1// RUN: %clang_cc1 -std=c++1y -verify %s -fcxx-exceptions -triple=x86_64-linux-gnu
2
3struct S {
4  // dummy ctor to make this a literal type
5  constexpr S(int);
6
7  S();
8
9  int arr[10];
10
11  constexpr int &get(int n) { return arr[n]; }
12  constexpr const int &get(int n) const { return arr[n]; }
13};
14
15S s = S();
16const S &sr = s;
17static_assert(&s.get(4) - &sr.get(2) == 2, "");
18
19// Compound-statements can be used in constexpr functions.
20constexpr int e() {{{{}} return 5; }}
21static_assert(e() == 5, "");
22
23// Types can be defined in constexpr functions.
24constexpr int f() {
25  enum E { e1, e2, e3 };
26
27  struct S {
28    constexpr S(E e) : e(e) {}
29    constexpr int get() { return e; }
30    E e;
31  };
32
33  return S(e2).get();
34}
35static_assert(f() == 1, "");
36
37// Variables can be declared in constexpr functions.
38constexpr int g(int k) {
39  const int n = 9;
40  int k2 = k * k;
41  int k3 = k2 * k;
42  return 3 * k3 + 5 * k2 + n * k - 20;
43}
44static_assert(g(2) == 42, "");
45constexpr int h(int n) {
46  static const int m = n; // expected-error {{static variable not permitted in a constexpr function}}
47  return m;
48}
49constexpr int i(int n) {
50  thread_local const int m = n; // expected-error {{thread_local variable not permitted in a constexpr function}}
51  return m;
52}
53
54// if-statements can be used in constexpr functions.
55constexpr int j(int k) {
56  if (k == 5)
57    return 1;
58  if (k == 1)
59    return 5;
60  else {
61    if (int n = 2 * k - 4) {
62      return n + 1;
63      return 2;
64    }
65  }
66} // expected-note 2{{control reached end of constexpr function}}
67static_assert(j(0) == -3, "");
68static_assert(j(1) == 5, "");
69static_assert(j(2), ""); // expected-error {{constant expression}} expected-note {{in call to 'j(2)'}}
70static_assert(j(3) == 3, "");
71static_assert(j(4) == 5, "");
72static_assert(j(5) == 1, "");
73
74// There can be 0 return-statements.
75constexpr void k() {
76}
77
78// If the return type is not 'void', no return statements => never a constant
79// expression, so still diagnose that case.
80[[noreturn]] constexpr int fn() { // expected-error {{no return statement in constexpr function}}
81  fn();
82}
83
84// We evaluate the body of a constexpr constructor, to check for side-effects.
85struct U {
86  constexpr U(int n) {
87    if (j(n)) {} // expected-note {{in call to 'j(2)'}}
88  }
89};
90constexpr U u1{1};
91constexpr U u2{2}; // expected-error {{constant expression}} expected-note {{in call to 'U(2)'}}
92
93// We allow expression-statements.
94constexpr int l(bool b) {
95  if (b)
96    throw "invalid value for b!"; // expected-note {{subexpression not valid}}
97  return 5;
98}
99static_assert(l(false) == 5, "");
100static_assert(l(true), ""); // expected-error {{constant expression}} expected-note {{in call to 'l(true)'}}
101
102// Potential constant expression checking is still applied where possible.
