constant-expression-cxx11.cpp revision 83587db1bda97f45d2b5a4189e584e2a18be511a
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', ""); 410 411} 412 413namespace Array { 414 415template<typename Iter> 416constexpr auto Sum(Iter begin, Iter end) -> decltype(+*begin) { 417 return begin == end ? 0 : *begin + Sum(begin+1, end); 418} 419 420constexpr int xs[] = { 1, 2, 3, 4, 5 }; 421constexpr int ys[] = { 5, 4, 3, 2, 1 }; 422constexpr int sum_xs = Sum(begin(xs), end(xs)); 423static_assert(sum_xs == 15, ""); 424 425constexpr int ZipFoldR(int (*F)(int x, int y, int c), int n, 426 const int *xs, const int *ys, int c) { 427 return n ? F( 428 *xs, // expected-note {{read of dereferenced one-past-the-end pointer}} 429 *ys, 430 ZipFoldR(F, n-1, xs+1, ys+1, c)) // \ 431 expected-note {{in call to 'ZipFoldR(&SubMul, 2, &xs[4], &ys[4], 1)'}} \ 432 expected-note {{in call to 'ZipFoldR(&SubMul, 1, &xs[5], &ys[5], 1)'}} 433 : c; 434} 435constexpr int MulAdd(int x, int y, int c) { return x * y + c; } 436constexpr int InnerProduct = ZipFoldR(MulAdd, 5, xs, ys, 0); 437static_assert(InnerProduct == 35, ""); 438 439constexpr int SubMul(int x, int y, int c) { return (x - y) * c; } 440constexpr int DiffProd = ZipFoldR(SubMul, 2, xs+3, ys+3, 1); 441static_assert(DiffProd == 8, ""); 442static_assert(ZipFoldR(SubMul, 3, xs+3, ys+3, 1), ""); // \ 443 expected-error {{constant expression}} \ 444 expected-note {{in call to 'ZipFoldR(&SubMul, 3, &xs[3], &ys[3], 1)'}} 445 446constexpr const int *p = xs + 3; 447constexpr int xs4 = p[1]; // ok 448constexpr int xs5 = p[2]; // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 449constexpr int xs6 = p[3]; // expected-error {{constant expression}} expected-note {{cannot refer to element 6}} 450constexpr int xs0 = p[-3]; // ok 451constexpr int xs_1 = p[-4]; // expected-error {{constant expression}} expected-note {{cannot refer to element -1}} 452 453constexpr int zs[2][2][2][2] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 }; 454static_assert(zs[0][0][0][0] == 1, ""); 455static_assert(zs[1][1][1][1] == 16, ""); 456static_assert(zs[0][0][0][2] == 3, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 457static_assert((&zs[0][0][0][2])[-1] == 2, ""); 458static_assert(**(**(zs + 1) + 1) == 11, ""); 459static_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}} 460static_assert(*(&(&(*(*&(&zs[2] - 1)[0] + 2 - 2))[2])[-1][2] - 2) == 11, ""); 461constexpr 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}} 462 463constexpr int fail(const int &p) { 464 return (&p)[64]; // expected-note {{cannot refer to element 64 of array of 2 elements}} 465} 466static_assert(fail(*(&(&(*(*&(&zs[2] - 1)[0] + 2 - 2))[2])[-1][2] - 2)) == 11, ""); // \ 467expected-error {{static_assert expression is not an integral constant expression}} \ 468expected-note {{in call to 'fail(zs[1][0][1][0])'}} 469 470constexpr int arr[40] = { 1, 2, 3, [8] = 4 }; // expected-warning {{C99 feature}} 471constexpr int SumNonzero(const int *p) { 472 return *p + (*p ? SumNonzero(p+1) : 0); 473} 474constexpr int CountZero(const int *p, const int *q) { 475 return p == q ? 