Home | History | Annotate | Download | only in expr.const 
      1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu
      2 
      3 // A conditional-expression is a core constant expression unless it involves one
      4 // of the following as a potentially evaluated subexpression [...]:
      5 
      6 // - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant
      7 //   expression, function invocation substitution (7.1.5 [dcl.constexpr])
      8 //   replaces each occurrence of this in a constexpr member function with a
      9 //   pointer to the class object. -end note];
     10 struct This {
     11   int this1 : this1; // expected-error {{undeclared}}
     12   int this2 : this->this1; // expected-error {{invalid}}
     13   void this3() {
     14     int n1[this->this1]; // expected-warning {{variable length array}}
     15     int n2[this1]; // expected-warning {{variable length array}}
     16     (void)n1, (void)n2;
     17   }
     18 };
     19 
     20 // - an invocation of a function other than a constexpr constructor for a
     21 //   literal class or a constexpr function [ Note: Overload resolution (13.3)
     22 //   is applied as usual - end note ];
     23 struct NonConstexpr1 {
     24   static int f() { return 1; } // expected-note {{here}}
     25   int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
     26 };
     27 struct NonConstexpr2 {
     28   constexpr NonConstexpr2(); // expected-note {{here}}
     29   int n;
     30 };
     31 struct NonConstexpr3 {
     32   NonConstexpr3();
     33   int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
     34 };
     35 struct NonConstexpr4 {
     36   NonConstexpr4(); // expected-note {{declared here}}
     37   int n;
     38 };
     39 struct NonConstexpr5 {
     40   int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-constexpr constructor 'NonConstexpr4' cannot be used in a constant expression}}
     41 };
     42 
     43 // - an invocation of an undefined constexpr function or an undefined
     44 //   constexpr constructor;
     45 struct UndefinedConstexpr {
     46   constexpr UndefinedConstexpr();
     47   static constexpr int undefinedConstexpr1(); // expected-note {{here}}
     48   int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}}
     49 };
     50 
     51 // - an invocation of a constexpr function with arguments that, when substituted
     52 //   by function invocation substitution (7.1.5), do not produce a core constant
     53 //   expression;
     54 namespace NonConstExprReturn {
     55   static constexpr const int &id_ref(const int &n) {
     56     return n;
     57   }
     58   struct NonConstExprFunction {
     59     int n : id_ref(16); // ok
     60   };
     61   constexpr const int *address_of(const int &a) {
     62     return &a;
     63   }
     64   constexpr const int *return_param(int n) { // expected-note {{declared here}}
     65     return address_of(n);
     66   }
     67   struct S {
     68     int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of variable whose lifetime has ended}}
     69   };
     70 }
     71 
     72 // - an invocation of a constexpr constructor with arguments that, when
     73 //   substituted by function invocation substitution (7.1.5), do not produce all
     74 //   constant expressions for the constructor calls and full-expressions in the
     75 //   mem-initializers (including conversions);
     76 namespace NonConstExprCtor {
     77   struct T {
     78     constexpr T(const int &r) :
     79       r(r) {
     80     }
     81     const int &r;
     82   };
     83   constexpr int n = 0;
     84   constexpr T t1(n); // ok
     85   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}}
     86 
     87   struct S {
     88     int n : T(4).r; // ok
     89   };
     90 }
     91 
     92 // - an invocation of a constexpr function or a constexpr constructor that would
     93 //   exceed the implementation-defined recursion limits (see Annex B);
     94 namespace RecursionLimits {
     95   constexpr int RecurseForever(int n) {
     96     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}}
     97   }
     98   struct AlsoRecurseForever {
     99     constexpr AlsoRecurseForever(int n) :
    100       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}}
    101     {}
    102     int n;
    103   };
    104   struct S {
    105     int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
    106     int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
    107   };
    108 }
    109 
    110 // DR1458: taking the address of an object of incomplete class type
    111 namespace IncompleteClassTypeAddr {
    112   struct S;
    113   extern S s;
    114   constexpr S *p = &s; // ok
    115   static_assert(p, "");
    116 
    117   extern S sArr[];
    118   constexpr S (*p2)[] = &sArr; // ok
    119 
    120   struct S {
    121     constexpr S *operator&() const { return nullptr; }
    122   };
    123   constexpr S *q = &s; // ok
    124   static_assert(!q, "");
    125 }
    126 
    127 // - an operation that would have undefined behavior [Note: including, for
    128 //   example, signed integer overflow (Clause 5 [expr]), certain pointer
    129 //   arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
    130 //   shift operations (5.8 [expr.shift]) -end note];
