // - a new-expression (5.3.4);
 494 // - a delete-expression (5.3.5);
 495 namespace NewDelete {
 496   constexpr int *p = 0;
 497   struct T {
 498     int n : *new int(4); // expected-warning {{constant expression}} cxx11-note {{until C++20}} cxx20-note {{was not deallocated}}
 499     int m : (delete p, 2); // cxx11-warning {{constant expression}} cxx11-note {{until C++20}}
 500   };
 501 }
 502
 503 // - a relational (5.9) or equality (5.10) operator where the result is
 504 //   unspecified;
 505 namespace UnspecifiedRelations {
 506   int a, b;
 507   constexpr int *p = &a, *q = &b;
 508   // C++11 [expr.rel]p2: If two pointers p and q of the same type point to
 509   // different objects that are not members of the same array or to different
 510   // functions, or if only one of them is null, the results of p<q, p>q, p<=q,
 511   // and p>=q are unspecified.
 512   constexpr bool u1 = p < q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
 513   constexpr bool u2 = p > q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
 514   constexpr bool u3 = p <= q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
 515   constexpr bool u4 = p >= q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
 516   constexpr bool u5 = p < (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
 517   constexpr bool u6 = p <= (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
 518   constexpr bool u7 = p > (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
 519   constexpr bool u8 = p >= (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
 520   constexpr bool u9 = (int*)0 < q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
 521   constexpr bool u10 = (int*)0 <= q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
 522   constexpr bool u11 = (int*)0 > q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
 523   constexpr bool u12 = (int*)0 >= q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
 524   void f(), g();
 525
 526   constexpr void (*pf)() = &f, (*pg)() = &g;
 527   constexpr bool u13 = pf < pg; // expected-error {{constant expression}} expected-note {{comparison between '&f' and '&g' has unspecified value}}
 528                                 // expected-warning@-1 {{ordered comparison of function pointers}}
 529   constexpr bool u14 = pf == pg;
 530
 531   // If two pointers point to non-static data members of the same object with
 532   // different access control, the result is unspecified.
 533   struct A {
 534   public:
 535     constexpr A() : a(0), b(0) {}
 536     int a;
 537     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}}
 538   private:
 539     int b;
 540   };
 541   static_assert(A().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
 542   class B {
 543   public:
 544     A a;
 545     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}}
 546   protected:
 547     A b;
 548   };
 549   static_assert(B().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
 550
 551   // If two pointers point to different base sub-objects of the same object, or
 552   // one points to a base subobject and the other points to a member, the result
 553   // of the comparison is unspecified. This is not explicitly called out by
 554   // [expr.rel]p2, but is covered by 'Other pointer comparisons are
 555   // unspecified'.
 556   struct C {
 557     int c[2];
 558   };
 559   struct D {
 560     int d;
 561   };
 562   struct E : C, D {
 563     struct Inner {
 564       int f;
 565     } e;
 566   } e;
 567   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}}
 568   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}}
 569   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}}
 570
 571   // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
 572   // represent the same address or are both the null pointer [...]; otherwise
 573   // the result is unspecified.
 574   // Same address restriction removed by CWG2749
 575   struct S { int a, b; } s;
 576   constexpr void *null = 0;
 577   constexpr void *pv = (void*)&s.a;
 578   constexpr void *qv = (void*)&s.b;
 579   constexpr bool v1 = null < (int*)0;
 580   constexpr bool v2 = null < pv; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&s.a' has unspecified value}}
 581   constexpr bool v3 = null == pv;
 582   constexpr bool v4 = qv == pv;
 583   constexpr bool v5 = qv >= pv;
 584   constexpr bool v6 = qv > null; // expected-error {{constant expression}} expected-note {{comparison between '&s.b' and 'nullptr' has unspecified value}}
 585   constexpr bool v7 = qv <= (void*)&s.b;
 586   constexpr bool v8 = qv > (void*)&s.a;
 587 }
 588
 589 // - an assignment or a compound assignment (5.17); or
 590 namespace Assignment {
 591   int k;
 592   struct T {
 593     int n : (k = 9); // expected-error {{constant expression}} cxx20-note {{visible outside}}
 594     int m : (k *= 2); // expected-error {{constant expression}} cxx20-note {{visible outside}}
 595   };
 596
 597   struct Literal {
 598     constexpr Literal(const char *name) : name(name) {}
 599     const char *name;
 600   };
 601   struct Expr {
 602     constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
 603     bool IsLiteral;
 604     union {
 605       Literal l;
 606       // ...
 607     };
 608   };
 609   struct MulEq {
 610     constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
 611     Expr LHS;
 612     Expr RHS;
 613   };
 614   constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
 615   Literal a("a");
 616   Literal b("b");
 617   MulEq c = a *= b; // ok
 618 }
 619
 620 // - a throw-expression (15.1)
 621 namespace Throw {
 622   struct S {
 623     int n : (throw "hello", 10); // expected-error {{constant expression}}
 624   };
 625 }
 626
 627 // PR9999
 628 template<unsigned int v>
 629 class bitWidthHolding {
 630 public:
 631   static const
 632   unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
 633 };
 634
 635 static const int width=bitWidthHolding<255>::width;
 636
 637 template<bool b>
 638 struct always_false {
 639   static const bool value = false;
 640 };
 641
 642 template<bool b>
 643 struct and_or {
 644   static const bool and_value = b && and_or<always_false<b>::value>::and_value;
 645   static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
 646 };
 647
 648 static const bool and_value = and_or<true>::and_value;
 649 static const bool or_value = and_or<true>::or_value;
 650
 651 static_assert(and_value == false, "");
 652 static_assert(or_value == true, "");
 653
 654 namespace rdar13090123 {
 655   typedef __INTPTR_TYPE__ intptr_t;
 656
 657   constexpr intptr_t f(intptr_t x) {
 658     return (((x) >> 21) * 8);
 659   }
 660
 661   extern "C" int foo;
 662
 663   constexpr intptr_t i = f((intptr_t)&foo - 10); // expected-error{{constexpr variable 'i' must be initialized by a constant expression}} \
 664   // expected-note{{reinterpret_cast}}
 665 }