constant-expression-cxx11.cpp revision 86024013d4c3728122c58fa07a2a67e6c15837ef 
1// RUN: %clang_cc1 -triple i686-linux -fsyntax-only -verify -std=c++11 -pedantic %s -Wno-comment
2
3namespace StaticAssertFoldTest {
4
5int x;
6static_assert(++x, "test"); // expected-error {{not an integral constant expression}}
7static_assert(false, "test"); // expected-error {{test}}
8
9}
10
11typedef decltype(sizeof(char)) size_t;
12
13template<typename T> constexpr T id(const T &t) { return t; }
14template<typename T> constexpr T min(const T &a, const T &b) {
15  return a < b ? a : b;
16}
17template<typename T> constexpr T max(const T &a, const T &b) {
18  return a < b ? b : a;
19}
20template<typename T, size_t N> constexpr T *begin(T (&xs)[N]) { return xs; }
21template<typename T, size_t N> constexpr T *end(T (&xs)[N]) { return xs + N; }
22
23struct MemberZero {
24  constexpr int zero() { return 0; }
25};
26
27namespace DerivedToVBaseCast {
28
29  struct U { int n; };
30  struct V : U { int n; };
31  struct A : virtual V { int n; };
32  struct Aa { int n; };
33  struct B : virtual A, Aa {};
34  struct C : virtual A, Aa {};
35  struct D : B, C {};
36
37  D d;
38  constexpr B *p = &d;
39  constexpr C *q = &d;
40
41  static_assert((void*)p != (void*)q, "");
42  static_assert((A*)p == (A*)q, "");
43  static_assert((Aa*)p != (Aa*)q, "");
44
45  constexpr B &pp = d;
46  constexpr C &qq = d;
47  static_assert((void*)&pp != (void*)&qq, "");
48  static_assert(&(A&)pp == &(A&)qq, "");
49  static_assert(&(Aa&)pp != &(Aa&)qq, "");
50
51  constexpr V *v = p;
52  constexpr V *w = q;
53  constexpr V *x = (A*)p;
54  static_assert(v == w, "");
55  static_assert(v == x, "");
56
57  static_assert((U*)&d == p, "");
58  static_assert((U*)&d == q, "");
59  static_assert((U*)&d == v, "");
60  static_assert((U*)&d == w, "");
61  static_assert((U*)&d == x, "");
62
63  struct X {};
64  struct Y1 : virtual X {};
65  struct Y2 : X {};
66  struct Z : Y1, Y2 {};
67  Z z;
68  static_assert((X*)(Y1*)&z != (X*)(Y2*)&z, "");
69}
70
71namespace ConstCast {
72
73constexpr int n1 = 0;
74constexpr int n2 = const_cast<int&>(n1);
75constexpr int *n3 = const_cast<int*>(&n1);
76constexpr int n4 = *const_cast<int*>(&n1);
77constexpr const int * const *n5 = const_cast<const int* const*>(&n3);
78constexpr int **n6 = const_cast<int**>(&n3);
79constexpr int n7 = **n5;
80constexpr int n8 = **n6;
81
82}
83
84namespace TemplateArgumentConversion {
85  template<int n> struct IntParam {};
86
87  using IntParam0 = IntParam<0>;
88  using IntParam0 = IntParam<id(0)>;
89  using IntParam0 = IntParam<MemberZero().zero>; // expected-error {{did you mean to call it with no arguments?}}
90}
91
92namespace CaseStatements {
93  void f(int n) {
94    switch (n) {
95    case MemberZero().zero: // expected-error {{did you mean to call it with no arguments?}} expected-note {{previous}}
96    case id(0): // expected-error {{duplicate case value '0'}}
97      return;
98    }
99  }
100}
101
102extern int &Recurse1;
103int &Recurse2 = Recurse1; // expected-note 2{{declared here}} expected-note {{initializer of 'Recurse1' is not a constant expression}}
104int &Recurse1 = Recurse2; // expected-note {{declared here}} expected-note {{initializer of 'Recurse2' is not a constant expression}}
105constexpr int &Recurse3 = Recurse2; // expected-error {{must be initialized by a constant expression}} expected-note {{initializer of 'Recurse2' is not a constant expression}}
106
107extern const int RecurseA;
108const int RecurseB = RecurseA; // expected-note {{declared here}}
109const int RecurseA = 10;
110constexpr int RecurseC = RecurseB; // expected-error {{must be initialized by a constant expression}} expected-note {{initializer of 'RecurseB' is not a constant expression}}
111
112namespace MemberEnum {
113  struct WithMemberEnum {
114    enum E { A = 42 };
115  } wme;
116
117  static_assert(wme.A == 42, "");
118}
119
120namespace DefaultArguments {
121
122const int z = int();
123constexpr int Sum(int a = 0, const int &b = 0, const int *c = &z, char d = 0) {
124  return a + b + *c + d;
125}
126const int four = 4;
127constexpr int eight = 8;
128constexpr const int twentyseven = 27;
129static_assert(Sum() == 0, "");
130static_assert(Sum(1) == 1, "");
131static_assert(Sum(1, four) == 5, "");
132static_assert(Sum(1, eight, &twentyseven) == 36, "");
133static_assert(Sum(1, 2, &four, eight) == 15, "");
134
135}
136
137namespace Ellipsis {
138
139// Note, values passed through an ellipsis can't actually be used.
140constexpr int F(int a, ...) { return a; }
141static_assert(F(0) == 0, "");
142static_assert(F(1, 0) == 1, "");
143static_assert(F(2, "test") == 2, "");
144static_assert(F(3, &F) == 3, "");
145int k = 0; // expected-note {{here}}
146static_assert(F(4, k) == 3, ""); // expected-error {{constant expression}} expected-note {{read of non-const variable 'k'}}
147
148}
149
150namespace Recursion {
151  constexpr int fib(int n) { return n > 1 ? fib(n-1) + fib(n-2) : n; }
152  static_assert(fib(11) == 89, "");
153
154  constexpr int gcd_inner(int a, int b) {
155    return b == 0 ? a : gcd_inner(b, a % b);
156  }
157  constexpr int gcd(int a, int b) {
158    return gcd_inner(max(a, b), min(a, b));
159  }
160
161  static_assert(gcd(1749237, 5628959) == 7, "");
162}
163
164namespace FunctionCast {
165  // When folding, we allow functions to be cast to different types. Such
166  // cast functions cannot be called, even if they're constexpr.