    131 namespace UndefinedBehavior {
    132   void f(int n) {
    133     switch (n) {
    134     case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
    135     case (int)0x80000000u: // ok
    136     case (int)10000000000ll: // expected-note {{here}}
    137     case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
    138     case (int)(unsigned)(long long)4.4e9: // ok
    139     case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value 1.0E+300 is outside the range of representable values of type 'float'}}
    140     case (int)((float)1e37 / 1e30): // ok
    141     case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value 65536 is outside the range of representable values of type '__fp16'}}
    142       break;
    143     }
    144   }
    145 
    146   constexpr int int_min = ~0x7fffffff;
    147   constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
    148   constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}}
    149   constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}}
    150   constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
    151   constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
    152 
    153   constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}}
    154   constexpr int shl_0 = 0 << 0; // ok
    155   constexpr int shl_31 = 0 << 31; // ok
    156   constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}} expected-warning {{>= width of type}}
    157   constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
    158   constexpr int shl_unsigned_into_sign = 1u << 31; // ok
    159   constexpr int shl_unsigned_overflow = 1024u << 31; // ok
    160   constexpr int shl_signed_negative = (-3) << 1; // expected-warning {{shifting a negative signed value is undefined}} // expected-error {{constant expression}} expected-note {{left shift of negative value -3}}
    161   constexpr int shl_signed_ok = 1 << 30; // ok
    162   constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
    163   constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
    164   constexpr int shl_signed_off_end = 2 << 31; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}}
    165   constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}}
    166   constexpr int shl_signed_overflow = 1024 << 31; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{requires 43 bits to represent}}
    167   constexpr int shl_signed_ok2 = 1024 << 20; // ok
    168 
    169   constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}}
    170   constexpr int shr_0 = 0 >> 0; // ok
    171   constexpr int shr_31 = 0 >> 31; // ok
    172   constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}} expected-warning {{>= width of type}}
    173 
    174   struct S {
    175     int m;
    176   };
    177   constexpr S s = { 5 };
    178   constexpr const int *p = &s.m + 1;
    179   constexpr const int &f(const int *q) {
    180     return q[0];
    181   }
    182   constexpr int n = (f(p), 0); // ok
    183   struct T {
    184     int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
    185   };
    186 
    187   namespace Ptr {
    188     struct A {};
    189     struct B : A { int n; };
    190     B a[3][3];
    191     constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
    192     B b = {};
    193     constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
    194     constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
    195     constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
    196     constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
    197 
    198     constexpr A *na = nullptr;
    199     constexpr B *nb = nullptr;
    200     constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
    201     constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
    202     static_assert((A*)nb == 0, "");
    203     static_assert((B*)na == 0, "");
    204     constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
    205     constexpr const int *np1 = (int*)nullptr + 0; // ok
    206     constexpr const int *np2 = &(*(int(*)[4])nullptr)[0]; // ok
    207     constexpr const int *np3 = &(*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot perform pointer arithmetic on null pointer}}
    208 
    209     struct C {
    210       constexpr int f() const { return 0; }
    211     } constexpr c = C();
    212     constexpr int k1 = c.f(); // ok
    213     constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{cannot call member function on null pointer}}
    214     constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{cannot call member function on pointer past the end of object}}
    215     C c2;
    216     constexpr int k4 = c2.f(); // ok!
    217 
    218     constexpr int diff1 = &a[2] - &a[0];
    219     constexpr int diff2 = &a[1][3] - &a[1][0];
    220     constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
    221     static_assert(&a[2][0] == &a[1][3], "");
    222     constexpr int diff4 = (&b + 1) - &b;
    223     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}}
    224     constexpr int diff6 = &a[1][2].n - &a[1][2].n;
    225     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}}
    226   }
    227 
    228   namespace Overflow {
    229     // Signed int overflow.