0 : (*p == 0) + CountZero(p+1, q); 476} 477static_assert(SumNonzero(arr) == 6, ""); 478static_assert(CountZero(arr, arr + 40) == 36, ""); 479 480struct ArrayElem { 481 constexpr ArrayElem() : n(0) {} 482 int n; 483 constexpr int f() { return n; } 484}; 485struct ArrayRVal { 486 constexpr ArrayRVal() {} 487 ArrayElem elems[10]; 488}; 489static_assert(ArrayRVal().elems[3].f() == 0, ""); 490 491} 492 493namespace DependentValues { 494 495struct I { int n; typedef I V[10]; }; 496I::V x, y; 497template<bool B> struct S { 498 int k; 499 void f() { 500 I::V &cells = B ? x : y; 501 I &i = cells[k]; 502 switch (i.n) {} 503 } 504}; 505 506} 507 508namespace Class { 509 510struct A { constexpr A(int a, int b) : k(a + b) {} int k; }; 511constexpr int fn(const A &a) { return a.k; } 512static_assert(fn(A(4,5)) == 9, ""); 513 514struct B { int n; int m; } constexpr b = { 0, b.n }; // expected-warning {{uninitialized}} 515struct C { 516 constexpr C(C *this_) : m(42), n(this_->m) {} // ok 517 int m, n; 518}; 519struct D { 520 C c; 521 constexpr D() : c(&c) {} 522}; 523static_assert(D().c.n == 42, ""); 524 525struct E { 526 constexpr E() : p(&p) {} 527 void *p; 528}; 529constexpr const E &e1 = E(); // expected-error {{constant expression}} expected-note {{reference to temporary is not a constant expression}} expected-note {{temporary created here}} 530// This is a constant expression if we elide the copy constructor call, and 531// is not a constant expression if we don't! But we do, so it is. 532constexpr E e2 = E(); 533static_assert(e2.p == &e2.p, ""); 534constexpr E e3; 535static_assert(e3.p == &e3.p, ""); 536 537extern const class F f; 538struct F { 539 constexpr F() : p(&f.p) {} 540 const void *p; 541}; 542constexpr F f; 543 544struct G { 545 struct T { 546 constexpr T(T *p) : u1(), u2(p) {} 547 union U1 { 548 constexpr U1() {} 549 int a, b = 42; 550 } u1; 551 union U2 { 552 constexpr U2(T *p) : c(p->u1.b) {} 553 int c, d; 554 } u2; 555 } t; 556 constexpr G() : t(&t) {} 557} constexpr g; 558 559static_assert(g.t.u1.a == 42, ""); // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}} 560static_assert(g.t.u1.b == 42, ""); 561static_assert(g.t.u2.c == 42, ""); 562static_assert(g.t.u2.d == 42, ""); // expected-error {{constant expression}} expected-note {{read of member 'd' of union with active member 'c'}} 563 564struct S { 565 int a, b; 566 const S *p; 567 double d; 568 const char *q; 569 570 constexpr S(int n, const S *p) : a(5), b(n), p(p), d(n), q("hello") {} 571}; 572 573S global(43, &global); 574 575static_assert(S(15, &global).b == 15, ""); 576 577constexpr bool CheckS(const S &s) { 578 return s.a == 5 && s.b == 27 && s.p == &global && s.d == 27. && s.q[3] == 'l'; 579} 580static_assert(CheckS(S(27, &global)), ""); 581 582struct Arr { 583 char arr[3]; 584 constexpr Arr() : arr{'x', 'y', 'z'} {} 585}; 586constexpr int hash(Arr &&a) { 587 return a.arr[0] + a.arr[1] * 0x100 + a.arr[2] * 0x10000; 588} 589constexpr int k = hash(Arr()); 590static_assert(k == 0x007a7978, ""); 591 592 593struct AggregateInit { 594 const char &c; 595 int n; 596 double d; 597 int arr[5]; 598 void *p; 599}; 600 601constexpr AggregateInit agg1 = { "hello"[0] }; 602 603static_assert(strcmp_ce(&agg1.c, "hello") == 0, ""); 604static_assert(agg1.n == 0, ""); 605static_assert(agg1.d == 0.0, ""); 606static_assert(agg1.arr[-1] == 0, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element -1}} 607static_assert(agg1.arr[0] == 0, ""); 608static_assert(agg1.arr[4] == 0, ""); 609static_assert(agg1.arr[5] == 0, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end}} 610static_assert(agg1.p == nullptr, ""); 611 612namespace SimpleDerivedClass { 613 614struct B { 615 constexpr B(int n) : a(n) {} 616 int a; 617}; 618struct D : B { 619 constexpr D(int n) : B(n) {} 620}; 621constexpr D d(3); 622static_assert(d.a == 3, ""); 623 