1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify=expected,cxx11 -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu
2 // RUN: %clang_cc1 -fsyntax-only -std=c++2a -pedantic -verify=expected,cxx20 -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu
3 
4 // A conditional-expression is a core constant expression unless it involves one
5 // of the following as a potentially evaluated subexpression [...]:
6 
7 // - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant
8 //   expression, function invocation substitution (7.1.5 [dcl.constexpr])
9 //   replaces each occurrence of this in a constexpr member function with a
10 //   pointer to the class object. -end note];
11 struct This {
12   int this1 : this1; // expected-error {{undeclared}}
13   int this2 : this->this1; // expected-error {{invalid}}
14   void this3() {
15     int n1[this->this1]; // expected-warning {{variable length array}}
16     int n2[this1]; // expected-warning {{variable length array}}
17     (void)n1, (void)n2;
18   }
19 };
20 
21 // - an invocation of a function other than a constexpr constructor for a
22 //   literal class or a constexpr function [ Note: Overload resolution (13.3)
23 //   is applied as usual - end note ];
24 struct NonConstexpr1 {
25   static int f() { return 1; } // expected-note {{here}}
26   int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
27 };
28 struct NonConstexpr2 {
29   constexpr NonConstexpr2(); // expected-note {{here}}
30   int n;
31 };
32 struct NonConstexpr3 {
33   NonConstexpr3();
34   int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
35 };
36 struct NonConstexpr4 {
37   NonConstexpr4();
38   int n;
39 };
40 struct NonConstexpr5 {
41   int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-literal type 'NonConstexpr4' cannot be used in a constant expression}}
42 };
43 
44 // - an invocation of an undefined constexpr function or an undefined
45 //   constexpr constructor;
46 struct UndefinedConstexpr {
47   constexpr UndefinedConstexpr();
48   static constexpr int undefinedConstexpr1(); // expected-note {{here}}
49   int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}}
50 };
51 
52 // - an invocation of a constexpr function with arguments that, when substituted
53 //   by function invocation substitution (7.1.5), do not produce a core constant
54 //   expression;
55 namespace NonConstExprReturn {
56   static constexpr const int &id_ref(const int &n) {
57     return n;
58   }
59   struct NonConstExprFunction {
60     int n : id_ref(16); // ok
61   };
62   constexpr const int *address_of(const int &a) {
63     return &a;
64   }
65   constexpr const int *return_param(int n) { // expected-note {{declared here}}
66     return address_of(n);
67   }
68   struct S {
69     int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of variable whose lifetime has ended}}
70   };
71 }
72 
73 // - an invocation of a constexpr constructor with arguments that, when
74 //   substituted by function invocation substitution (7.1.5), do not produce all
75 //   constant expressions for the constructor calls and full-expressions in the
76 //   mem-initializers (including conversions);
77 namespace NonConstExprCtor {
78   struct T {
79     constexpr T(const int &r) :
80       r(r) {
81     }
82     const int &r;
83   };
84   constexpr int n = 0;
85   constexpr T t1(n); // ok
86   constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{reference to temporary is not a constant expression}}
87 
88   struct S {
89     int n : T(4).r; // ok
90   };
91 }
92 
93 // - an invocation of a constexpr function or a constexpr constructor that would
94 //   exceed the implementation-defined recursion limits (see Annex B);
95 namespace RecursionLimits {
96   constexpr int RecurseForever(int n) {
97     return n + RecurseForever(n+1); // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'RecurseForever(}} expected-note {{skipping 118 calls}}
98   }
99   struct AlsoRecurseForever {
100     constexpr AlsoRecurseForever(int n) :
101       n(AlsoRecurseForever(n+1).n) // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'AlsoRecurseForever(}} expected-note {{skipping 118 calls}}
102     {}
103     int n;
104   };
105   struct S {
106     int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
107     int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
108   };
109 }
110 
111 // DR1458: taking the address of an object of incomplete class type
112 namespace IncompleteClassTypeAddr {
113   struct S;
114   extern S s;
115   constexpr S *p = &s; // ok
116   static_assert(p, "");
117 
118   extern S sArr[];
119   constexpr S (*p2)[] = &sArr; // ok
120 
121   struct S {
122     constexpr S *operator&() const { return nullptr; }
123   };
124   constexpr S *q = &s; // ok
125   static_assert(!q, "");
126 }
127 
128 // - an operation that would have undefined behavior [Note: including, for
129 //   example, signed integer overflow (Clause 5 [expr]), certain pointer
130 //   arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
131 //   shift operations (5.8 [expr.shift]) -end note];
132 namespace UndefinedBehavior {
133   void f(int n) {
134     switch (n) {
135     case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
136     case (int)0x80000000u: // ok
137     case (int)10000000000ll: // expected-note {{here}}
138     case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
139     case (int)(unsigned)(long long)4.4e9: // ok
140     case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
141     case (int)((float)1e37 / 1e30): // ok
142     case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
143       break;
144     }
145   }
146 
147   constexpr int int_min = ~0x7fffffff;
