p2-0x.cpp revision 925d8e7c0f18e03dc4bc634b3c6c1ec09373d993 
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];
10struct 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 ];
23struct 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};
27struct NonConstexpr2 {
28  constexpr NonConstexpr2(); // expected-note {{here}}
29  int n;
30};
31struct NonConstexpr3 {
32  NonConstexpr3();
33  int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
34};
35struct NonConstexpr4 {
36  NonConstexpr4(); // expected-note {{declared here}}
37  int n;
38};
39struct 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;
45struct 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 constant
53//   expression;
54namespace NonConstExprReturn {
55  static constexpr const int &id_ref(const int &n) {
56    return n; // expected-note {{reference to temporary cannot be returned from a constexpr function}}
57  }
58  struct NonConstExprFunction {
59    int n : id_ref( // expected-error {{constant expression}} expected-note {{in call to 'id_ref(16)'}}
60        16 // expected-note {{temporary created here}}
61        );
62  };
63  constexpr const int *address_of(const int &a) {
64    return &a; // expected-note {{pointer to 'n' cannot be returned from a constexpr function}}
65  }
66  constexpr const int *return_param(int n) { // expected-note {{declared here}}
67    return address_of(n); // expected-note {{in call to 'address_of(n)'}}
68  }
69  struct S {
70    int n : *return_param(0); // expected-error {{constant expression}} expected-note {{in call to 'return_param(0)'}}
71  };
72}
73
74// - an invocation of a constexpr constructor with arguments that, when
75//   substituted by function invocation substitution (7.1.5), do not produce all
76//   constant expressions for the constructor calls and full-expressions in the
77//   mem-initializers (including conversions);
78namespace NonConstExprCtor {
79  struct T {
80    constexpr T(const int &r) :
81      r(r) { // expected-note 2{{reference to temporary cannot be used to initialize a member in a constant expression}}
82    }
83    const int &r;
84  };
85  constexpr int n = 0;
86  constexpr T t1(n); // ok
87  constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(0)'}}
88
89  struct S {
90    int n : T(4).r; // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(4)'}}
91  };
92}
93
94// - an invocation of a constexpr function or a constexpr constructor that would
95//   exceed the implementation-defined recursion limits (see Annex B);
96namespace RecursionLimits {
97  constexpr int RecurseForever(int n) {
98    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}}
99  }
100  struct AlsoRecurseForever {
101    constexpr AlsoRecurseForever(int n) :
102      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}}
103    {}
104    int n;
105  };
106  struct S {
107    int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
108    int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
109  };
110}
111
112// - an operation that would have undefined behavior [Note: including, for
113//   example, signed integer overflow (Clause 5 [expr]), certain pointer
114//   arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
115//   shift operations (5.8 [expr.shift]) -end note];
116namespace UndefinedBehavior {
117  void f(int n) {
118    switch (n) {
119    case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
120    case (int)0x80000000u: // ok
121    case (int)10000000000ll: // expected-note {{here}}
122    case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
123    case (int)(unsigned)(long long)4.4e9: // ok
124    case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value 1.0E+300 is outside the range of representable values of type 'float'}}
125    case (int)((float)1e37 / 1e30): // ok
126    case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value 65536 is outside the range of representable values of type 'half'}}
127      break;
128    }
129  }
130
131  constexpr int int_min = ~0x7fffffff;
132  constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
133  constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}}
134  constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}}
135  constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
136  constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
137
138  constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}}
139  constexpr int shl_0 = 0 << 0; // ok
140  constexpr int shl_31 = 0 << 31; // ok
141  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}}
142  constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
143  constexpr int shl_unsigned_into_sign = 1u << 31; // ok
144  constexpr int shl_unsigned_overflow = 1024u << 31; // ok
145  constexpr int shl_signed_negative = (-3) << 1; // expected-error {{constant expression}} expected-note {{left shift of negative value -3}}
146  constexpr int shl_signed_ok = 1 << 30; // ok
147  constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
148  constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
149  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}}
150  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}}
151  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}}
152  constexpr int shl_signed_ok2 = 1024 << 20; // ok
153
154  constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}}
155  constexpr int shr_0 = 0 >> 0; // ok
156  constexpr int shr_31 = 0 >> 31; // ok
157  constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}} expected-warning {{>= width of type}}
158
159  struct S {
160    int m;
161  };
162  constexpr S s = { 5 }; // expected-note {{declared here}}
163  constexpr const int *p = &s.m + 1;
164  constexpr const int &f(const int *q) {
165    return q[0]; // expected-note {{dereferenced pointer past the end of subobject of 's' is not a constant expression}}
166  }
167  constexpr int n = (f(p), 0); // expected-error {{constant expression}} expected-note {{in call to 'f(&s.m + 1)'}}
168  struct T {
169    int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
170  };
171
172  namespace Ptr {
173    struct A {};
174    struct B : A { int n; };
175    B a[3][3];
176    constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
177    B b = {};
178    constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
179    constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
180    constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
181    constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
182
183    constexpr A *na = nullptr;
184    constexpr B *nb = nullptr;
185    constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
186    constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
187    static_assert((A*)nb == 0, "");
188    static_assert((B*)na == 0, "");
189    constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
190    constexpr const int &np = (*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot access array element of null pointer}}
191
192    struct C {
193      constexpr int f() { return 0; }
194    } constexpr c = C();
195    constexpr int k1 = c.f(); // ok
196    constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{cannot call member function on null pointer}}
197    constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{cannot call member function on pointer past the end of object}}
198    C c2;
199    constexpr int k4 = c2.f(); // ok!