103constexpr int htonl(int x) { // expected-error {{never produces a constant expression}}
104  typedef unsigned char uchar;
105  uchar arr[4] = { uchar(x >> 24), uchar(x >> 16), uchar(x >> 8), uchar(x) };
106  return *reinterpret_cast<int*>(arr); // expected-note {{reinterpret_cast is not allowed in a constant expression}}
107}
108
109constexpr int maybe_htonl(bool isBigEndian, int x) {
110  if (isBigEndian)
111    return x;
112
113  typedef unsigned char uchar;
114  uchar arr[4] = { uchar(x >> 24), uchar(x >> 16), uchar(x >> 8), uchar(x) };
115  return *reinterpret_cast<int*>(arr); // expected-note {{reinterpret_cast is not allowed in a constant expression}}
116}
117
118constexpr int swapped = maybe_htonl(false, 123); // expected-error {{constant expression}} expected-note {{in call}}
119
120namespace NS {
121  constexpr int n = 0;
122}
123constexpr int namespace_alias() {
124  namespace N = NS;
125  return N::n;
126}
127
128namespace assign {
129  constexpr int a = 0;
130  const int b = 0;
131  int c = 0; // expected-note {{here}}
132
133  constexpr void set(const int &a, int b) {
134    const_cast<int&>(a) = b; // expected-note 3{{constant expression cannot modify an object that is visible outside that expression}}
135  }
136  constexpr int wrap(int a, int b) {
137    set(a, b);
138    return a;
139  }
140
141  static_assert((set(a, 1), a) == 1, ""); // expected-error {{constant expression}} expected-note {{in call to 'set(a, 1)'}}
142  static_assert((set(b, 1), b) == 1, ""); // expected-error {{constant expression}} expected-note {{in call to 'set(b, 1)'}}
143  static_assert((set(c, 1), c) == 1, ""); // expected-error {{constant expression}} expected-note {{in call to 'set(c, 1)'}}
144
145  static_assert(wrap(a, 1) == 1, "");
146  static_assert(wrap(b, 1) == 1, "");
147  static_assert(wrap(c, 1) == 1, ""); // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
148}
149
150namespace string_assign {
151  template<typename T>
152  constexpr void swap(T &a, T &b) {
153    T tmp = a;
154    a = b;
155    b = tmp;
156  }
157  template<typename Iterator>
158  constexpr void reverse(Iterator begin, Iterator end) {
159    while (begin != end && begin != --end)
160      swap(*begin++, *end);
161  }
162  template<typename Iterator1, typename Iterator2>
163  constexpr bool equal(Iterator1 a, Iterator1 ae, Iterator2 b, Iterator2 be) {
164    while (a != ae && b != be)
165      if (*a++ != *b++)
166        return false;
167    return a == ae && b == be;
168  }
169  constexpr bool test1(int n) {
170    char stuff[100] = "foobarfoo";
171    const char stuff2[100] = "oofraboof";
172    reverse(stuff, stuff + n); // expected-note {{cannot refer to element 101 of array of 100 elements}}
173    return equal(stuff, stuff + n, stuff2, stuff2 + n);
174  }
175  static_assert(!test1(1), "");
176  static_assert(test1(3), "");
177  static_assert(!test1(6), "");
178  static_assert(test1(9), "");
179  static_assert(!test1(100), "");
180  static_assert(!test1(101), ""); // expected-error {{constant expression}} expected-note {{in call to 'test1(101)'}}
181
182  constexpr void f() { // expected-error{{constexpr function never produces a constant expression}} expected-note@+2{{assignment to dereferenced one-past-the-end pointer is not allowed in a constant expression}}
183    char foo[10] = { "z" }; // expected-note {{here}}
184    foo[10] = 'x'; // expected-warning {{past the end}}
185  }
186}
187
188namespace array_resize {
189  constexpr int do_stuff(int k1, int k2) {
190    int arr[1234] = { 1, 2, 3, 4 };
191    arr[k1] = 5; // expected-note {{past-the-end}} expected-note {{cannot refer to element 1235}} expected-note {{cannot refer to element -1}}
192    return arr[k2];
193  }
194  static_assert(do_stuff(1, 2) == 3, "");
195  static_assert(do_stuff(0, 0) == 5, "");
196  static_assert(do_stuff(1233, 1233) == 5, "");
197  static_assert(do_stuff(1233, 0) == 1, "");
198  static_assert(do_stuff(1234, 0) == 1, ""); // expected-error {{constant expression}} expected-note {{in call}}
199  static_assert(do_stuff(1235, 0) == 1, ""); // expected-error {{constant expression}} expected-note {{in call}}
200  static_assert(do_stuff(-1, 0) == 1, ""); // expected-error {{constant expression}} expected-note {{in call}}
201}
202
203namespace potential_const_expr {
204  constexpr void set(int &n) { n = 1; }