    230     constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
    231     constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
    232     constexpr int n3 = n1 + 1; // ok
    233     constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
    234     constexpr int n5 = -65536 * 32768; // ok
    235     constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
    236     constexpr int n7 = -n3 + -1; // ok
    237     constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
    238     constexpr int n9 = n3 - 0; // ok
    239     constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
    240     constexpr int n11 = -1 - n3; // ok
    241     constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
    242     constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
    243     constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
    244     constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
    245     constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
    246     constexpr signed char c2 = '\x64' * '\2'; // also ok  expected-warning{{changes value}}
    247     constexpr long long ll1 = 0x7fffffffffffffff; // ok
    248     constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
    249     constexpr long long ll3 = -ll1 - 1; // ok
    250     constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
    251     constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
    252 
    253     // Yikes.
    254     char melchizedek[2200000000];
    255     typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
    256     constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
    257     constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
    258     constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
    259     constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
    260 
    261     // Unsigned int overflow.
    262     static_assert(65536u * 65536u == 0u, ""); // ok
    263     static_assert(4294967295u + 1u == 0u, ""); // ok
    264     static_assert(0u - 1u == 4294967295u, ""); // ok
    265     static_assert(~0u * ~0u == 1u, ""); // ok
    266 
    267     // Floating-point overflow and NaN.
    268     constexpr float f1 = 1e38f * 3.4028f; // ok
    269     constexpr float f2 = 1e38f * 3.4029f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
    270     constexpr float f3 = 1e38f / -.2939f; // ok
    271     constexpr float f4 = 1e38f / -.2938f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
    272     constexpr float f5 = 2e38f + 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
    273     constexpr float f6 = -2e38f - 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
    274     constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces a NaN}}
    275   }
    276 }
    277 
    278 // - a lambda-expression (5.1.2);
    279 struct Lambda {
    280   int n : []{ return 1; }(); // expected-error {{constant expression}} expected-error {{integral constant expression}} expected-note {{non-literal type}}
    281 };
    282 
    283 // - an lvalue-to-rvalue conversion (4.1) unless it is applied to
    284 namespace LValueToRValue {
    285   // - a non-volatile glvalue of integral or enumeration type that refers to a
    286   //   non-volatile const object with a preceding initialization, initialized
    287   //   with a constant expression  [Note: a string literal (2.14.5 [lex.string])
    288   //   corresponds to an array of such objects. -end note], or
    289   volatile const int vi = 1; // expected-note 2{{here}}
    290   const int ci = 1;
    291   volatile const int &vrci = ci;
    292   static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    293   static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
    294   static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    295 
    296   // - a non-volatile glvalue of literal type that refers to a non-volatile
    297   //   object defined with constexpr, or that refers to a sub-object of such an
    298   //   object, or
    299   struct V {
    300     constexpr V() : v(1) {}
    301     volatile int v; // expected-note {{not literal because}}
    302   };
    303   constexpr V v; // expected-error {{non-literal type}}
    304   struct S {
    305     constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
    306     constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {}
    307     int i;
    308     volatile int &v;
    309   };
    310   constexpr S s; // ok
    311   constexpr volatile S vs; // expected-note {{here}}
    312   constexpr const volatile S &vrs = s; // ok
    313   static_assert(s.i, "");
    314   static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    315   static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
    316   static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    317   static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
    318   static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    319 
    320   // - a non-volatile glvalue of literal type that refers to a non-volatile
    321   //   temporary object whose lifetime has not ended, initialized with a
    322   //   constant expression;
    323   constexpr volatile S f() { return S(); }
    324   static_assert(f().i, ""); // ok! there's no lvalue-to-rvalue conversion here!
    325   static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
    326 }
    327 
    328 // DR1312: The proposed wording for this defect has issues, so we ignore this
    329 // bullet and instead prohibit casts from pointers to cv void (see core-20842
    330 // and core-20845).
    331 //
    332 // - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
    333 // glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
    334 // are neither the same type nor similar types (4.4 [conv.qual]);
    335 
    336 // - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
    337 // refers to a non-active member of a union or a subobject thereof;
    338 namespace LValueToRValueUnion {
    339   // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
    340   // of this.
