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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}}
this3This13   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 {
fNonConstexpr124   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 {
id_ref(const int & n)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   };
address_of(const int & a)61   constexpr const int *address_of(const int &a) {
62     return &a;
63   }
return_param(int n)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 {
TNonConstExprCtor::T78     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 {
RecurseForever(int n)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 {
AlsoRecurseForeverRecursionLimits::AlsoRecurseForever99     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 {
operator &IncompleteClassTypeAddr::S121     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 {
f(int n)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;
f(const int * q)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 {
fUndefinedBehavior::Ptr::C210       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 {
__anon905e1dd40102Lambda280   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 {
VLValueToRValue::V300     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 {
SLValueToRValue::S305     constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
SLValueToRValue::S306     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;
f()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}}
j()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:
AUnspecifiedRelations::A482     constexpr A() : a(0), b(0) {}
483     int a;
cmpUnspecifiedRelations::A484     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;
cmp() const492     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 {
LiteralAssignment::Literal544     constexpr Literal(const char *name) : name(name) {}
545     const char *name;
546   };
547   struct Expr {
ExprAssignment::Expr548     constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
549     bool IsLiteral;
550     union {
551       Literal l;
552       // ...
553     };
554   };
555   struct MulEq {
MulEqAssignment::MulEq556     constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
557     Expr LHS;
558     Expr RHS;
559   };
operator *=(Expr a,Expr b)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 
f(intptr_t x)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