205  constexpr int div_zero_1() { int z = 0; set(z); return 100 / z; } // no error
206  constexpr int div_zero_2() { // expected-error {{never produces a constant expression}}
207    int z = 0;
208    return 100 / (set(z), 0); // expected-note {{division by zero}}
209  }
210  int n; // expected-note {{declared here}}
211  constexpr int ref() { // expected-error {{never produces a constant expression}}
212    int &r = n;
213    return r; // expected-note {{read of non-const variable 'n'}}
214  }
215}
216
217namespace subobject {
218  union A { constexpr A() : y(5) {} int x, y; };
219  struct B { A a; };
220  struct C : B {};
221  union D { constexpr D() : c() {} constexpr D(int n) : n(n) {} C c; int n; };
222  constexpr void f(D &d) {
223    d.c.a.y = 3;
224    // expected-note@-1 {{cannot modify an object that is visible outside}}
225    // expected-note@-2 {{assignment to member 'c' of union with active member 'n'}}
226  }
227  constexpr bool check(D &d) { return d.c.a.y == 3; }
228
229  constexpr bool g() { D d; f(d); return d.c.a.y == 3; }
230  static_assert(g(), "");
231
232  D d;
233  constexpr bool h() { f(d); return check(d); } // expected-note {{in call}}
234  static_assert(h(), ""); // expected-error {{constant expression}} expected-note {{in call}}
235
236  constexpr bool i() { D d(0); f(d); return check(d); } // expected-note {{in call}}
237  static_assert(i(), ""); // expected-error {{constant expression}} expected-note {{in call}}
238
239  constexpr bool j() { D d; d.c.a.x = 3; return check(d); } // expected-note {{assignment to member 'x' of union with active member 'y'}}
240  static_assert(j(), ""); // expected-error {{constant expression}} expected-note {{in call}}
241}
242
243namespace lifetime {
244  constexpr int &&id(int &&n) { return static_cast<int&&>(n); }
245  constexpr int &&dead() { return id(0); } // expected-note {{temporary created here}}
246  constexpr int bad() { int &&n = dead(); n = 1; return n; } // expected-note {{assignment to temporary whose lifetime has ended}}
247  static_assert(bad(), ""); // expected-error {{constant expression}} expected-note {{in call}}
248}
249
250namespace const_modify {
251  constexpr int modify(int &n) { return n = 1; } // expected-note 2 {{modification of object of const-qualified type 'const int'}}
252  constexpr int test1() { int k = 0; return modify(k); }
253  constexpr int test2() { const int k = 0; return modify(const_cast<int&>(k)); } // expected-note 2 {{in call}}
254  static_assert(test1() == 1, "");
255  static_assert(test2() == 1, ""); // expected-error {{constant expression}} expected-note {{in call}}
256  constexpr int i = test2(); // expected-error {{constant expression}} expected-note {{in call}}
257}
258
259namespace null {
260  constexpr int test(int *p) {
261    return *p = 123; // expected-note {{assignment to dereferenced null pointer}}
262  }
263  static_assert(test(0), ""); // expected-error {{constant expression}} expected-note {{in call}}
264}
265
266namespace incdec {
267  template<typename T> constexpr T &ref(T &&r) { return r; }
268  template<typename T> constexpr T postinc(T &&r) { return (r++, r); }
269  template<typename T> constexpr T postdec(T &&r) { return (r--, r); }
270
271  static_assert(++ref(0) == 1, "");
272  static_assert(ref(0)++ == 0, "");
273  static_assert(postinc(0) == 1, "");
274  static_assert(--ref(0) == -1, "");
275  static_assert(ref(0)-- == 0, "");
276  static_assert(postdec(0) == -1, "");
277
278  constexpr int overflow_int_inc_1 = ref(0x7fffffff)++; // expected-error {{constant}} expected-note {{2147483648}}
279  constexpr int overflow_int_inc_1_ok = ref(0x7ffffffe)++;
280  constexpr int overflow_int_inc_2 = ++ref(0x7fffffff); // expected-error {{constant}} expected-note {{2147483648}}
281  constexpr int overflow_int_inc_2_ok = ++ref(0x7ffffffe);
282
283  // inc/dec on short can't overflow because we promote to int first
284  static_assert(++ref<short>(0x7fff) == (int)0xffff8000u, "");
285  static_assert(--ref<short>(0x8000) == 0x7fff, "");
286
287  // inc on bool sets to true
288  static_assert(++ref(false), ""); // expected-warning {{deprecated}}
289  static_assert(++ref(true), ""); // expected-warning {{deprecated}}
290
291  int arr[10];
292  static_assert(++ref(&arr[0]) == &arr[1], "");
293  static_assert(++ref(&arr[9]) == &arr[10], "");