    341   union U { int a, b; } constexpr u = U();
    342   static_assert(u.a == 0, "");
    343   constexpr const int *bp = &u.b;
    344   constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
    345 
    346   extern const U pu;
    347   constexpr const int *pua = &pu.a;
    348   constexpr const int *pub = &pu.b;
    349   constexpr U pu = { .b = 1 }; // expected-warning {{C99 feature}}
    350   constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
    351   constexpr const int b2 = *pub; // ok
    352 }
    353 
    354 // - an id-expression that refers to a variable or data member of reference type
    355 //   unless the reference has a preceding initialization, initialized with a
    356 //   constant expression;
    357 namespace References {
    358   const int a = 2;
    359   int &b = *const_cast<int*>(&a);
    360   int c = 10; // expected-note 2 {{here}}
    361   int &d = c;
    362   constexpr int e = 42;
    363   int &f = const_cast<int&>(e);
    364   extern int &g;
    365   constexpr int &h(); // expected-note {{here}}
    366   int &i = h(); // expected-note {{here}}
    367   constexpr int &j() { return b; }
    368   int &k = j();
    369 
    370   struct S {
    371     int A : a;
    372     int B : b;
    373     int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
    374     int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
    375     int D2 : &d - &c + 1;
    376     int E : e / 2;
    377     int F : f - 11;
    378     int G : g; // expected-error {{constant expression}}
    379     int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
    380     int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
    381     int J : j();
    382     int K : k;
    383   };
    384 }
    385 
    386 // - a dynamic_cast (5.2.7);
    387 namespace DynamicCast {
    388   struct S { int n; };
    389   constexpr S s { 16 };
    390   struct T {
    391     int n : dynamic_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{dynamic_cast}}
    392   };
    393 }
    394 
    395 // - a reinterpret_cast (5.2.10);
    396 namespace ReinterpretCast {
    397   struct S { int n; };
    398   constexpr S s { 16 };
    399   struct T {
    400     int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
    401   };
    402   struct U {
    403     int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
    404   };
    405 }
    406 
    407 // - a pseudo-destructor call (5.2.4);
    408 namespace PseudoDtor {
    409   int k;
    410   typedef int I;
    411   struct T {
    412     int n : (k.~I(), 0); // expected-error {{constant expression}}
    413   };
    414 }
    415 
    416 // - increment or decrement operations (5.2.6, 5.3.2);
    417 namespace IncDec {
    418   int k = 2;
    419   struct T {
    420     int n : ++k; // expected-error {{constant expression}}
    421     int m : --k; // expected-error {{constant expression}}
    422   };
    423 }
    424 
    425 // - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
    426 namespace std {
    427   struct type_info {
    428     virtual ~type_info();
    429     const char *name;
    430   };
    431 }
    432 namespace TypeId {
    433   struct S { virtual void f(); };
    434   constexpr S *p = 0;
    435   constexpr const std::type_info &ti1 = typeid(*p); // expected-error {{must be initialized by a constant expression}} expected-note {{typeid applied to expression of polymorphic type 'TypeId::S'}}
    436 
    437   struct T {} t;
    438   constexpr const std::type_info &ti2 = typeid(t);
    439 }
    440 
    441 // - a new-expression (5.3.4);
    442 // - a delete-expression (5.3.5);
    443 namespace NewDelete {
    444   int *p = 0;
    445   struct T {
    446     int n : *new int(4); // expected-error {{constant expression}}
    447     int m : (delete p, 2); // expected-error {{constant expression}}
    448   };
    449 }
    450 
    451 // - a relational (5.9) or equality (5.10) operator where the result is
    452 //   unspecified;
    453 namespace UnspecifiedRelations {
    454   int a, b;
    455   constexpr int *p = &a, *q = &b;
    456   // C++11 [expr.rel]p2: If two pointers p and q of the same type point to
    457   // different objects that are not members of the same array or to different
    458   // functions, or if only one of them is null, the results of p<q, p>q, p<=q,
    459   // and p>=q are unspecified.
    460   constexpr bool u1 = p < q; // expected-error {{constant expression}}
    461   constexpr bool u2 = p > q; // expected-error {{constant expression}}
    462   constexpr bool u3 = p <= q; // expected-error {{constant expression}}
    463   constexpr bool u4 = p >= q; // expected-error {{constant expression}}
    464   constexpr bool u5 = p < 0; // expected-error {{constant expression}}
    465   constexpr bool u6 = p <= 0; // expected-error {{constant expression}}
    466   constexpr bool u7 = p > 0; // expected-error {{constant expression}}
    467   constexpr bool u8 = p >= 0; // expected-error {{constant expression}}
    468   constexpr bool u9 = 0 < q; // expected-error {{constant expression}}
    469   constexpr bool u10 = 0 <= q; // expected-error {{constant expression}}
    470   constexpr bool u11 = 0 > q; // expected-error {{constant expression}}
    471   constexpr bool u12 = 0 >= q; // expected-error {{constant expression}}
    472   void f(), g();
    473 
    474   constexpr void (*pf)() = &f, (*pg)() = &g;
    475   constexpr bool u13 = pf < pg; // expected-error {{constant expression}}
    476   constexpr bool u14 = pf == pg;
    477 
    478   // If two pointers point to non-static data members of the same object with
    479   // different access control, the result is unspecified.