200
201    constexpr int diff1 = &a[2] - &a[0];
202    constexpr int diff2 = &a[1][3] - &a[1][0];
203    constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
204    static_assert(&a[2][0] == &a[1][3], "");
205    constexpr int diff4 = (&b + 1) - &b;
206    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}}
207    constexpr int diff6 = &a[1][2].n - &a[1][2].n;
208    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}}
209  }
210
211  namespace Overflow {
212    // Signed int overflow.
213    constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
214    constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
215    constexpr int n3 = n1 + 1; // ok
216    constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
217    constexpr int n5 = -65536 * 32768; // ok
218    constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
219    constexpr int n7 = -n3 + -1; // ok
220    constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
221    constexpr int n9 = n3 - 0; // ok
222    constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
223    constexpr int n11 = -1 - n3; // ok
224    constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
225    constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
226    constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
227    constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
228    constexpr signed char c1 = 100 * 2; // ok
229    constexpr signed char c2 = '\x64' * '\2'; // also ok
230    constexpr long long ll1 = 0x7fffffffffffffff; // ok
231    constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
232    constexpr long long ll3 = -ll1 - 1; // ok
233    constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
234    constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
235
236    // Yikes.
237    char melchizedek[2200000000];
238    typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
239    constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
240    constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
241    constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
242    constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
243
244    // Unsigned int overflow.
245    static_assert(65536u * 65536u == 0u, ""); // ok
246    static_assert(4294967295u + 1u == 0u, ""); // ok
247    static_assert(0u - 1u == 4294967295u, ""); // ok
248    static_assert(~0u * ~0u == 1u, ""); // ok
249
250    // Floating-point overflow and NaN.
251    constexpr float f1 = 1e38f * 3.4028f; // ok
252    constexpr float f2 = 1e38f * 3.4029f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
253    constexpr float f3 = 1e38f / -.2939f; // ok
254    constexpr float f4 = 1e38f / -.2938f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
255    constexpr float f5 = 2e38f + 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
256    constexpr float f6 = -2e38f - 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
257    constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces a NaN}}
258  }
259}
260
261// - a lambda-expression (5.1.2);
262struct Lambda {
263  // FIXME: clang crashes when trying to parse this! Revisit this check once
264  // lambdas are fully implemented.
265  //int n : []{ return 1; }();
266};
267
268// - an lvalue-to-rvalue conversion (4.1) unless it is applied to
269namespace LValueToRValue {
270  // - a non-volatile glvalue of integral or enumeration type that refers to a
271  //   non-volatile const object with a preceding initialization, initialized
272  //   with a constant expression  [Note: a string literal (2.14.5 [lex.string])
273  //   corresponds to an array of such objects. -end note], or
274  volatile const int vi = 1; // expected-note {{here}}
275  const int ci = 1;
276  volatile const int &vrci = ci;
277  static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
278  static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
279  static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
280
281  // - a non-volatile glvalue of literal type that refers to a non-volatile
282  //   object defined with constexpr, or that refers to a sub-object of such an
283  //   object, or
284  struct S {
285    constexpr S(int=0) : i(1), v(1) {}
286    constexpr S(const S &s) : i(2), v(2) {}
287    int i;
288    volatile int v; // expected-note {{here}}
289  };
290  constexpr S s;
291  constexpr volatile S vs; // expected-note {{here}}
292  constexpr const volatile S &vrs = s;
293  static_assert(s.i, "");
294  static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
295  static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile member 'v'}}
296  static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
297  static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
298  static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
299
300  // - a non-volatile glvalue of literal type that refers to a non-volatile
301  //   temporary object whose lifetime has not ended, initialized with a
302  //   constant expression;
303  constexpr volatile S f() { return S(); }
304  static_assert(f().i, ""); // ok! there's no lvalue-to-rvalue conversion here!