167  constexpr int f() { return 1; }
168  typedef double (*DoubleFn)();
169  typedef int (*IntFn)();
170  int a[(int)DoubleFn(f)()]; // expected-error {{variable length array}} expected-warning{{C99 feature}}
171  int b[(int)IntFn(f)()];    // ok
172}
173
174namespace StaticMemberFunction {
175  struct S {
176    static constexpr int k = 42;
177    static constexpr int f(int n) { return n * k + 2; }
178  } s;
179
180  constexpr int n = s.f(19);
181  static_assert(S::f(19) == 800, "");
182  static_assert(s.f(19) == 800, "");
183  static_assert(n == 800, "");
184
185  constexpr int (*sf1)(int) = &S::f;
186  constexpr int (*sf2)(int) = &s.f;
187  constexpr const int *sk = &s.k;
188}
189
190namespace ParameterScopes {
191
192  const int k = 42;
193  constexpr const int &ObscureTheTruth(const int &a) { return a; }
194  constexpr const int &MaybeReturnJunk(bool b, const int a) { // expected-note 2{{declared here}}
195    return ObscureTheTruth(b ? a : k);
196  }
197  static_assert(MaybeReturnJunk(false, 0) == 42, ""); // ok
198  constexpr int a = MaybeReturnJunk(true, 0); // expected-error {{constant expression}} expected-note {{read of variable whose lifetime has ended}}
199
200  constexpr const int MaybeReturnNonstaticRef(bool b, const int a) {
201    return ObscureTheTruth(b ? a : k);
202  }
203  static_assert(MaybeReturnNonstaticRef(false, 0) == 42, ""); // ok
204  constexpr int b = MaybeReturnNonstaticRef(true, 0); // ok
205
206  constexpr int InternalReturnJunk(int n) {
207    return MaybeReturnJunk(true, n); // expected-note {{read of variable whose lifetime has ended}}
208  }
209  constexpr int n3 = InternalReturnJunk(0); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to 'InternalReturnJunk(0)'}}
210
211  constexpr int LToR(int &n) { return n; }
212  constexpr int GrabCallersArgument(bool which, int a, int b) {
213    return LToR(which ? b : a);
214  }
215  static_assert(GrabCallersArgument(false, 1, 2) == 1, "");
216  static_assert(GrabCallersArgument(true, 4, 8) == 8, "");
217
218}
219
220namespace Pointers {
221
222  constexpr int f(int n, const int *a, const int *b, const int *c) {
223    return n == 0 ? 0 : *a + f(n-1, b, c, a);
224  }
225
226  const int x = 1, y = 10, z = 100;
227  static_assert(f(23, &x, &y, &z) == 788, "");
228
229  constexpr int g(int n, int a, int b, int c) {
230    return f(n, &a, &b, &c);
231  }
232  static_assert(g(23, x, y, z) == 788, "");
233
234}
235
236namespace FunctionPointers {
237
238  constexpr int Double(int n) { return 2 * n; }
239  constexpr int Triple(int n) { return 3 * n; }
240  constexpr int Twice(int (*F)(int), int n) { return F(F(n)); }
241  constexpr int Quadruple(int n) { return Twice(Double, n); }
242  constexpr auto Select(int n) -> int (*)(int) {
243    return n == 2 ? &Double : n == 3 ? &Triple : n == 4 ? &Quadruple : 0;
244  }
245  constexpr int Apply(int (*F)(int), int n) { return F(n); } // expected-note {{subexpression}}
246
247  static_assert(1 + Apply(Select(4), 5) + Apply(Select(3), 7) == 42, "");
248
249  constexpr int Invalid = Apply(Select(0), 0); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to 'Apply(0, 0)'}}
250
251}
252
253namespace PointerComparison {
254
255int x, y;
256static_assert(&x == &y, "false"); // expected-error {{false}}
257static_assert(&x != &y, "");
258constexpr bool g1 = &x == &y;
259constexpr bool g2 = &x != &y;
260constexpr bool g3 = &x <= &y; // expected-error {{must be initialized by a constant expression}}
261constexpr bool g4 = &x >= &y; // expected-error {{must be initialized by a constant expression}}
262constexpr bool g5 = &x < &y; // expected-error {{must be initialized by a constant expression}}
263constexpr bool g6 = &x > &y; // expected-error {{must be initialized by a constant expression}}
264
265struct S { int x, y; } s;
266static_assert(&s.x == &s.y, "false"); // expected-error {{false}}
267static_assert(&s.x != &s.y, "");
268static_assert(&s.x <= &s.y, "");
269static_assert(&s.x >= &s.y, "false"); // expected-error {{false}}
270static_assert(&s.x < &s.y, "");
271static_assert(&s.x > &s.y, "false"); // expected-error {{false}}
272
273static_assert(0 == &y, "false"); // expected-error {{false}}
274static_assert(0 != &y, "");
275constexpr bool n3 = 0 <= &y; // expected-error {{must be initialized by a constant expression}}
276constexpr bool n4 = 0 >= &y; // expected-error {{must be initialized by a constant expression}}
277constexpr bool n5 = 0 < &y; // expected-error {{must be initialized by a constant expression}}
278constexpr bool n6 = 0 > &y; // expected-error {{must be initialized by a constant expression}}
279
280static_assert(&x == 0, "false"); // expected-error {{false}}
281static_assert(&x != 0, "");
282constexpr bool n9 = &x <= 0; // expected-error {{must be initialized by a constant expression}}
283constexpr bool n10 = &x >= 0; // expected-error {{must be initialized by a constant expression}}
284constexpr bool n11 = &x < 0; // expected-error {{must be initialized by a constant expression}}
285constexpr bool n12 = &x > 0; // expected-error {{must be initialized by a constant expression}}
286
287static_assert(&x == &x, "");
288static_assert(&x != &x, "false"); // expected-error {{false}}
289static_assert(&x <= &x, "");
290static_assert(&x >= &x, "");
291static_assert(&x < &x, "false"); // expected-error {{false}}
292static_assert(&x > &x, "false"); // expected-error {{false}}
293
294constexpr S* sptr = &s;
295constexpr bool dyncast = sptr == dynamic_cast<S*>(sptr); // expected-error {{constant expression}} expected-note {{dynamic_cast}}
296
297struct U {};