294  static_assert(++ref(&arr[10]) == &arr[11], ""); // expected-error {{constant}} expected-note {{cannot refer to element 11}}
295  static_assert(ref(&arr[0])++ == &arr[0], "");
296  static_assert(ref(&arr[10])++ == &arr[10], ""); // expected-error {{constant}} expected-note {{cannot refer to element 11}}
297  static_assert(postinc(&arr[0]) == &arr[1], "");
298  static_assert(--ref(&arr[10]) == &arr[9], "");
299  static_assert(--ref(&arr[1]) == &arr[0], "");
300  static_assert(--ref(&arr[0]) != &arr[0], ""); // expected-error {{constant}} expected-note {{cannot refer to element -1}}
301  static_assert(ref(&arr[1])-- == &arr[1], "");
302  static_assert(ref(&arr[0])-- == &arr[0], ""); // expected-error {{constant}} expected-note {{cannot refer to element -1}}
303  static_assert(postdec(&arr[1]) == &arr[0], "");
304
305  int x;
306  static_assert(++ref(&x) == &x + 1, "");
307
308  static_assert(++ref(0.0) == 1.0, "");
309  static_assert(ref(0.0)++ == 0.0, "");
310  static_assert(postinc(0.0) == 1.0, "");
311  static_assert(--ref(0.0) == -1.0, "");
312  static_assert(ref(0.0)-- == 0.0, "");
313  static_assert(postdec(0.0) == -1.0, "");
314
315  static_assert(++ref(1e100) == 1e100, "");
316  static_assert(--ref(1e100) == 1e100, "");
317
318  union U {
319    int a, b;
320  };
321  constexpr int f(U u) {
322    return ++u.b; // expected-note {{increment of member 'b' of union with active member 'a'}}
323  }
324  constexpr int wrong_member = f({0}); // expected-error {{constant}} expected-note {{in call to 'f({.a = 0})'}}
325  constexpr int vol = --ref<volatile int>(0); // expected-error {{constant}} expected-note {{decrement of volatile-qualified}}
326
327  constexpr int incr(int k) {
328    int x = k;
329    if (x++ == 100)
330      return x;
331    return incr(x);
332  }
333  static_assert(incr(0) == 101, "");
334}
335
336namespace compound_assign {
337  constexpr bool test_int() {
338    int a = 3;
339    a += 6;
340    if (a != 9) return false;
341    a -= 2;
342    if (a != 7) return false;
343    a *= 3;
344    if (a != 21) return false;
345    if (&(a /= 10) != &a) return false;
346    if (a != 2) return false;
347    a <<= 3;
348    if (a != 16) return false;
349    a %= 6;
350    if (a != 4) return false;
351    a >>= 1;
352    if (a != 2) return false;
353    a ^= 10;
354    if (a != 8) return false;
355    a |= 5;
356    if (a != 13) return false;
357    a &= 14;
358    if (a != 12) return false;
359    return true;
360  }
361  static_assert(test_int(), "");
362
363  constexpr bool test_float() {
364    float f = 123.;
365    f *= 2;
366    if (f != 246.) return false;
367    if ((f -= 0.5) != 245.5) return false;
368    if (f != 245.5) return false;
369    f /= 0.5;
370    if (f != 491.) return false;
371    f += -40;
372    if (f != 451.) return false;
373    return true;
374  }
375  static_assert(test_float(), "");
376
377  constexpr bool test_ptr() {
378    int arr[123] = {};
379    int *p = arr;
380    if ((p += 4) != &arr[4]) return false;
381    if (p != &arr[4]) return false;
382    p += -1;
383    if (p != &arr[3]) return false;
384    if ((p -= -10) != &arr[13]) return false;
385    if (p != &arr[13]) return false;
386    p -= 11;
387    if (p != &arr[2]) return false;
388    return true;
389  }
390  static_assert(test_ptr(), "");
391
392  template<typename T>
393  constexpr bool test_overflow() {
394    T a = 1;
395    while (a != a / 2)
396      a *= 2; // expected-note {{value 2147483648 is outside the range}} expected-note {{ 9223372036854775808 }} expected-note {{floating point arithmetic produces an infinity}}
397    return true;
398  }
399
400  static_assert(test_overflow<int>(), ""); // expected-error {{constant}} expected-note {{call}}
401  static_assert(test_overflow<unsigned>(), ""); // ok, unsigned overflow is defined
402  static_assert(test_overflow<short>(), ""); // ok, short is promoted to int before multiplication
403  static_assert(test_overflow<unsigned short>(), ""); // ok
404  static_assert(test_overflow<unsigned long long>(), ""); // ok
405  static_assert(test_overflow<long long>(), ""); // expected-error {{constant}} expected-note {{call}}
406  static_assert(test_overflow<float>(), ""); // expected-error {{constant}} expected-note {{call}}
407
408  constexpr short test_promotion(short k) {