624} 625 626struct Bottom { constexpr Bottom() {} }; 627struct Base : Bottom { 628 constexpr Base(int a = 42, const char *b = "test") : a(a), b(b) {} 629 int a; 630 const char *b; 631}; 632struct Base2 : Bottom { 633 constexpr Base2(const int &r) : r(r) {} 634 int q = 123; 635 const int &r; 636}; 637struct Derived : Base, Base2 { 638 constexpr Derived() : Base(76), Base2(a) {} 639 int c = r + b[1]; 640}; 641 642constexpr bool operator==(const Base &a, const Base &b) { 643 return a.a == b.a && strcmp_ce(a.b, b.b) == 0; 644} 645 646constexpr Base base; 647constexpr Base base2(76); 648constexpr Derived derived; 649static_assert(derived.a == 76, ""); 650static_assert(derived.b[2] == 's', ""); 651static_assert(derived.c == 76 + 'e', ""); 652static_assert(derived.q == 123, ""); 653static_assert(derived.r == 76, ""); 654static_assert(&derived.r == &derived.a, ""); 655 656static_assert(!(derived == base), ""); 657static_assert(derived == base2, ""); 658 659constexpr Bottom &bot1 = (Base&)derived; 660constexpr Bottom &bot2 = (Base2&)derived; 661static_assert(&bot1 != &bot2, ""); 662 663constexpr Bottom *pb1 = (Base*)&derived; 664constexpr Bottom *pb2 = (Base2*)&derived; 665static_assert(&pb1 != &pb2, ""); 666static_assert(pb1 == &bot1, ""); 667static_assert(pb2 == &bot2, ""); 668 669constexpr Base2 &fail = (Base2&)bot1; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base2'}} 670constexpr Base &fail2 = (Base&)*pb2; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base'}} 671constexpr Base2 &ok2 = (Base2&)bot2; 672static_assert(&ok2 == &derived, ""); 673 674constexpr Base2 *pfail = (Base2*)pb1; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base2'}} 675constexpr Base *pfail2 = (Base*)&bot2; // expected-error {{constant expression}} expected-note {{cannot cast object of dynamic type 'const Class::Derived' to type 'Class::Base'}} 676constexpr Base2 *pok2 = (Base2*)pb2; 677static_assert(pok2 == &derived, ""); 678static_assert(&ok2 == pok2, ""); 679static_assert((Base2*)(Derived*)(Base*)pb1 == pok2, ""); 680static_assert((Derived*)(Base*)pb1 == (Derived*)pok2, ""); 681 682constexpr Base *nullB = 42 - 6 * 7; 683static_assert((Bottom*)nullB == 0, ""); 684static_assert((Derived*)nullB == 0, ""); 685static_assert((void*)(Bottom*)nullB == (void*)(Derived*)nullB, ""); 686 687namespace ConversionOperators { 688 689struct T { 690 constexpr T(int n) : k(5*n - 3) {} 691 constexpr operator int() { return k; } 692 int k; 693}; 694 695struct S { 696 constexpr S(int n) : k(2*n + 1) {} 697 constexpr operator int() { return k; } 698 constexpr operator T() { return T(k); } 699 int k; 700}; 701 702constexpr bool check(T a, T b) { return a == b.k; } 703 704static_assert(S(5) == 11, ""); 705static_assert(check(S(5), 11), ""); 706 707} 708 709} 710 711namespace Temporaries { 712 713struct S { 714 constexpr S() {} 715 constexpr int f(); 716}; 717struct T : S { 718 constexpr T(int n) : S(), n(n) {} 719 int n; 720}; 721constexpr int S::f() { 722 // 'this' must be the postfix-expression in a class member access expression, 723 // so we can't just use 724 // return static_cast<T*>(this)->n; 725 return this->*(int(S::*))&T::n; 726} 727// The T temporary is implicitly cast to an S subobject, but we can recover the 728// T full-object via a base-to-derived cast, or a derived-to-base-casted member 729// pointer. 