298struct Str {
299  int a : dynamic_cast<S*>(sptr) == dynamic_cast<S*>(sptr); // \
300    expected-warning {{not an integral constant expression}} \
301    expected-note {{dynamic_cast is not allowed in a constant expression}}
302  int b : reinterpret_cast<S*>(sptr) == reinterpret_cast<S*>(sptr); // \
303    expected-warning {{not an integral constant expression}} \
304    expected-note {{reinterpret_cast is not allowed in a constant expression}}
305  int c : (S*)(long)(sptr) == (S*)(long)(sptr); // \
306    expected-warning {{not an integral constant expression}} \
307    expected-note {{cast which performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
308  int d : (S*)(42) == (S*)(42); // \
309    expected-warning {{not an integral constant expression}} \
310    expected-note {{cast which performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
311  int e : (Str*)(sptr) == (Str*)(sptr); // \
312    expected-warning {{not an integral constant expression}} \
313    expected-note {{cast which performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
314  int f : &(U&)(*sptr) == &(U&)(*sptr); // \
315    expected-warning {{not an integral constant expression}} \
316    expected-note {{cast which performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
317  int g : (S*)(void*)(sptr) == sptr; // \
318    expected-warning {{not an integral constant expression}} \
319    expected-note {{cast from 'void *' is not allowed in a constant expression}}
320};
321
322extern char externalvar[];
323constexpr bool constaddress = (void *)externalvar == (void *)0x4000UL; // expected-error {{must be initialized by a constant expression}}
324constexpr bool litaddress = "foo" == "foo"; // expected-error {{must be initialized by a constant expression}} expected-warning {{unspecified}}
325static_assert(0 != "foo", "");
326
327}
328
329namespace MaterializeTemporary {
330
331constexpr int f(const int &r) { return r; }
332constexpr int n = f(1);
333
334constexpr bool same(const int &a, const int &b) { return &a == &b; }
335constexpr bool sameTemporary(const int &n) { return same(n, n); }
336
337static_assert(n, "");
338static_assert(!same(4, 4), "");
339static_assert(same(n, n), "");
340static_assert(sameTemporary(9), "");
341
342}
343
344constexpr int strcmp_ce(const char *p, const char *q) {
345  return (!*p || *p != *q) ? *p - *q : strcmp_ce(p+1, q+1);
346}
347
348namespace StringLiteral {
349
350template<typename Char>
351constexpr int MangleChars(const Char *p) {
352  return *p + 3 * (*p ? MangleChars(p+1) : 0);
353}
354
355static_assert(MangleChars("constexpr!") == 1768383, "");
356static_assert(MangleChars(u8"constexpr!") == 1768383, "");
357static_assert(MangleChars(L"constexpr!") == 1768383, "");
358static_assert(MangleChars(u"constexpr!") == 1768383, "");
359static_assert(MangleChars(U"constexpr!") == 1768383, "");
360
361constexpr char c0 = "nought index"[0];
362constexpr char c1 = "nice index"[10];
363constexpr char c2 = "nasty index"[12]; // expected-error {{must be initialized by a constant expression}} expected-warning {{is past the end}} expected-note {{read of dereferenced one-past-the-end pointer}}
364constexpr char c3 = "negative index"[-1]; // expected-error {{must be initialized by a constant expression}} expected-warning {{is before the beginning}} expected-note {{cannot refer to element -1 of array of 15 elements}}
365constexpr char c4 = ((char*)(int*)"no reinterpret_casts allowed")[14]; // expected-error {{must be initialized by a constant expression}} expected-note {{cast which performs the conversions of a reinterpret_cast}}
366
367constexpr const char *p = "test" + 2;
368static_assert(*p == 's', "");
369
370constexpr const char *max_iter(const char *a, const char *b) {
371  return *a < *b ? b : a;
372}
373constexpr const char *max_element(const char *a, const char *b) {
374  return (a+1 >= b) ? a : max_iter(a, max_element(a+1, b));
375}
376
377constexpr char str[] = "the quick brown fox jumped over the lazy dog";
378constexpr const char *max = max_element(begin(str), end(str));
379static_assert(*max == 'z', "");
380static_assert(max == str + 38, "");
381
382static_assert(strcmp_ce("hello world", "hello world") == 0, "");
383static_assert(strcmp_ce("hello world", "hello clang") > 0, "");
384static_assert(strcmp_ce("constexpr", "test") < 0, "");
385static_assert(strcmp_ce("", " ") < 0, "");
386
387struct S {
388  int n : "foo"[4]; // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer is not allowed in a constant expression}}
389};
390
391struct T {
392  char c[6];
393  constexpr T() : c{"foo"} {}
394};
395constexpr T t;
396
397static_assert(t.c[0] == 'f', "");
398static_assert(t.c[1] == 'o', "");
399static_assert(t.c[2] == 'o', "");
400static_assert(t.c[3] == 0, "");
401static_assert(t.c[4] == 0, "");
402static_assert(t.c[5] == 0, "");
403static_assert(t.c[6] == 0, ""); // expected-error {{constant expression}} expected-note {{one-past-the-end}}
404
405struct U {
406  wchar_t chars[6];
407  int n;
408} constexpr u = { { L"test" }, 0 };
409static_assert(u.chars[2] == L's', "");
410
411struct V {
412  char c[4];
413  constexpr V() : c("hi!") {}
414};
415static_assert(V().c[1] == "i"[0], "");
416
417}
418
419namespace Array {
420
421template<typename Iter>
422constexpr auto Sum(Iter begin, Iter end) -> decltype(+*begin) {
423  return begin == end ? 0 : *begin + Sum(begin+1, end);
424}
425
426constexpr int xs[] = { 1, 2, 3, 4, 5 };
427constexpr int ys[] = { 5, 4, 3, 2, 1 };
428constexpr int sum_xs = Sum(begin(xs), end(xs));
429static_assert(sum_xs == 15, "");
430