409    short s = k;
410    s *= s;
411    return s;
412  }
413  static_assert(test_promotion(100) == 10000, "");
414  static_assert(test_promotion(200) == -25536, "");
415  static_assert(test_promotion(256) == 0, "");
416
417  constexpr const char *test_bounds(const char *p, int o) {
418    return p += o; // expected-note {{element 5 of}} expected-note {{element -1 of}} expected-note {{element 1000 of}}
419  }
420  static_assert(test_bounds("foo", 0)[0] == 'f', "");
421  static_assert(test_bounds("foo", 3)[0] == 0, "");
422  static_assert(test_bounds("foo", 4)[-3] == 'o', "");
423  static_assert(test_bounds("foo" + 4, -4)[0] == 'f', "");
424  static_assert(test_bounds("foo", 5) != 0, ""); // expected-error {{constant}} expected-note {{call}}
425  static_assert(test_bounds("foo", -1) != 0, ""); // expected-error {{constant}} expected-note {{call}}
426  static_assert(test_bounds("foo", 1000) != 0, ""); // expected-error {{constant}} expected-note {{call}}
427}
428
429namespace loops {
430  constexpr int fib_loop(int a) {
431    int f_k = 0, f_k_plus_one = 1;
432    for (int k = 1; k != a; ++k) {
433      int f_k_plus_two = f_k + f_k_plus_one;
434      f_k = f_k_plus_one;
435      f_k_plus_one = f_k_plus_two;
436    }
437    return f_k_plus_one;
438  }
439  static_assert(fib_loop(46) == 1836311903, "");
440
441  constexpr bool breaks_work() {
442    int a = 0;
443    for (int n = 0; n != 100; ++n) {
444      ++a;
445      if (a == 5) continue;
446      if ((a % 5) == 0) break;
447    }
448
449    int b = 0;
450    while (b != 17) {
451      ++b;
452      if (b == 6) continue;
453      if ((b % 6) == 0) break;
454    }
455
456    int c = 0;
457    do {
458      ++c;
459      if (c == 7) continue;
460      if ((c % 7) == 0) break;
461    } while (c != 21);
462
463    return a == 10 && b == 12 && c == 14;
464  }
465  static_assert(breaks_work(), "");
466
467  void not_constexpr();
468  constexpr bool no_cont_after_break() {
469    for (;;) {
470      break;
471      not_constexpr();
472    }
473    while (true) {
474      break;
475      not_constexpr();
476    }
477    do {
478      break;
479      not_constexpr();
480    } while (true);
481    return true;
482  }
483  static_assert(no_cont_after_break(), "");
484
485  constexpr bool cond() {
486    for (int a = 1; bool b = a != 3; ++a) {
487      if (!b)
488        return false;
489    }
490    while (bool b = true) {
491      b = false;
492      break;
493    }
494    return true;
495  }
496  static_assert(cond(), "");
497
498  constexpr int range_for() {
499    int arr[] = { 1, 2, 3, 4, 5 };
500    int sum = 0;
501    for (int x : arr)
502      sum += x;
503    return sum;
504  }
505  static_assert(range_for() == 15, "");
506
507  template<int...N> struct ints {};
508  template<typename A, typename B> struct join_ints;
509  template<int...As, int...Bs> struct join_ints<ints<As...>, ints<Bs...>> {
510    using type = ints<As..., sizeof...(As) + Bs...>;
511  };
512  template<unsigned N> struct make_ints {
513    using type = typename join_ints<typename make_ints<N/2>::type, typename make_ints<(N+1)/2>::type>::type;
514  };
515  template<> struct make_ints<0> { using type = ints<>; };
516  template<> struct make_ints<1> { using type = ints<0>; };
517
518  struct ignore { template<typename ...Ts> constexpr ignore(Ts &&...) {} };
519
520  template<typename T, unsigned N> struct array {
521    constexpr array() : arr{} {}
522    template<typename ...X>
523    constexpr array(X ...x) : arr{} {
524      init(typename make_ints<sizeof...(X)>::type{}, x...);
525    }
526    template<int ...I, typename ...X> constexpr void init(ints<I...>, X ...x) {
527      ignore{arr[I] = x ...};
528    }
529    T arr[N];
530    struct iterator {
531      T *p;
532      constexpr explicit iterator(T *p) : p(p) {}
533      constexpr bool operator!=(iterator o) { return p != o.p; }
534      constexpr iterator &operator++() { ++p; return *this; }
535      constexpr T &operator*() { return *p; }
536    };
537    constexpr iterator begin() { return iterator(arr); }
538    constexpr iterator end() { return iterator(arr + N); }
539  };
540
541  constexpr int range_for_2() {
542    array<int, 5> arr { 1, 2, 3, 4, 5 };
543    int sum = 0;
544    for (int k : arr) {
545      sum += k;
546      if (sum > 8) break;
547    }
548    return sum;