148   constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
149   constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}}
150   constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}}
151   constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
152   constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
153 
154   constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
155   constexpr int shl_0 = 0 << 0; // ok
156   constexpr int shl_31 = 0 << 31; // ok
157   constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}}
158   constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
159   constexpr int shl_unsigned_into_sign = 1u << 31; // ok
160   constexpr int shl_unsigned_overflow = 1024u << 31; // ok
161   constexpr int shl_signed_negative = (-3) << 1; // cxx11-error {{constant expression}} cxx11-note {{left shift of negative value -3}}
162   constexpr int shl_signed_ok = 1 << 30; // ok
163   constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
164   constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
165   constexpr int shl_signed_off_end = 2 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}}
166   constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}}
167   constexpr int shl_signed_overflow = 1024 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} expected-warning {{requires 43 bits to represent}}
168   constexpr int shl_signed_ok2 = 1024 << 20; // ok
169 
170   constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
171   constexpr int shr_0 = 0 >> 0; // ok
172   constexpr int shr_31 = 0 >> 31; // ok
173   constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}}
174 
175   struct S {
176     int m;
177   };
178   constexpr S s = { 5 };
179   constexpr const int *p = &s.m + 1;
180   constexpr const int &f(const int *q) {
181     return q[0];
182   }
183   constexpr int n = (f(p), 0); // ok
184   struct T {
185     int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
186   };
187 
188   namespace Ptr {
189     struct A {};
190     struct B : A { int n; };
191     B a[3][3];
192     constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
193     B b = {};
194     constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
195     constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
196     constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
197     constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
198 
199     constexpr A *na = nullptr;
200     constexpr B *nb = nullptr;
201     constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
202     constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
203     static_assert((A*)nb == 0, "");
204     static_assert((B*)na == 0, "");
205     constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
206     constexpr const int *np1 = (int*)nullptr + 0; // ok
207     constexpr const int *np2 = &(*(int(*)[4])nullptr)[0]; // ok
208     constexpr const int *np3 = &(*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot perform pointer arithmetic on null pointer}}
209 
210     struct C {
211       constexpr int f() const { return 0; }
212     } constexpr c = C();
213     constexpr int k1 = c.f(); // ok
214     constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced null pointer}}
215     constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced one-past-the-end pointer}}
216     C c2;
217     constexpr int k4 = c2.f(); // ok!
218 
219     constexpr int diff1 = &a[2] - &a[0];
220     constexpr int diff2 = &a[1][3] - &a[1][0];
221     constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
222     static_assert(&a[2][0] == &a[1][3], "");
223     constexpr int diff4 = (&b + 1) - &b;
224     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}}
225     constexpr int diff6 = &a[1][2].n - &a[1][2].n;
226     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}}
227   }
228 
229   namespace Overflow {
230     // Signed int overflow.
231     constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
232     constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
233     constexpr int n3 = n1 + 1; // ok
234     constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
235     constexpr int n5 = -65536 * 32768; // ok
236     constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
237     constexpr int n7 = -n3 + -1; // ok
238     constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
239     constexpr int n9 = n3 - 0; // ok
240     constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
241     constexpr int n11 = -1 - n3; // ok
242     constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
243     constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
244     constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
245     constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
246     constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
247     constexpr signed char c2 = '\x64' * '\2'; // also ok  expected-warning{{changes value}}
248     constexpr long long ll1 = 0x7fffffffffffffff; // ok
249     constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
250     constexpr long long ll3 = -ll1 - 1; // ok
251     constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
252     constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
253 
254     // Yikes.
255     char melchizedek[2200000000];
256     typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
257     constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
258     constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
259     constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
260     constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
261 
262     // Unsigned int overflow.