431constexpr int ZipFoldR(int (*F)(int x, int y, int c), int n,
432                       const int *xs, const int *ys, int c) {
433  return n ? F(
434               *xs, // expected-note {{read of dereferenced one-past-the-end pointer}}
435               *ys,
436               ZipFoldR(F, n-1, xs+1, ys+1, c)) // \
437      expected-note {{in call to 'ZipFoldR(&SubMul, 2, &xs[4], &ys[4], 1)'}} \
438      expected-note {{in call to 'ZipFoldR(&SubMul, 1, &xs[5], &ys[5], 1)'}}
439           : c;
440}
441constexpr int MulAdd(int x, int y, int c) { return x * y + c; }
442constexpr int InnerProduct = ZipFoldR(MulAdd, 5, xs, ys, 0);
443static_assert(InnerProduct == 35, "");
444
445constexpr int SubMul(int x, int y, int c) { return (x - y) * c; }
446constexpr int DiffProd = ZipFoldR(SubMul, 2, xs+3, ys+3, 1);
447static_assert(DiffProd == 8, "");
448static_assert(ZipFoldR(SubMul, 3, xs+3, ys+3, 1), ""); // \
449      expected-error {{constant expression}} \
450      expected-note {{in call to 'ZipFoldR(&SubMul, 3, &xs[3], &ys[3], 1)'}}
451
452constexpr const int *p = xs + 3;
453constexpr int xs4 = p[1]; // ok
454constexpr int xs5 = p[2]; // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
455constexpr int xs6 = p[3]; // expected-error {{constant expression}} expected-note {{cannot refer to element 6}}
456constexpr int xs0 = p[-3]; // ok
457constexpr int xs_1 = p[-4]; // expected-error {{constant expression}} expected-note {{cannot refer to element -1}}
458
459constexpr int zs[2][2][2][2] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
460static_assert(zs[0][0][0][0] == 1, "");
461static_assert(zs[1][1][1][1] == 16, "");
462static_assert(zs[0][0][0][2] == 3, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
463static_assert((&zs[0][0][0][2])[-1] == 2, "");
464static_assert(**(**(zs + 1) + 1) == 11, "");
465static_assert(*(&(&(*(*&(&zs[2] - 1)[0] + 2 - 2))[2])[-1][-1] + 1) == 11, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element -1 of array of 2 elements in a constant expression}}
466static_assert(*(&(&(*(*&(&zs[2] - 1)[0] + 2 - 2))[2])[-1][2] - 2) == 11, "");
467constexpr int err_zs_1_2_0_0 = zs[1][2][0][0]; // expected-error {{constant expression}} expected-note {{cannot access array element of pointer past the end}}
468
469constexpr int fail(const int &p) {
470  return (&p)[64]; // expected-note {{cannot refer to element 64 of array of 2 elements}}
471}
472static_assert(fail(*(&(&(*(*&(&zs[2] - 1)[0] + 2 - 2))[2])[-1][2] - 2)) == 11, ""); // \
473expected-error {{static_assert expression is not an integral constant expression}} \
474expected-note {{in call to 'fail(zs[1][0][1][0])'}}
475
476constexpr int arr[40] = { 1, 2, 3, [8] = 4 }; // expected-warning {{C99 feature}}
477constexpr int SumNonzero(const int *p) {
478  return *p + (*p ? SumNonzero(p+1) : 0);
479}
480constexpr int CountZero(const int *p, const int *q) {
481  return p == q ? 0 : (*p == 0) + CountZero(p+1, q);
482}
483static_assert(SumNonzero(arr) == 6, "");
484static_assert(CountZero(arr, arr + 40) == 36, "");
485
486struct ArrayElem {
487  constexpr ArrayElem() : n(0) {}
488  int n;
489  constexpr int f() { return n; }
490};
491struct ArrayRVal {
492  constexpr ArrayRVal() {}
493  ArrayElem elems[10];
494};
495static_assert(ArrayRVal().elems[3].f() == 0, "");
496
497}
498
499namespace DependentValues {
500
501struct I { int n; typedef I V[10]; };
502I::V x, y;
503template<bool B> struct S {
504  int k;
505  void f() {
506    I::V &cells = B ? x : y;
507    I &i = cells[k];
508    switch (i.n) {}
509  }
510};
511
512}
513
514namespace Class {
515
516struct A { constexpr A(int a, int b) : k(a + b) {} int k; };
517constexpr int fn(const A &a) { return a.k; }
518static_assert(fn(A(4,5)) == 9, "");
519
520struct B { int n; int m; } constexpr b = { 0, b.n }; // expected-warning {{uninitialized}}
521struct C {
522  constexpr C(C *this_) : m(42), n(this_->m) {} // ok
523  int m, n;
524};
525struct D {
526  C c;
527  constexpr D() : c(&c) {}
528};
529static_assert(D().c.n == 42, "");
530
531struct E {
532  constexpr E() : p(&p) {}
533  void *p;
534};
535constexpr const E &e1 = E(); // expected-error {{constant expression}} expected-note {{reference to temporary is not a constant expression}} expected-note {{temporary created here}}
536// This is a constant expression if we elide the copy constructor call, and
537// is not a constant expression if we don't! But we do, so it is.
538constexpr E e2 = E();
539static_assert(e2.p == &e2.p, "");
540constexpr E e3;
541static_assert(e3.p == &e3.p, "");
542
543extern const class F f;
544struct F {
545  constexpr F() : p(&f.p) {}
546  const void *p;
547};
548constexpr F f;
549
550struct G {
551  struct T {
552    constexpr T(T *p) : u1(), u2(p) {}
553    union U1 {
554      constexpr U1() {}
555      int a, b = 42;
556    } u1;
557    union U2 {
558      constexpr U2(T *p) : c(p->u1.b) {}
559      int c, d;
560    } u2;
561  } t;
562  constexpr G() : t(&t) {}
563} constexpr g;
564
565static_assert(g.t.u1.a == 42, ""); // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
566static_assert(g.t.u1.b == 42, "");
567static_assert(g.t.u2.c == 42, "");
568static_assert(g.t.u2.d == 42, ""); // expected-error {{constant expression}} expected-note {{read of member 'd' of union with active member 'c'}}
569
570struct S {
571  int a, b;
572  const S *p;
573  double d;
574  const char *q;
575
576  constexpr S(int n, const S *p) : a(5), b(n), p(p), d(n), q("hello") {}
577};
578
579S global(43, &global);
580
581static_assert(S(15, &global).b == 15, "");
582
583constexpr bool CheckS(const S &s) {