549  }
550  static_assert(range_for_2() == 10, "");
551}
552
553namespace assignment_op {
554  struct A {
555    constexpr A() : n(5) {}
556    int n;
557    struct B {
558      int k = 1;
559      union U {
560        constexpr U() : y(4) {}
561        int x;
562        int y;
563      } u;
564    } b;
565  };
566  constexpr bool testA() {
567    A a, b;
568    a.n = 7;
569    a.b.u.y = 5;
570    b = a;
571    return b.n == 7 && b.b.u.y == 5 && b.b.k == 1;
572  }
573  static_assert(testA(), "");
574
575  struct B {
576    bool assigned = false;
577    constexpr B &operator=(const B&) {
578      assigned = true;
579      return *this;
580    }
581  };
582  struct C : B {
583    B b;
584    int n = 5;
585  };
586  constexpr bool testC() {
587    C c, d;
588    c.n = 7;
589    d = c;
590    c.n = 3;
591    return d.n == 7 && d.assigned && d.b.assigned;
592  }
593  static_assert(testC(), "");
594}
595
596namespace switch_stmt {
597  constexpr int f(char k) {
598    bool b = false;
599    int z = 6;
600    switch (k) {
601      return -1;
602    case 0:
603      if (false) {
604      case 1:
605        z = 1;
606        for (; b;) {
607          return 5;
608          while (0)
609            case 2: return 2;
610          case 7: z = 7;
611          do case 6: {
612            return z;
613            if (false)
614              case 3: return 3;
615            case 4: z = 4;
616          } while (1);
617          case 5: b = true;
618          case 9: z = 9;
619        }
620        return z;
621      } else if (false) case 8: z = 8;
622      else if (false) {
623      case 10:
624        z = -10;
625        break;
626      }
627      else z = 0;
628      return z;
629    default:
630      return -1;
631    }
632    return -z;
633  }
634  static_assert(f(0) == 0, "");
635  static_assert(f(1) == 1, "");
636  static_assert(f(2) == 2, "");
637  static_assert(f(3) == 3, "");
638  static_assert(f(4) == 4, "");
639  static_assert(f(5) == 5, "");
640  static_assert(f(6) == 6, "");
641  static_assert(f(7) == 7, "");
642  static_assert(f(8) == 8, "");
643  static_assert(f(9) == 9, "");
644  static_assert(f(10) == 10, "");
645
646  // Check that we can continue an outer loop from within a switch.
647  constexpr bool contin() {
648    for (int n = 0; n != 10; ++n) {
649      switch (n) {
650      case 0:
651        ++n;
652        continue;
653      case 1:
654        return false;
655      case 2:
656        return true;
657      }
658    }
659    return false;
660  }
661  static_assert(contin(), "");
662
663  constexpr bool switch_into_for() {
664    int n = 0;
665    switch (n) {
666      for (; n == 1; ++n) {
667        return n == 1;
668      case 0: ;
669      }
670    }
671    return false;
672  }
673  static_assert(switch_into_for(), "");
674
675  constexpr void duff_copy(char *a, const char *b, int n) {
676    switch ((n - 1) % 8 + 1) {
677      for ( ; n; n = (n - 1) & ~7) {
678      case 8: a[n-8] = b[n-8];
679      case 7: a[n-7] = b[n-7];
680      case 6: a[n-6] = b[n-6];
681      case 5: a[n-5] = b[n-5];
682      case 4: a[n-4] = b[n-4];
683      case 3: a[n-3] = b[n-3];
684      case 2: a[n-2] = b[n-2];
685      case 1: a[n-1] = b[n-1];
686      }
687      case 0: ;
688    }
689  }
690
691  constexpr bool test_copy(const char *str, int n) {
692    char buffer[16] = {};
693    duff_copy(buffer, str, n);
694    for (int i = 0; i != sizeof(buffer); ++i)
695      if (buffer[i] != (i < n ? str[i] : 0))
696        return false;
697    return true;
698  }
699  static_assert(test_copy("foo", 0), "");
700  static_assert(test_copy("foo", 1), "");
701  static_assert(test_copy("foo", 2), "");
702  static_assert(test_copy("hello world", 0), "");
703  static_assert(test_copy("hello world", 7), "");
704  static_assert(test_copy("hello world", 8), "");
705  static_assert(test_copy("hello world", 9), "");
706  static_assert(test_copy("hello world", 10), "");
707  static_assert(test_copy("hello world", 10), "");
708}
709
710namespace deduced_return_type {
711  constexpr auto f() { return 0; }
712  template<typename T> constexpr auto g(T t) { return t; }
713  static_assert(f() == 0, "");
714  static_assert(g(true), "");
715}
716
717namespace modify_temporary_during_construction {
718  struct A { int &&temporary; int x; int y; };
719  constexpr int f(int &r) { r *= 9; return r - 12; }