263     static_assert(65536u * 65536u == 0u, ""); // ok
264     static_assert(4294967295u + 1u == 0u, ""); // ok
265     static_assert(0u - 1u == 4294967295u, ""); // ok
266     static_assert(~0u * ~0u == 1u, ""); // ok
267 
268     template<typename T> constexpr bool isinf(T v) { return v && v / 2 == v; }
269 
270     // Floating-point overflow and NaN.
271     constexpr float f1 = 1e38f * 3.4028f; // ok
272     constexpr float f2 = 1e38f * 3.4029f; // ok, +inf is in range of representable values
273     constexpr float f3 = 1e38f / -.2939f; // ok
274     constexpr float f4 = 1e38f / -.2938f; // ok, -inf is in range of representable values
275     constexpr float f5 = 2e38f + 2e38f; // ok, +inf is in range of representable values
276     constexpr float f6 = -2e38f - 2e38f; // ok, -inf is in range of representable values
277     constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
278     constexpr float f8 = 1.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
279     constexpr float f9 = 1e308 / 1e-308; // ok, +inf
280     constexpr float f10 = f2 - f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
281     constexpr float f11 = f2 + f4; // expected-error {{constant expression}} expected-note {{produces a NaN}}
282     constexpr float f12 = f2 / f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
283     static_assert(!isinf(f1), "");
284     static_assert(isinf(f2), "");
285     static_assert(!isinf(f3), "");
286     static_assert(isinf(f4), "");
287     static_assert(isinf(f5), "");
288     static_assert(isinf(f6), "");
289     static_assert(isinf(f9), "");
290   }
291 }
292 
293 // - a lambda-expression (5.1.2);
294 struct Lambda {
295   int n : []{ return 1; }(); // cxx11-error {{constant expression}} cxx11-error {{integral constant expression}} cxx11-note {{non-literal type}}
296 };
297 
298 // - an lvalue-to-rvalue conversion (4.1) unless it is applied to
299 namespace LValueToRValue {
300   // - a non-volatile glvalue of integral or enumeration type that refers to a
301   //   non-volatile const object with a preceding initialization, initialized
302   //   with a constant expression  [Note: a string literal (2.14.5 [lex.string])
303   //   corresponds to an array of such objects. -end note], or
304   volatile const int vi = 1; // expected-note 2{{here}}
305   const int ci = 1;
306   volatile const int &vrci = ci;
307   static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
308   static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
309   static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
310 
311   // - a non-volatile glvalue of literal type that refers to a non-volatile
312   //   object defined with constexpr, or that refers to a sub-object of such an
313   //   object, or
314   struct V {
315     constexpr V() : v(1) {}
316     volatile int v; // expected-note {{not literal because}}
317   };
318   constexpr V v; // expected-error {{non-literal type}}
319   struct S {
320     constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
321     constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {}
322     int i;
323     volatile int &v;
324   };
325   constexpr S s; // ok
326   constexpr volatile S vs; // expected-note {{here}}
327   constexpr const volatile S &vrs = s; // ok
328   static_assert(s.i, "");
329   static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
330   static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
331   static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
332   static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
333   static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
334 
335   // - a non-volatile glvalue of literal type that refers to a non-volatile
336   //   temporary object whose lifetime has not ended, initialized with a
337   //   constant expression;
338   constexpr volatile S f() { return S(); }
339   static_assert(f().i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
340   static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
341 }
342 
343 // DR1312: The proposed wording for this defect has issues, so we ignore this
344 // bullet and instead prohibit casts from pointers to cv void (see core-20842
345 // and core-20845).
346 //
347 // - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
348 // glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
349 // are neither the same type nor similar types (4.4 [conv.qual]);
350 
351 // - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
352 // refers to a non-active member of a union or a subobject thereof;
353 namespace LValueToRValueUnion {
354   // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
355   // of this.