584  return s.a == 5 && s.b == 27 && s.p == &global && s.d == 27. && s.q[3] == 'l';
585}
586static_assert(CheckS(S(27, &global)), "");
587
588struct Arr {
589  char arr[3];
590  constexpr Arr() : arr{'x', 'y', 'z'} {}
591};
592constexpr int hash(Arr &&a) {
593  return a.arr[0] + a.arr[1] * 0x100 + a.arr[2] * 0x10000;
594}
595constexpr int k = hash(Arr());
596static_assert(k == 0x007a7978, "");
597
598
599struct AggregateInit {
600  const char &c;
601  int n;
602  double d;
603  int arr[5];
604  void *p;
605};
606
607constexpr AggregateInit agg1 = { "hello"[0] };
608
609static_assert(strcmp_ce(&agg1.c, "hello") == 0, "");
610static_assert(agg1.n == 0, "");
611static_assert(agg1.d == 0.0, "");
612static_assert(agg1.arr[-1] == 0, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element -1}}
613static_assert(agg1.arr[0] == 0, "");
614static_assert(agg1.arr[4] == 0, "");
615static_assert(agg1.arr[5] == 0, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end}}
616static_assert(agg1.p == nullptr, "");
617
618namespace SimpleDerivedClass {
619
620struct B {
621  constexpr B(int n) : a(n) {}
622  int a;
623};
624struct D : B {
625  constexpr D(int n) : B(n) {}
626};
627constexpr D d(3);
628static_assert(d.a == 3, "");
629
630}
631
632struct Bottom { constexpr Bottom() {} };
633struct Base : Bottom {
634  constexpr Base(int a = 42, const char *b = "test") : a(a), b(b) {}
635  int a;
636  const char *b;
637};
638struct Base2 : Bottom {
639  constexpr Base2(const int &r) : r(r) {}
640  int q = 123;
641  const int &r;
642};
643struct Derived : Base, Base2 {
644  constexpr Derived() : Base(76), Base2(a) {}
645  int c = r + b[1];
646};
647
648constexpr bool operator==(const Base &a, const Base &b) {
649  return a.a == b.a && strcmp_ce(a.b, b.b) == 0;
650}
651
652constexpr Base base;
653constexpr Base base2(76);
654constexpr Derived derived;
655static_assert(derived.a == 76, "");
656static_assert(derived.b[2] == 's', "");
657static_assert(derived.c == 76 + 'e', "");
658static_assert(derived.q == 123, "");
659static_assert(derived.r == 76, "");
660static_assert(&derived.r == &derived.a, "");
661
662static_assert(!(derived == base), "");
663static_assert(derived == base2, "");
664
665constexpr Bottom &bot1 = (Base&)derived;
666constexpr Bottom &bot2 = (Base2&)derived;
667static_assert(&bot1 != &bot2, "");
668
669constexpr Bottom *pb1 = (Base*)&derived;
670constexpr Bottom *pb2 = (Base2*)&derived;
671static_assert(&pb1 != &pb2, "");
672static_assert(pb1 == &bot1, "");
673static_assert(pb2 == &bot2, "");
674
675constexpr Base2 &fail = (Base2&)bot1; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base2'}}
676constexpr Base &fail2 = (Base&)*pb2; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base'}}
677constexpr Base2 &ok2 = (Base2&)bot2;
678static_assert(&ok2 == &derived, "");
679
680constexpr Base2 *pfail = (Base2*)pb1; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base2'}}
681constexpr Base *pfail2 = (Base*)&bot2; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base'}}
682constexpr Base2 *pok2 = (Base2*)pb2;
683static_assert(pok2 == &derived, "");
684static_assert(&ok2 == pok2, "");
685static_assert((Base2*)(Derived*)(Base*)pb1 == pok2, "");
686static_assert((Derived*)(Base*)pb1 == (Derived*)pok2, "");
687
688constexpr Base *nullB = 42 - 6 * 7;
689static_assert((Bottom*)nullB == 0, "");
690static_assert((Derived*)nullB == 0, "");
691static_assert((void*)(Bottom*)nullB == (void*)(Derived*)nullB, "");
692
693namespace ConversionOperators {
694
695struct T {
696  constexpr T(int n) : k(5*n - 3) {}
697  constexpr operator int() { return k; }
698  int k;
699};
700
701struct S {
702  constexpr S(int n) : k(2*n + 1) {}
703  constexpr operator int() { return k; }
704  constexpr operator T() { return T(k); }
705  int k;
706};
707
708constexpr bool check(T a, T b) { return a == b.k; }
709
710static_assert(S(5) == 11, "");
711static_assert(check(S(5), 11), "");
712
713}
714
715}
716
717namespace Temporaries {
718
719struct S {
720  constexpr S() {}
721  constexpr int f();
722};
723struct T : S {
724  constexpr T(int n) : S(), n(n) {}
725  int n;
726};
727constexpr int S::f() {
728  // 'this' must be the postfix-expression in a class member access expression,
729  // so we can't just use
730  //   return static_cast<T*>(this)->n;
731  return this->*(int(S::*))&T::n;
732}
733// The T temporary is implicitly cast to an S subobject, but we can recover the
734// T full-object via a base-to-derived cast, or a derived-to-base-casted member
735// pointer.
736static_assert(T(3).f() == 3, "");
737
738constexpr int f(const S &s) {
739  return static_cast<const T&>(s).n;
740}
741constexpr int n = f(T(5));
742static_assert(f(T(5)) == 5, "");
743
744constexpr bool b(int n) { return &n; }
745static_assert(b(0), "");
746
747}
748
749namespace Union {
750
751union U {
752  int a;
753  int b;
754};
755
756constexpr U u[4] = { { .a = 0 }, { .b = 1 }, { .a = 2 }, { .b = 3 } }; // expected-warning 4{{C99 feature}}
757static_assert(u[0].a == 0, "");
758static_assert(u[0].b, ""); // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
759static_assert(u[1].b == 1, "");
760static_assert((&u[1].b)[1] == 2, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
761static_assert(*(&(u[1].b) + 1 + 1) == 3, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element 2 of non-array object}}
762static_assert((&(u[1]) + 1 + 1)->b == 3, "");
763
764constexpr U v = {};
765static_assert(v.a == 0, "");
766
767union Empty {};
768constexpr Empty e = {};
769
770// Make sure we handle trivial copy constructors for unions.