305  static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}}
306}
307
308// DR1312: The proposed wording for this defect has issues, so we ignore this
309// bullet and instead prohibit casts from pointers to cv void (see core-20842
310// and core-20845).
311//
312// - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
313// glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
314// are neither the same type nor similar types (4.4 [conv.qual]);
315
316// - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
317// refers to a non-active member of a union or a subobject thereof;
318namespace LValueToRValueUnion {
319  // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
320  // of this.
321  union U { int a, b; } constexpr u = U();
322  static_assert(u.a == 0, "");
323  constexpr const int *bp = &u.b;
324  constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
325
326  extern const U pu;
327  constexpr const int *pua = &pu.a;
328  constexpr const int *pub = &pu.b;
329  constexpr U pu = { .b = 1 }; // expected-warning {{C99 feature}}
330  constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
331  constexpr const int b2 = *pub; // ok
332}
333
334// - an id-expression that refers to a variable or data member of reference type
335//   unless the reference has a preceding initialization, initialized with a
336//   constant expression;
337namespace References {
338  const int a = 2;
339  int &b = *const_cast<int*>(&a);
340  int c = 10; // expected-note 2 {{here}}
341  int &d = c;
342  constexpr int e = 42;
343  int &f = const_cast<int&>(e);
344  extern int &g;
345  constexpr int &h(); // expected-note 2{{here}}
346  int &i = h(); // expected-note {{here}} expected-note {{undefined function 'h' cannot be used in a constant expression}}
347  constexpr int &j() { return b; }
348  int &k = j();
349
350  struct S {
351    int A : a;
352    int B : b;
353    int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
354    int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
355    int D2 : &d - &c + 1;
356    int E : e / 2;
357    int F : f - 11;
358    int G : g; // expected-error {{constant expression}}
359    int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
360    int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
361    int J : j();
362    int K : k;
363  };
364}
365
366// - a dynamic_cast (5.2.7);
367namespace DynamicCast {
368  struct S { int n; };
369  constexpr S s { 16 };
370  struct T {
371    int n : dynamic_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{dynamic_cast}}
372  };
373}
374
375// - a reinterpret_cast (5.2.10);
376namespace ReinterpretCast {
377  struct S { int n; };
378  constexpr S s { 16 };
379  struct T {
380    int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
381  };
382  struct U {
383    int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
384  };
385}
386
387// - a pseudo-destructor call (5.2.4);
388namespace PseudoDtor {
389  int k;
390  typedef int I;
391  struct T {
392    int n : (k.~I(), 0); // expected-error {{constant expression}}
393  };
394}
395
396// - increment or decrement operations (5.2.6, 5.3.2);
397namespace IncDec {
398  int k = 2;
399  struct T {
400    int n : ++k; // expected-error {{constant expression}}
401    int m : --k; // expected-error {{constant expression}}
402  };
403}
404
405// - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
406namespace std {
407  struct type_info {
408    virtual ~type_info();
409    const char *name;
410  };
411}
412namespace TypeId {
413  struct S { virtual void f(); };
414  constexpr S *p = 0;
415  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'}}
416
417  struct T {} t;
418  constexpr const std::type_info &ti2 = typeid(t);
419}
420
421// - a new-expression (5.3.4);
422// - a delete-expression (5.3.5);
423namespace NewDelete {
424  int *p = 0;
425  struct T {
426    int n : *new int(4); // expected-error {{constant expression}}
427    int m : (delete p, 2); // expected-error {{constant expression}}
428  };
429}
430
431// - a relational (5.9) or equality (5.10) operator where the result is
432//   unspecified;
433namespace UnspecifiedRelations {
434  int a, b;
435  constexpr int *p = &a, *q = &b;
436  // C++11 [expr.rel]p2: If two pointers p and q of the same type point to
437  // different objects that are not members of the same array or to different
438  // functions, or if only one of them is null, the results of p<q, p>q, p<=q,
439  // and p>=q are unspecified.