356   union U { int a, b; } constexpr u = U();
357   static_assert(u.a == 0, "");
358   constexpr const int *bp = &u.b;
359   constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
360 
361   extern const U pu;
362   constexpr const int *pua = &pu.a;
363   constexpr const int *pub = &pu.b;
364   constexpr U pu = { .b = 1 }; // cxx11-warning {{C++20 extension}}
365   constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
366   constexpr const int b2 = *pub; // ok
367 }
368 
369 // - an id-expression that refers to a variable or data member of reference type
370 //   unless the reference has a preceding initialization, initialized with a
371 //   constant expression;
372 namespace References {
373   const int a = 2;
374   int &b = *const_cast<int*>(&a);
375   int c = 10; // expected-note 2 {{here}}
376   int &d = c;
377   constexpr int e = 42;
378   int &f = const_cast<int&>(e);
379   extern int &g; // expected-note {{here}}
380   constexpr int &h(); // expected-note {{here}}
381   int &i = h(); // expected-note {{here}}
382   constexpr int &j() { return b; }
383   int &k = j();
384 
385   struct S {
386     int A : a;
387     int B : b;
388     int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
389     int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
390     int D2 : &d - &c + 1;
391     int E : e / 2;
392     int F : f - 11;
393     int G : g; // expected-error {{constant expression}} expected-note {{initializer of 'g' is unknown}}
394     int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
395     int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
396     int J : j();
397     int K : k;
398   };
399 }
400 
401 // - a dynamic_cast (5.2.7);
402 namespace DynamicCast {
403   struct S { int n; };
404   constexpr S s { 16 };
405   struct T {
406     int n : dynamic_cast<const S*>(&s)->n; // cxx11-warning {{constant expression}} cxx11-note {{dynamic_cast}}
407   };
408 }
409 
410 // - a reinterpret_cast (5.2.10);
411 namespace ReinterpretCast {
412   struct S { int n; };
413   constexpr S s { 16 };
414   struct T {
415     int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
416   };
417   struct U {
418     int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
419   };
420 }
421 
422 // - a pseudo-destructor call (5.2.4);
423 namespace PseudoDtor {
424   int k;
425   typedef int I;
426   struct T {
427     int n : (k.~I(), 1); // expected-error {{constant expression}} expected-note {{visible outside that expression}}
428   };
429 
430   // FIXME: It's unclear whether this should be accepted in C++20 mode. The parameter is destroyed twice here.
431   constexpr int f(int a = 1) { // cxx11-error {{constant expression}}
432     return (
433         a.~I(), // cxx11-note 2{{pseudo-destructor}}
434         0);
435   }
436   static_assert(f() == 0, ""); // cxx11-error {{constant expression}} cxx11-note {{in call}}
437 
438   // This is OK in C++20: the union has no active member after the
439   // pseudo-destructor call, so the union destructor has no effect.
440   union U { int x; };
441   constexpr int g(U u = {1}) { // cxx11-error {{constant expression}}
442     return (
443         u.x.~I(), // cxx11-note 2{{pseudo-destructor}}
444         0);
445   }
446   static_assert(g() == 0, ""); // cxx11-error {{constant expression}} cxx11-note {{in call}}
447 }
448 
449 // - increment or decrement operations (5.2.6, 5.3.2);
450 namespace IncDec {
451   int k = 2;
452   struct T {
453     int n : ++k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
454     int m : --k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
455   };
456 }
457 
458 // - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
459 namespace std {
460   struct type_info {
461     virtual ~type_info();
462     const char *name;
463   };
464 }
465 namespace TypeId {
466   struct S { virtual void f(); };
467   constexpr S *p = 0;
468   constexpr const std::type_info &ti1 = typeid(*p); // expected-error {{must be initialized by a constant expression}} cxx11-note {{typeid applied to expression of polymorphic type 'TypeId::S'}} cxx20-note {{dereferenced null pointer}}
469 
470   struct T {} t;
471   constexpr const std::type_info &ti2 = typeid(t);
472 }
473 
474 // - a new-expression (5.3.4);
475 // - a delete-expression (5.3.5);
476 namespace NewDelete {
477   constexpr int *p = 0;
478   struct T {
479     int n : *new int(4); // expected-warning {{constant expression}} cxx11-note {{until C++20}} cxx20-note {{was not deallocated}}
480     int m : (delete p, 2); // cxx11-warning {{constant expression}} cxx11-note {{until C++20}}
481   };
482 }
483 
484 // - a relational (5.9) or equality (5.10) operator where the result is
485 //   unspecified;
486 namespace UnspecifiedRelations {
487   int a, b;
488   constexpr int *p = &a, *q = &b;
489   // C++11 [expr.rel]p2: If two pointers p and q of the same type point to
490   // different objects that are not members of the same array or to different
491   // functions, or if only one of them is null, the results of p<q, p>q, p<=q,
492   // and p>=q are unspecified.