771constexpr U x = {42};
772constexpr U y = x;
773static_assert(y.a == 42, "");
774static_assert(y.b == 42, ""); // expected-error {{constant expression}} expected-note {{'b' of union with active member 'a'}}
775
776}
777
778namespace MemberPointer {
779  struct A {
780    constexpr A(int n) : n(n) {}
781    int n;
782    constexpr int f() { return n + 3; }
783  };
784  constexpr A a(7);
785  static_assert(A(5).*&A::n == 5, "");
786  static_assert((&a)->*&A::n == 7, "");
787  static_assert((A(8).*&A::f)() == 11, "");
788  static_assert(((&a)->*&A::f)() == 10, "");
789
790  struct B : A {
791    constexpr B(int n, int m) : A(n), m(m) {}
792    int m;
793    constexpr int g() { return n + m + 1; }
794  };
795  constexpr B b(9, 13);
796  static_assert(B(4, 11).*&A::n == 4, "");
797  static_assert(B(4, 11).*&B::m == 11, "");
798  static_assert(B(4, 11).*(int(A::*))&B::m == 11, "");
799  static_assert((&b)->*&A::n == 9, "");
800  static_assert((&b)->*&B::m == 13, "");
801  static_assert((&b)->*(int(A::*))&B::m == 13, "");
802  static_assert((B(4, 11).*&A::f)() == 7, "");
803  static_assert((B(4, 11).*&B::g)() == 16, "");
804  static_assert((B(4, 11).*(int(A::*)()const)&B::g)() == 16, "");
805  static_assert(((&b)->*&A::f)() == 12, "");
806  static_assert(((&b)->*&B::g)() == 23, "");
807  static_assert(((&b)->*(int(A::*)()const)&B::g)() == 23, "");
808
809  struct S {
810    constexpr S(int m, int n, int (S::*pf)() const, int S::*pn) :
811      m(m), n(n), pf(pf), pn(pn) {}
812    constexpr S() : m(), n(), pf(&S::f), pn(&S::n) {}
813
814    constexpr int f() { return this->*pn; }
815    virtual int g() const;
816
817    int m, n;
818    int (S::*pf)() const;
819    int S::*pn;
820  };
821
822  constexpr int S::*pm = &S::m;
823  constexpr int S::*pn = &S::n;
824  constexpr int (S::*pf)() const = &S::f;
825  constexpr int (S::*pg)() const = &S::g;
826
827  constexpr S s(2, 5, &S::f, &S::m);
828
829  static_assert((s.*&S::f)() == 2, "");
830  static_assert((s.*s.pf)() == 2, "");
831
832  static_assert(pf == &S::f, "");
833  static_assert(pf == s.*&S::pf, "");
834  static_assert(pm == &S::m, "");
835  static_assert(pm != pn, "");
836  static_assert(s.pn != pn, "");
837  static_assert(s.pn == pm, "");
838  static_assert(pg != nullptr, "");
839  static_assert(pf != nullptr, "");
840  static_assert((int S::*)nullptr == nullptr, "");
841  static_assert(pg == pg, ""); // expected-error {{constant expression}} expected-note {{comparison of pointer to virtual member function 'g' has unspecified value}}
842  static_assert(pf != pg, ""); // expected-error {{constant expression}} expected-note {{comparison of pointer to virtual member function 'g' has unspecified value}}
843
844  template<int n> struct T : T<n-1> {};
845  template<> struct T<0> { int n; };
846  template<> struct T<30> : T<29> { int m; };
847
848  T<17> t17;
849  T<30> t30;
850
851  constexpr int (T<10>::*deepn) = &T<0>::n;
852  static_assert(&(t17.*deepn) == &t17.n, "");
853  static_assert(deepn == &T<2>::n, "");
854
855  constexpr int (T<15>::*deepm) = (int(T<10>::*))&T<30>::m;
856  constexpr int *pbad = &(t17.*deepm); // expected-error {{constant expression}}
857  static_assert(&(t30.*deepm) == &t30.m, "");
858  static_assert(deepm == &T<50>::m, "");
859  static_assert(deepm != deepn, "");
860
861  constexpr T<5> *p17_5 = &t17;
862  constexpr T<13> *p17_13 = (T<13>*)p17_5;
863  constexpr T<23> *p17_23 = (T<23>*)p17_13; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'T<17>' to type 'T<23>'}}
864  static_assert(&(p17_5->*(int(T<3>::*))deepn) == &t17.n, "");
865  static_assert(&(p17_13->*deepn) == &t17.n, "");
866  constexpr int *pbad2 = &(p17_13->*(int(T<9>::*))deepm); // expected-error {{constant expression}}
867
868  constexpr T<5> *p30_5 = &t30;
869  constexpr T<23> *p30_23 = (T<23>*)p30_5;
870  constexpr T<13> *p30_13 = p30_23;
871  static_assert(&(p30_5->*(int(T<3>::*))deepn) == &t30.n, "");
872  static_assert(&(p30_13->*deepn) == &t30.n, "");
873  static_assert(&(p30_23->*deepn) == &t30.n, "");
874  static_assert(&(p30_5->*(int(T<2>::*))deepm) == &t30.m, "");
875  static_assert(&(((T<17>*)p30_13)->*deepm) == &t30.m, "");
876  static_assert(&(p30_23->*deepm) == &t30.m, "");
877
878  struct Base { int n; };
879  template<int N> struct Mid : Base {};
880  struct Derived : Mid<0>, Mid<1> {};
881  static_assert(&Mid<0>::n == &Mid<1>::n, "");
882  static_assert((int Derived::*)(int Mid<0>::*)&Mid<0>::n !=
883                (int Derived::*)(int Mid<1>::*)&Mid<1>::n, "");
884  static_assert(&Mid<0>::n == (int Mid<0>::*)&Base::n, "");
885}
886
887namespace ArrayBaseDerived {
888
889  struct Base {
890    constexpr Base() {}
891    int n = 0;
892  };
893  struct Derived : Base {
894    constexpr Derived() {}
895    constexpr const int *f() { return &n; }
896  };
897
898  constexpr Derived a[10];
899  constexpr Derived *pd3 = const_cast<Derived*>(&a[3]);
900  constexpr Base *pb3 = const_cast<Derived*>(&a[3]);
901  static_assert(pb3 == pd3, "");
902
903  // pb3 does not point to an array element.
904  constexpr Base *pb4 = pb3 + 1; // ok, one-past-the-end pointer.
905  constexpr int pb4n = pb4->n; // expected-error {{constant expression}} expected-note {{cannot access field of pointer past the end}}
906  constexpr Base *err_pb5 = pb3 + 2; // expected-error {{constant expression}} expected-note {{cannot refer to element 2}} expected-note {{here}}
907  constexpr int err_pb5n = err_pb5->n; // expected-error {{constant expression}} expected-note {{initializer of 'err_pb5' is not a constant expression}}
908  constexpr Base *err_pb2 = pb3 - 1; // expected-error {{constant expression}} expected-note {{cannot refer to element -1}} expected-note {{here}}
909  constexpr int err_pb2n = err_pb2->n; // expected-error {{constant expression}} expected-note {{initializer of 'err_pb2'}}
910  constexpr Base *pb3a = pb4 - 1;
911
912  // pb4 does not point to a Derived.
913  constexpr Derived *err_pd4 = (Derived*)pb4; // expected-error {{constant expression}} expected-note {{cannot access derived class of pointer past the end}}
914  constexpr Derived *pd3a = (Derived*)pb3a;
915  constexpr int pd3n = pd3a->n;
916
917  // pd3a still points to the Derived array.