    480   struct A {
    481   public:
    482     constexpr A() : a(0), b(0) {}
    483     int a;
    484     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}}
    485   private:
    486     int b;
    487   };
    488   static_assert(A().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
    489   class B {
    490   public:
    491     A a;
    492     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}}
    493   protected:
    494     A b;
    495   };
    496   static_assert(B().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
    497 
    498   // If two pointers point to different base sub-objects of the same object, or
    499   // one points to a base subobject and the other points to a member, the result
    500   // of the comparison is unspecified. This is not explicitly called out by
    501   // [expr.rel]p2, but is covered by 'Other pointer comparisons are
    502   // unspecified'.
    503   struct C {
    504     int c[2];
    505   };
    506   struct D {
    507     int d;
    508   };
    509   struct E : C, D {
    510     struct Inner {
    511       int f;
    512     } e;
    513   } e;
    514   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}}
    515   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}}
    516   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}}
    517 
    518   // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
    519   // represent the same address or are both the null pointer [...]; otherwise
    520   // the result is unspecified.
    521   struct S { int a, b; } s;
    522   constexpr void *null = 0;
    523   constexpr void *pv = (void*)&s.a;
    524   constexpr void *qv = (void*)&s.b;
    525   constexpr bool v1 = null < 0;
    526   constexpr bool v2 = null < pv; // expected-error {{constant expression}}
    527   constexpr bool v3 = null == pv; // ok
    528   constexpr bool v4 = qv == pv; // ok
    529   constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
    530   constexpr bool v6 = qv > null; // expected-error {{constant expression}}
    531   constexpr bool v7 = qv <= (void*)&s.b; // ok
    532   constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
    533 }
    534 
    535 // - an assignment or a compound assignment (5.17); or
    536 namespace Assignment {
    537   int k;
    538   struct T {
    539     int n : (k = 9); // expected-error {{constant expression}}
    540     int m : (k *= 2); // expected-error {{constant expression}}
    541   };
    542 
    543   struct Literal {
    544     constexpr Literal(const char *name) : name(name) {}
    545     const char *name;
    546   };
    547   struct Expr {
    548     constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
    549     bool IsLiteral;
    550     union {
    551       Literal l;
    552       // ...
    553     };
    554   };
    555   struct MulEq {
    556     constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
    557     Expr LHS;
    558     Expr RHS;
    559   };
    560   constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
    561   Literal a("a");
    562   Literal b("b");
    563   MulEq c = a *= b; // ok
    564 }
    565 
    566 // - a throw-expression (15.1)
    567 namespace Throw {
    568   struct S {
    569     int n : (throw "hello", 10); // expected-error {{constant expression}}
    570   };
    571 }
    572 
    573 // PR9999
    574 template<unsigned int v>
    575 class bitWidthHolding {
    576 public:
    577   static const
    578   unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
    579 };
    580 
    581 static const int width=bitWidthHolding<255>::width;
    582 
    583 template<bool b>
    584 struct always_false {
    585   static const bool value = false;
    586 };
    587 
    588 template<bool b>
    589 struct and_or {
    590   static const bool and_value = b && and_or<always_false<b>::value>::and_value;
    591   static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
    592 };
    593 
    594 static const bool and_value = and_or<true>::and_value;
    595 static const bool or_value = and_or<true>::or_value;
    596 
    597 static_assert(and_value == false, "");
    598 static_assert(or_value == true, "");
    599 
    600 namespace rdar13090123 {
    601   typedef __INTPTR_TYPE__ intptr_t;
    602 
    603   constexpr intptr_t f(intptr_t x) {
    604     return (((x) >> 21) * 8);
    605   }
    606 
    607   extern "C" int foo;
    608 
    609   constexpr intptr_t i = f((intptr_t)&foo - 10); // expected-error{{constexpr variable 'i' must be initialized by a constant expression}} \
    610   // expected-note{{reinterpret_cast}}
    611 }
    612