493   constexpr bool u1 = p < q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
494   constexpr bool u2 = p > q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
495   constexpr bool u3 = p <= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
496   constexpr bool u4 = p >= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
497   constexpr bool u5 = p < (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
498   constexpr bool u6 = p <= (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
499   constexpr bool u7 = p > (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
500   constexpr bool u8 = p >= (int*)0; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
501   constexpr bool u9 = (int*)0 < q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
502   constexpr bool u10 = (int*)0 <= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
503   constexpr bool u11 = (int*)0 > q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
504   constexpr bool u12 = (int*)0 >= q; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
505   void f(), g();
506 
507   constexpr void (*pf)() = &f, (*pg)() = &g;
508   constexpr bool u13 = pf < pg; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
509   constexpr bool u14 = pf == pg;
510 
511   // If two pointers point to non-static data members of the same object with
512   // different access control, the result is unspecified.
513   struct A {
514   public:
515     constexpr A() : a(0), b(0) {}
516     int a;
517     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}}
518   private:
519     int b;
520   };
521   static_assert(A().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
522   class B {
523   public:
524     A a;
525     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}}
526   protected:
527     A b;
528   };
529   static_assert(B().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
530 
531   // If two pointers point to different base sub-objects of the same object, or
532   // one points to a base subobject and the other points to a member, the result
533   // of the comparison is unspecified. This is not explicitly called out by
534   // [expr.rel]p2, but is covered by 'Other pointer comparisons are
535   // unspecified'.
536   struct C {
537     int c[2];
538   };
539   struct D {
540     int d;
541   };
542   struct E : C, D {
543     struct Inner {
544       int f;
545     } e;
546   } e;
547   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}}
548   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}}
549   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}}
550 
551   // [expr.rel]p3: Pointers to void can be compared [...] if both pointers
552   // represent the same address or are both the null pointer [...]; otherwise
553   // the result is unspecified.
554   struct S { int a, b; } s;
555   constexpr void *null = 0;
556   constexpr void *pv = (void*)&s.a;
557   constexpr void *qv = (void*)&s.b;
558   constexpr bool v1 = null < (int*)0;
559   constexpr bool v2 = null < pv; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
560   constexpr bool v3 = null == pv; // ok
561   constexpr bool v4 = qv == pv; // ok
562   constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
563   constexpr bool v6 = qv > null; // expected-error {{constant expression}} expected-note {{comparison has unspecified value}}
564   constexpr bool v7 = qv <= (void*)&s.b; // ok
565   constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}}
566 }
567 
568 // - an assignment or a compound assignment (5.17); or
569 namespace Assignment {
570   int k;
571   struct T {
572     int n : (k = 9); // expected-error {{constant expression}} cxx20-note {{visible outside}}
573     int m : (k *= 2); // expected-error {{constant expression}} cxx20-note {{visible outside}}
574   };
575 
576   struct Literal {
577     constexpr Literal(const char *name) : name(name) {}
578     const char *name;
579   };
580   struct Expr {
581     constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
582     bool IsLiteral;
583     union {
584       Literal l;
585       // ...
586     };
587   };
588   struct MulEq {
589     constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
590     Expr LHS;
591     Expr RHS;
592   };
593   constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
594   Literal a("a");
595   Literal b("b");
596   MulEq c = a *= b; // ok
597 }
598 
599 // - a throw-expression (15.1)
600 namespace Throw {
601   struct S {
602     int n : (throw "hello", 10); // expected-error {{constant expression}}
603   };
604 }
605 
606 // PR9999
607 template<unsigned int v>
608 class bitWidthHolding {
609 public:
610   static const
611   unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
612 };
613 
614 static const int width=bitWidthHolding<255>::width;
615 
616 template<bool b>
617 struct always_false {
618   static const bool value = false;
619 };
620 
621 template<bool b>
622 struct and_or {
623   static const bool and_value = b && and_or<always_false<b>::value>::and_value;
624   static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
625 };
626 
627 static const bool and_value = and_or<true>::and_value;
628 static const bool or_value = and_or<true>::or_value;
629 
630 static_assert(and_value == false, "");
631 static_assert(or_value == true, "");
632 
633 namespace rdar13090123 {
634   typedef __INTPTR_TYPE__ intptr_t;
635 
636   constexpr intptr_t f(intptr_t x) {
637     return (((x) >> 21) * 8);
638   }
639 
640   extern "C" int foo;
641 
642   constexpr intptr_t i = f((intptr_t)&foo - 10); // expected-error{{constexpr variable 'i' must be initialized by a constant expression}} \
643   // expected-note{{reinterpret_cast}}
644 }
645