918  constexpr Derived *pd6 = pd3a + 3;
919  static_assert(pd6 == &a[6], "");
920  constexpr Derived *pd9 = pd6 + 3;
921  constexpr Derived *pd10 = pd6 + 4;
922  constexpr int pd9n = pd9->n; // ok
923  constexpr int err_pd10n = pd10->n; // expected-error {{constant expression}} expected-note {{cannot access base class of pointer past the end}}
924  constexpr int pd0n = pd10[-10].n;
925  constexpr int err_pdminus1n = pd10[-11].n; // expected-error {{constant expression}} expected-note {{cannot refer to element -1 of}}
926
927  constexpr Base *pb9 = pd9;
928  constexpr const int *(Base::*pfb)() const =
929      static_cast<const int *(Base::*)() const>(&Derived::f);
930  static_assert((pb9->*pfb)() == &a[9].n, "");
931}
932
933namespace Complex {
934
935class complex {
936  int re, im;
937public:
938  constexpr complex(int re = 0, int im = 0) : re(re), im(im) {}
939  constexpr complex(const complex &o) : re(o.re), im(o.im) {}
940  constexpr complex operator-() const { return complex(-re, -im); }
941  friend constexpr complex operator+(const complex &l, const complex &r) {
942    return complex(l.re + r.re, l.im + r.im);
943  }
944  friend constexpr complex operator-(const complex &l, const complex &r) {
945    return l + -r;
946  }
947  friend constexpr complex operator*(const complex &l, const complex &r) {
948    return complex(l.re * r.re - l.im * r.im, l.re * r.im + l.im * r.re);
949  }
950  friend constexpr bool operator==(const complex &l, const complex &r) {
951    return l.re == r.re && l.im == r.im;
952  }
953  constexpr bool operator!=(const complex &r) const {
954    return re != r.re || im != r.im;
955  }
956  constexpr int real() const { return re; }
957  constexpr int imag() const { return im; }
958};
959
960constexpr complex i = complex(0, 1);
961constexpr complex k = (3 + 4*i) * (6 - 4*i);
962static_assert(complex(1,0).real() == 1, "");
963static_assert(complex(1,0).imag() == 0, "");
964static_assert(((complex)1).imag() == 0, "");
965static_assert(k.real() == 34, "");
966static_assert(k.imag() == 12, "");
967static_assert(k - 34 == 12*i, "");
968static_assert((complex)1 == complex(1), "");
969static_assert((complex)1 != complex(0, 1), "");
970static_assert(complex(1) == complex(1), "");
971static_assert(complex(1) != complex(0, 1), "");
972constexpr complex makeComplex(int re, int im) { return complex(re, im); }
973static_assert(makeComplex(1,0) == complex(1), "");
974static_assert(makeComplex(1,0) != complex(0, 1), "");
975
976class complex_wrap : public complex {
977public:
978  constexpr complex_wrap(int re, int im = 0) : complex(re, im) {}
979  constexpr complex_wrap(const complex_wrap &o) : complex(o) {}
980};
981
982static_assert((complex_wrap)1 == complex(1), "");
983static_assert((complex)1 != complex_wrap(0, 1), "");
984static_assert(complex(1) == complex_wrap(1), "");
985static_assert(complex_wrap(1) != complex(0, 1), "");
986constexpr complex_wrap makeComplexWrap(int re, int im) {
987  return complex_wrap(re, im);
988}
989static_assert(makeComplexWrap(1,0) == complex(1), "");
990static_assert(makeComplexWrap(1,0) != complex(0, 1), "");
991
992}
993
994namespace PR11595 {
995  struct A { constexpr bool operator==(int x) { return true; } };
996  struct B { B(); A& x; };
997  static_assert(B().x == 3, "");  // expected-error {{constant expression}} expected-note {{non-literal type 'PR11595::B' cannot be used in a constant expression}}
998
999  constexpr bool f(int k) { // expected-error {{constexpr function never produces a constant expression}}
1000    return B().x == k; // expected-note {{non-literal type 'PR11595::B' cannot be used in a constant expression}}
1001  }
1002}
1003
1004namespace ExprWithCleanups {
1005  struct A { A(); ~A(); int get(); };
1006  constexpr int get(bool FromA) { return FromA ? A().get() : 1; }
1007  constexpr int n = get(false);
1008}
1009
1010namespace Volatile {
1011
1012volatile constexpr int n1 = 0; // expected-note {{here}}
1013volatile const int n2 = 0; // expected-note {{here}}
1014int n3 = 37; // expected-note {{declared here}}
1015
1016constexpr int m1 = n1; // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}}
1017constexpr int m2 = n2; // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}}
1018constexpr int m1b = const_cast<const int&>(n1); // expected-error {{constant expression}} expected-note {{read of volatile object 'n1'}}
1019constexpr int m2b = const_cast<const int&>(n2); // expected-error {{constant expression}} expected-note {{read of volatile object 'n2'}}
1020
1021struct T { int n; };
1022const T t = { 42 }; // expected-note {{declared here}}
1023
1024constexpr int f(volatile int &&r) {
1025  return r; // expected-note {{read of volatile-qualified type 'volatile int'}}
1026}
1027constexpr int g(volatile int &&r) {
1028  return const_cast<int&>(r); // expected-note {{read of volatile temporary is not allowed in a constant expression}}
1029}
1030struct S {
1031  int j : f(0); // expected-error {{constant expression}} expected-note {{in call to 'f(0)'}}
1032  int k : g(0); // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'g(0)'}}
1033  int l : n3; // expected-error {{constant expression}} expected-note {{read of non-const variable}}
1034  int m : t.n; // expected-error {{constant expression}} expected-note {{read of non-constexpr variable}}
1035};
1036
1037}
1038
1039namespace ExternConstexpr {
1040  extern constexpr int n = 0;
1041  extern constexpr int m; // expected-error {{constexpr variable declaration must be a definition}}
1042  void f() {
1043    extern constexpr int i; // expected-error {{constexpr variable declaration must be a definition}}
1044    constexpr int j = 0;
1045    constexpr int k; // expected-error {{default initialization of an object of const type}}
1046  }
1047}
1048
1049namespace ComplexConstexpr {
1050  constexpr _Complex float test1 = {};
1051  constexpr _Complex float test2 = {1};
1052  constexpr _Complex double test3 = {1,2};
1053  constexpr _Complex int test4 = {4};
1054  constexpr _Complex int test5 = 4;
1055  constexpr _Complex int test6 = {5,6};
1056  typedef _Complex float fcomplex;
1057  constexpr fcomplex test7 = fcomplex();
1058
1059  constexpr const double &t2r = __real test3;
1060  constexpr const double &t2i = __imag test3;
1061  static_assert(&t2r + 1 == &t2i, "");
1062  static_assert(t2r == 1.0, "");
1063  static_assert(t2i == 2.0, "");
1064  constexpr const double *t2p = &t2r;
1065  static_assert(t2p[-1] == 0.0, ""); // expected-error {{constant expr}} expected-note {{cannot refer to element -1 of array of 2 elements}}
1066  static_assert(t2p[0] == 1.0, "");
1067  static_assert(t2p[1] == 2.0, "");
1068  static_assert(t2p[2] == 0.0, ""); // expected-error {{constant expr}} expected-note {{one-past-the-end pointer}}
1069  static_assert(t2p[3] == 0.0, ""); // expected-error {{constant expr}} expected-note {{cannot refer to element 3 of array of 2 elements}}
1070  constexpr _Complex float *p = 0;
1071  constexpr float pr = __real *p; // expected-error {{constant expr}} expected-note {{cannot access real component of null}}
1072  constexpr float pi = __imag *p; // expected-error {{constant expr}} expected-note {{cannot access imaginary component of null}}
1073  constexpr const _Complex double *q = &test3 + 1;
1074  constexpr double qr = __real *q; // expected-error {{constant expr}} expected-note {{cannot access real component of pointer past the end}}
1075  constexpr double qi = __imag *q; // expected-error {{constant expr}} expected-note {{cannot access imaginary component of pointer past the end}}
1076
1077  static_assert(__real test6 == 5, "");
1078  static_assert(__imag test6 == 6, "");
1079  static_assert(&__imag test6 == &__real test6 + 1, "");
1080}
1081
1082namespace InstantiateCaseStmt {
1083  template<int x> constexpr int f() { return x; }
1084  template<int x> int g(int c) { switch(c) { case f<x>(): return 1; } return 0; }
1085  int gg(int c) { return g<4>(c); }
1086}
1087
1088namespace ConvertedConstantExpr {
1089  extern int &m;
1090  extern int &n;
1091
1092  constexpr int k = 4;
1093  int &m = const_cast<int&>(k);
1094
1095  // If we have nothing more interesting to say, ensure we don't produce a
1096  // useless note and instead just point to the non-constant subexpression.