720  constexpr A a = { 6, f(a.temporary), a.temporary }; // expected-note {{temporary created here}}
721  static_assert(a.x == 42, "");
722  static_assert(a.y == 54, "");
723  constexpr int k = a.temporary++; // expected-error {{constant expression}} expected-note {{outside the expression that created the temporary}}
724}
725
726namespace std {
727  typedef decltype(sizeof(int)) size_t;
728
729  template <class _E>
730  class initializer_list
731  {
732    const _E* __begin_;
733    size_t    __size_;
734
735    constexpr initializer_list(const _E* __b, size_t __s)
736      : __begin_(__b),
737        __size_(__s)
738    {}
739
740  public:
741    typedef _E        value_type;
742    typedef const _E& reference;
743    typedef const _E& const_reference;
744    typedef size_t    size_type;
745
746    typedef const _E* iterator;
747    typedef const _E* const_iterator;
748
749    constexpr initializer_list() : __begin_(nullptr), __size_(0) {}
750
751    constexpr size_t    size()  const {return __size_;}
752    constexpr const _E* begin() const {return __begin_;}
753    constexpr const _E* end()   const {return __begin_ + __size_;}
754  };
755}
756
757namespace InitializerList {
758  constexpr int sum(std::initializer_list<int> ints) {
759    int total = 0;
760    for (int n : ints) total += n;
761    return total;
762  }
763  static_assert(sum({1, 2, 3, 4, 5}) == 15, "");
764}
765
766namespace StmtExpr {
767  constexpr int f(int k) {
768    switch (k) {
769    case 0:
770      return 0;
771
772      ({
773        case 1: // expected-note {{not supported}}
774          return 1;
775      });
776    }
777  }
778  static_assert(f(1) == 1, ""); // expected-error {{constant expression}} expected-note {{in call}}
779
780  constexpr int g() { // expected-error {{never produces a constant}}
781    return ({ int n; n; }); // expected-note {{object of type 'int' is not initialized}}
782  }
783
784  // FIXME: We should handle the void statement expression case.
785  constexpr int h() { // expected-error {{never produces a constant}}
786    ({ if (true) {} }); // expected-note {{not supported}}
787    return 0;
788  }
789}
790
791namespace VirtualFromBase {
792  struct S1 {
793    virtual int f() const;
794  };
795  struct S2 {
796    virtual int f();
797  };
798  template <typename T> struct X : T {
799    constexpr X() {}
800    double d = 0.0;
801    constexpr int f() { return sizeof(T); }
802  };
803
804  // Non-virtual f(), OK.
805  constexpr X<X<S1>> xxs1;
806  constexpr X<S1> *p = const_cast<X<X<S1>>*>(&xxs1);
807  static_assert(p->f() == sizeof(S1), "");
808
809  // Virtual f(), not OK.
810  constexpr X<X<S2>> xxs2;
811  constexpr X<S2> *q = const_cast<X<X<S2>>*>(&xxs2);
812  static_assert(q->f() == sizeof(X<S2>), ""); // expected-error {{constant expression}} expected-note {{virtual function call}}
813}
814
815namespace Lifetime {
816  constexpr int &get(int &&r) { return r; }
817  constexpr int f() {
818    int &r = get(123);
819    return r; // expected-note {{read of object outside its lifetime}}
820  }
821  static_assert(f() == 123, ""); // expected-error {{constant expression}} expected-note {{in call}}
822
823  constexpr int g() {
824    int *p = 0;
825    {
826      int n = 0;
827      p = &n;
828      n = 42;
829    }
830    *p = 123; // expected-note {{assignment to object outside its lifetime}}
831    return *p;
832  }
833  static_assert(g() == 42, ""); // expected-error {{constant expression}} expected-note {{in call}}
834
835  constexpr int h(int n) {
836    int *p[4] = {};
837    int &&r = 1;
838    p[0] = &r;
839    while (int a = 1) {
840      p[1] = &a;
841      for (int b = 1; int c = 1; ) {
842        p[2] = &b, p[3] = &c;
843        break;
844      }
845      break;
846    }
847    *p[n] = 0; // expected-note 3{{assignment to object outside its lifetime}}
848    return *p[n];
849  }
850  static_assert(h(0) == 0, ""); // ok, lifetime-extended
851  static_assert(h(1) == 0, ""); // expected-error {{constant expression}} expected-note {{in call}}
852  static_assert(h(2) == 0, ""); // expected-error {{constant expression}} expected-note {{in call}}
853  static_assert(h(3) == 0, ""); // expected-error {{constant expression}} expected-note {{in call}}
854
855  // FIXME: This function should be treated as non-constant.