440  constexpr bool u1 = p < q; // expected-error {{constant expression}}
441  constexpr bool u2 = p > q; // expected-error {{constant expression}}
442  constexpr bool u3 = p <= q; // expected-error {{constant expression}}
443  constexpr bool u4 = p >= q; // expected-error {{constant expression}}
444  constexpr bool u5 = p < 0; // expected-error {{constant expression}}
445  constexpr bool u6 = p <= 0; // expected-error {{constant expression}}
446  constexpr bool u7 = p > 0; // expected-error {{constant expression}}
447  constexpr bool u8 = p >= 0; // expected-error {{constant expression}}
448  constexpr bool u9 = 0 < q; // expected-error {{constant expression}}
449  constexpr bool u10 = 0 <= q; // expected-error {{constant expression}}
450  constexpr bool u11 = 0 > q; // expected-error {{constant expression}}
451  constexpr bool u12 = 0 >= q; // expected-error {{constant expression}}
452  void f(), g();
453
454  constexpr void (*pf)() = &f, (*pg)() = &g;
455  constexpr bool u13 = pf < pg; // expected-error {{constant expression}}
456  constexpr bool u14 = pf == pg;
457
458  // If two pointers point to non-static data members of the same object with
459  // different access control, the result is unspecified.
460  struct A {
461  public:
462    constexpr A() : a(0), b(0) {}
463    int a;
464    constexpr bool cmp() { return &a < &b; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{comparison of address of fields 'a' and 'b' of 'A' with differing access specifiers (public vs private) has unspecified value}}
465  private:
466    int b;
467  };
468  class B {
469  public:
470    A a;
471    constexpr bool cmp() { return &a.a < &b.a; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{comparison of address of fields 'a' and 'b' of 'B' with differing access specifiers (public vs protected) has unspecified value}}
472  protected:
473    A b;
474  };
475
476  // If two pointers point to different base sub-objects of the same object, or
477  // one points to a base subobject and the other points to a member, the result
478  // of the comparison is unspecified. This is not explicitly called out by
479  // [expr.rel]p2, but is covered by 'Other pointer comparisons are
480  // unspecified'.
481  struct C {
482    int c[2];
483  };
484  struct D {
485    int d;
486  };
487  struct E : C, D {
488    struct Inner {
489      int f;
490    } e;
491  } e;
492  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}}
493  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}}
494  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}}
495
496  // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
497  // represent the same address or are both the null pointer [...]; otherwise
498  // the result is unspecified.
499  struct S { int a, b; } s;
500  constexpr void *null = 0;
501  constexpr void *pv = (void*)&s.a;
502  constexpr void *qv = (void*)&s.b;
503  constexpr bool v1 = null < 0;
504  constexpr bool v2 = null < pv; // expected-error {{constant expression}}
505  constexpr bool v3 = null == pv; // ok
506  constexpr bool v4 = qv == pv; // ok
507  constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
508  constexpr bool v6 = qv > null; // expected-error {{constant expression}}
509  constexpr bool v7 = qv <= (void*)&s.b; // ok
510  constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
511}
512
513// - an assignment or a compound assignment (5.17); or
514namespace Assignment {
515  int k;
516  struct T {
517    int n : (k = 9); // expected-error {{constant expression}}
518    int m : (k *= 2); // expected-error {{constant expression}}
519  };
520
521  struct Literal {
522    constexpr Literal(const char *name) : name(name) {}
523    const char *name;
524  };
525  struct Expr {
526    constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
527    bool IsLiteral;
528    union {
529      Literal l;
530      // ...
531    };
532  };
533  struct MulEq {
534    constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
535    Expr LHS;
536    Expr RHS;
537  };
538  constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
539  Literal a("a");
540  Literal b("b");
541  MulEq c = a *= b; // ok
542}
543
544// - a throw-expression (15.1)
545namespace Throw {
546  struct S {
547    int n : (throw "hello", 10); // expected-error {{constant expression}}
548  };
549}
550
551// PR9999
552template<unsigned int v>
553class bitWidthHolding {
554public:
555  static const
556  unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
557};
558
559static const int width=bitWidthHolding<255>::width;
560
561template<bool b>
562struct always_false {
563  static const bool value = false;
564};
565
566template<bool b>
567struct and_or {
568  static const bool and_value = b && and_or<always_false<b>::value>::and_value;
569  static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
570};
571
572static const bool and_value = and_or<true>::and_value;
573static const bool or_value = and_or<true>::or_value;
574
575static_assert(and_value == false, "");
576static_assert(or_value == true, "");
577