1097  enum class E {
1098    em = m,
1099    en = n, // expected-error {{not a constant expression}}
1100    eo = (m +
1101          n // expected-error {{not a constant expression}}
1102          ),
1103    eq = reinterpret_cast<int>((int*)0) // expected-error {{not a constant expression}} expected-note {{reinterpret_cast}}
1104  };
1105}
1106
1107namespace IndirectField {
1108  struct S {
1109    struct { // expected-warning {{GNU extension}}
1110      union {
1111        struct { // expected-warning {{GNU extension}}
1112          int a;
1113          int b;
1114        };
1115        int c;
1116      };
1117      int d;
1118    };
1119    union {
1120      int e;
1121      int f;
1122    };
1123    constexpr S(int a, int b, int d, int e) : a(a), b(b), d(d), e(e) {}
1124    constexpr S(int c, int d, int f) : c(c), d(d), f(f) {}
1125  };
1126
1127  constexpr S s1(1, 2, 3, 4);
1128  constexpr S s2(5, 6, 7);
1129
1130  // FIXME: The diagnostics here do a very poor job of explaining which unnamed
1131  // member is active and which is requested.
1132  static_assert(s1.a == 1, "");
1133  static_assert(s1.b == 2, "");
1134  static_assert(s1.c == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}}
1135  static_assert(s1.d == 3, "");
1136  static_assert(s1.e == 4, "");
1137  static_assert(s1.f == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}}
1138
1139  static_assert(s2.a == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}}
1140  static_assert(s2.b == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}}
1141  static_assert(s2.c == 5, "");
1142  static_assert(s2.d == 6, "");
1143  static_assert(s2.e == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}}
1144  static_assert(s2.f == 7, "");
1145}
1146
1147// DR1405: don't allow reading mutable members in constant expressions.
1148namespace MutableMembers {
1149  struct MM {
1150    mutable int n; // expected-note 3{{declared here}}
1151  } constexpr mm = { 4 };
1152  constexpr int mmn = mm.n; // expected-error {{constant expression}} expected-note {{read of mutable member 'n' is not allowed in a constant expression}}
1153  int x = (mm.n = 1, 3);
1154  constexpr int mmn2 = mm.n; // expected-error {{constant expression}} expected-note {{read of mutable member 'n' is not allowed in a constant expression}}
1155
1156  // Here's one reason why allowing this would be a disaster...
1157  template<int n> struct Id { int k = n; };
1158  int f() {
1159    constexpr MM m = { 0 };
1160    ++m.n;
1161    return Id<m.n>().k; // expected-error {{not a constant expression}} expected-note {{read of mutable member 'n' is not allowed in a constant expression}}
1162  }
1163
1164  struct A { int n; };
1165  struct B { mutable A a; }; // expected-note {{here}}
1166  struct C { B b; };
1167  constexpr C c[3] = {};
1168  constexpr int k = c[1].b.a.n; // expected-error {{constant expression}} expected-note {{mutable}}
1169}
1170
1171namespace Fold {
1172
1173  // This macro forces its argument to be constant-folded, even if it's not
1174  // otherwise a constant expression.
1175  #define fold(x) (__builtin_constant_p(x) ? (x) : (x))
1176
1177  constexpr int n = (int)(char*)123; // expected-error {{constant expression}} expected-note {{reinterpret_cast}}
1178  constexpr int m = fold((int)(char*)123); // ok
1179  static_assert(m == 123, "");
1180
1181  #undef fold
1182
1183}
1184
1185namespace DR1454 {
1186
1187constexpr const int &f(const int &n) { return n; }
1188constexpr int k1 = f(0); // ok
1189
1190struct Wrap {
1191  const int &value;
1192};
1193constexpr const Wrap &g(const Wrap &w) { return w; }
1194constexpr int k2 = g({0}).value; // ok
1195
1196constexpr const int &i = 0; // expected-error {{constant expression}} expected-note {{temporary}} expected-note 2{{here}}
1197constexpr const int j = i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
1198
1199}
1200
1201namespace RecursiveOpaqueExpr {
1202  template<typename Iter>
1203  constexpr auto LastNonzero(Iter p, Iter q) -> decltype(+*p) {
1204    return p != q ? (LastNonzero(p+1, q) ?: *p) : 0; // expected-warning {{GNU}}
1205  }
1206
1207  constexpr int arr1[] = { 1, 0, 0, 3, 0, 2, 0, 4, 0, 0 };
1208  static_assert(LastNonzero(begin(arr1), end(arr1)) == 4, "");
1209
1210  constexpr int arr2[] = { 1, 0, 0, 3, 0, 2, 0, 4, 0, 5 };
1211  static_assert(LastNonzero(begin(arr2), end(arr2)) == 5, "");
1212}
1213
1214namespace VLASizeof {
1215
1216  void f(int k) {
1217    int arr[k]; // expected-warning {{C99}}
1218    constexpr int n = 1 +
1219        sizeof(arr) // expected-error {{constant expression}}
1220        * 3;
1221  }
1222}
1223
1224namespace CompoundLiteral {
1225  // FIXME:
1226  // We don't model the semantics of this correctly: the compound literal is
1227  // represented as a prvalue in the AST, but actually behaves like an lvalue.
1228  // We treat the compound literal as a temporary and refuse to produce a
1229  // pointer to it. This is OK: we're not required to treat this as a constant
1230  // in C++, and in C we model compound literals as lvalues.
1231  constexpr int *p = (int*)(int[1]){0}; // expected-warning {{C99}} expected-error {{constant expression}} expected-note 2{{temporary}}
1232}
1233