856  constexpr void lifetime_versus_loops() {
857    int *p = 0;
858    for (int i = 0; i != 2; ++i) {
859      int *q = p;
860      int n = 0;
861      p = &n;
862      if (i)
863        // This modifies the 'n' from the previous iteration of the loop outside
864        // its lifetime.
865        ++*q;
866    }
867  }
868  static_assert((lifetime_versus_loops(), true), "");
869}
870
871namespace Bitfields {
872  struct A {
873    bool b : 1;
874    int n : 4;
875    unsigned u : 5;
876  };
877  constexpr bool test() {
878    A a {};
879    a.b += 2;
880    --a.n;
881    --a.u;
882    a.n = -a.n * 3;
883    return a.b == false && a.n == 3 && a.u == 31;
884  }
885  static_assert(test(), "");
886}
887
888namespace PR17615 {
889  struct A {
890    int &&r;
891    constexpr A(int &&r) : r(static_cast<int &&>(r)) {}
892    constexpr A() : A(0) {
893      (void)+r; // expected-note {{outside its lifetime}}
894    }
895  };
896  constexpr int k = A().r; // expected-error {{constant expression}} expected-note {{in call to}}
897}
898
899namespace PR17331 {
900  template<typename T, unsigned int N>
901  constexpr T sum(const T (&arr)[N]) {
902    T result = 0;
903    for (T i : arr)
904      result += i;
905    return result;
906  }
907
908  constexpr int ARR[] = { 1, 2, 3, 4, 5 };
909  static_assert(sum(ARR) == 15, "");
910}
911
912namespace EmptyClass {
913  struct E1 {} e1;
914  union E2 {} e2; // expected-note 4{{here}}
915  struct E3 : E1 {} e3;
916
917  template<typename E>
918  constexpr int f(E &a, int kind) {
919    switch (kind) {
920    case 0: { E e(a); return 0; } // expected-note {{read}} expected-note {{in call}}
921    case 1: { E e(static_cast<E&&>(a)); return 0; } // expected-note {{read}} expected-note {{in call}}
922    case 2: { E e; e = a; return 0; } // expected-note {{read}} expected-note {{in call}}
923    case 3: { E e; e = static_cast<E&&>(a); return 0; } // expected-note {{read}} expected-note {{in call}}
924    }
925  }
926  constexpr int test1 = f(e1, 0);
927  constexpr int test2 = f(e2, 0); // expected-error {{constant expression}} expected-note {{in call}}
928  constexpr int test3 = f(e3, 0);
929  constexpr int test4 = f(e1, 1);
930  constexpr int test5 = f(e2, 1); // expected-error {{constant expression}} expected-note {{in call}}
931  constexpr int test6 = f(e3, 1);
932  constexpr int test7 = f(e1, 2);
933  constexpr int test8 = f(e2, 2); // expected-error {{constant expression}} expected-note {{in call}}
934  constexpr int test9 = f(e3, 2);
935  constexpr int testa = f(e1, 3);
936  constexpr int testb = f(e2, 3); // expected-error {{constant expression}} expected-note {{in call}}
937  constexpr int testc = f(e3, 3);
938}
939
940namespace SpeculativeEvalWrites {
941  // Ensure that we don't try to speculatively evaluate writes.
942  constexpr int f() {
943    int i = 0;
944    int a = 0;
945    // __builtin_object_size speculatively evaluates its first argument.
946    __builtin_object_size((i = 1, &a), 0);
947    return i;
948  }
949
950  static_assert(!f(), "");
951}
952
953namespace PR27989 {
954  constexpr int f(int n) {
955    int a = (n = 1, 0);
956    return n;
957  }
958  static_assert(f(0) == 1, "");
959}
960