p2-0x.cpp revision 26dc97cbeba8ced19972a259720a71aefa01ef43 
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 core constant
53//   expression;
54namespace 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);
76namespace 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);
94namespace 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
111namespace 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&() { 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];
131namespace 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'}} expected-note {{previous case defined here}}
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'}} expected-error {{duplicate case value '2147483647'}} expected-note {{previous case defined here}}
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 'half'}} expected-error {{duplicate case value '2147483647'}}
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-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 &np = (*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot access array element of null pointer}}
206
207    struct C {
208      constexpr int f() { return 0; }
209    } constexpr c = C();
210    constexpr int k1 = c.f(); // ok
211    constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{cannot call member function on null pointer}}
212    constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{cannot call member function on pointer past the end of object}}
213    C c2;
214    constexpr int k4 = c2.f(); // ok!
215
216    constexpr int diff1 = &a[2] - &a[0];
217    constexpr int diff2 = &a[1][3] - &a[1][0];
218    constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
219    static_assert(&a[2][0] == &a[1][3], "");
220    constexpr int diff4 = (&b + 1) - &b;
221    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}}
222    constexpr int diff6 = &a[1][2].n - &a[1][2].n;
223    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}}
224  }
225
226  namespace Overflow {
227    // Signed int overflow.
228    constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
229    constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
230    constexpr int n3 = n1 + 1; // ok
231    constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
232    constexpr int n5 = -65536 * 32768; // ok
233    constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
234    constexpr int n7 = -n3 + -1; // ok
235    constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
236    constexpr int n9 = n3 - 0; // ok
237    constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
238    constexpr int n11 = -1 - n3; // ok
239    constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
240    constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
241    constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
242    constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
243    constexpr signed char c1 = 100 * 2; // ok
244    constexpr signed char c2 = '\x64' * '\2'; // also ok
245    constexpr long long ll1 = 0x7fffffffffffffff; // ok
246    constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
247    constexpr long long ll3 = -ll1 - 1; // ok
248    constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
249    constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
250
251    // Yikes.
252    char melchizedek[2200000000];
253    typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
254    constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
255    constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
256    constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
257    constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
258
259    // Unsigned int overflow.
260    static_assert(65536u * 65536u == 0u, ""); // ok
261    static_assert(4294967295u + 1u == 0u, ""); // ok
262    static_assert(0u - 1u == 4294967295u, ""); // ok
263    static_assert(~0u * ~0u == 1u, ""); // ok
264
265    // Floating-point overflow and NaN.
266    constexpr float f1 = 1e38f * 3.4028f; // ok
267    constexpr float f2 = 1e38f * 3.4029f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
268    constexpr float f3 = 1e38f / -.2939f; // ok
269    constexpr float f4 = 1e38f / -.2938f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
270    constexpr float f5 = 2e38f + 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
271    constexpr float f6 = -2e38f - 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}}
272    constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces a NaN}}
273  }
274}
275
276// - a lambda-expression (5.1.2);
277struct Lambda {
278  // FIXME: clang crashes when trying to parse this! Revisit this check once
279  // lambdas are fully implemented.
280  //int n : []{ return 1; }();
281};
282
283// - an lvalue-to-rvalue conversion (4.1) unless it is applied to
284namespace 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}}
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;
338namespace 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;
357namespace 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);
387namespace 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);
396namespace 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);
408namespace 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);
417namespace 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;
426namespace std {
427  struct type_info {
428    virtual ~type_info();
429    const char *name;
430  };
431}
432namespace 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);
443namespace 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;
453namespace 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() { 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}}
485  private:
486    int b;
487  };
488  class B {
489  public:
490    A a;
491    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}}
492  protected:
493    A b;
494  };
495
496  // If two pointers point to different base sub-objects of the same object, or
497  // one points to a base subobject and the other points to a member, the result
498  // of the comparison is unspecified. This is not explicitly called out by
499  // [expr.rel]p2, but is covered by 'Other pointer comparisons are
500  // unspecified'.
501  struct C {
502    int c[2];
503  };
504  struct D {
505    int d;
506  };
507  struct E : C, D {
508    struct Inner {
509      int f;
510    } e;
511  } e;
512  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}}
513  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}}
514  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}}
515
516  // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
517  // represent the same address or are both the null pointer [...]; otherwise
518  // the result is unspecified.
519  struct S { int a, b; } s;
520  constexpr void *null = 0;
521  constexpr void *pv = (void*)&s.a;
522  constexpr void *qv = (void*)&s.b;
523  constexpr bool v1 = null < 0;
524  constexpr bool v2 = null < pv; // expected-error {{constant expression}}
525  constexpr bool v3 = null == pv; // ok
526  constexpr bool v4 = qv == pv; // ok
527  constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
528  constexpr bool v6 = qv > null; // expected-error {{constant expression}}
529  constexpr bool v7 = qv <= (void*)&s.b; // ok
530  constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
531}
532
533// - an assignment or a compound assignment (5.17); or
534namespace Assignment {
535  int k;
536  struct T {
537    int n : (k = 9); // expected-error {{constant expression}}
538    int m : (k *= 2); // expected-error {{constant expression}}
539  };
540
541  struct Literal {
542    constexpr Literal(const char *name) : name(name) {}
543    const char *name;
544  };
545  struct Expr {
546    constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
547    bool IsLiteral;
548    union {
549      Literal l;
550      // ...
551    };
552  };
553  struct MulEq {
554    constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
555    Expr LHS;
556    Expr RHS;
557  };
558  constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
559  Literal a("a");
560  Literal b("b");
561  MulEq c = a *= b; // ok
562}
563
564// - a throw-expression (15.1)
565namespace Throw {
566  struct S {
567    int n : (throw "hello", 10); // expected-error {{constant expression}}
568  };
569}
570
571// PR9999
572template<unsigned int v>
573class bitWidthHolding {
574public:
575  static const
576  unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
577};
578
579static const int width=bitWidthHolding<255>::width;
580
581template<bool b>
582struct always_false {
583  static const bool value = false;
584};
585
586template<bool b>
587struct and_or {
588  static const bool and_value = b && and_or<always_false<b>::value>::and_value;
589  static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
590};
591
592static const bool and_value = and_or<true>::and_value;
593static const bool or_value = and_or<true>::or_value;
594
595static_assert(and_value == false, "");
596static_assert(or_value == true, "");
597