730static_assert(T(3).f() == 3, ""); 731 732constexpr int f(const S &s) { 733 return static_cast<const T&>(s).n; 734} 735constexpr int n = f(T(5)); 736static_assert(f(T(5)) == 5, ""); 737 738constexpr bool b(int n) { return &n; } 739static_assert(b(0), ""); 740 741} 742 743namespace Union { 744 745union U { 746 int a; 747 int b; 748}; 749 750constexpr U u[4] = { { .a = 0 }, { .b = 1 }, { .a = 2 }, { .b = 3 } }; // expected-warning 4{{C99 feature}} 751static_assert(u[0].a == 0, ""); 752static_assert(u[0].b, ""); // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}} 753static_assert(u[1].b == 1, ""); 754static_assert((&u[1].b)[1] == 2, ""); // expected-error {{constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 755static_assert(*(&(u[1].b) + 1 + 1) == 3, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element 2 of non-array object}} 756static_assert((&(u[1]) + 1 + 1)->b == 3, ""); 757 758constexpr U v = {}; 759static_assert(v.a == 0, ""); 760 761union Empty {}; 762constexpr Empty e = {}; 763 764// Make sure we handle trivial copy constructors for unions. 765constexpr U x = {42}; 766constexpr U y = x; 767static_assert(y.a == 42, ""); 768static_assert(y.b == 42, ""); // expected-error {{constant expression}} expected-note {{'b' of union with active member 'a'}} 769 770} 771 772namespace MemberPointer { 773 struct A { 774 constexpr A(int n) : n(n) {} 775 int n; 776 constexpr int f() { return n + 3; } 777 }; 778 constexpr A a(7); 779 static_assert(A(5).*&A::n == 5, ""); 780 static_assert((&a)->*&A::n == 7, ""); 781 static_assert((A(8).*&A::f)() == 11, ""); 782 static_assert(((&a)->*&A::f)() == 10, ""); 783 784 struct B : A { 785 constexpr B(int n, int m) : A(n), m(m) {} 786 int m; 787 constexpr int g() { return n + m + 1; } 788 }; 789 constexpr B b(9, 13); 790 static_assert(B(4, 11).*&A::n == 4, ""); 791 static_assert(B(4, 11).*&B::m == 11, ""); 792 static_assert(B(4, 11).*(int(A::*))&B::m == 11, ""); 793 static_assert((&b)->*&A::n == 9, ""); 794 static_assert((&b)->*&B::m == 13, ""); 795 static_assert((&b)->*(int(A::*))&B::m == 13, ""); 796 static_assert((B(4, 11).*&A::f)() == 7, ""); 797 static_assert((B(4, 11).*&B::g)() == 16, ""); 798 static_assert((B(4, 11).*(int(A::*)()const)&B::g)() == 16, ""); 799 static_assert(((&b)->*&A::f)() == 12, ""); 800 static_assert(((&b)->*&B::g)() == 23, ""); 801 static_assert(((&b)->*(int(A::*)()const)&B::g)() == 23, ""); 802 803 struct S { 804 constexpr S(int m, int n, int (S::*pf)() const, int S::*pn) : 805 m(m), n(n), pf(pf), pn(pn) {} 806 constexpr S() : m(), n(), pf(&S::f), pn(&S::n) {} 807 808 constexpr int f() { return this->*pn; } 809 virtual int g() const; 810 811 int m, n; 812 int (S::*pf)() const; 813 int S::*pn; 814 }; 815 816 constexpr int S::*pm = &S::m; 817 constexpr int S::*pn = &S::n; 818 constexpr int (S::*pf)() const = &S::f; 819 constexpr int (S::*pg)() const = &S::g; 820 821 constexpr S s(2, 5, &S::f, &S::m); 822 823 static_assert((s.*&S::f)() == 2, ""); 824 static_assert((s.*s.pf)() == 2, ""); 825 826 static_assert(pf == &S::f, ""); 827 static_assert(pf == s.*&S::pf, ""); 828 static_assert(pm == &S::m, ""); 829 static_assert(pm != pn, ""); 830 static_assert(s.pn != pn, ""); 831 static_assert(s.pn == pm, ""); 832 static_assert(pg != nullptr, ""); 833 static_assert(pf != nullptr, ""); 834 static_assert((int S::*)nullptr == nullptr, ""); 835 static_assert(pg == pg, ""); // expected-error {{constant expression}} expected-note {{comparison of pointer to virtual member function 'g' has unspecified value}} 836 static_assert(pf != pg, ""); // expected-error {{constant expression}} expected-note {{comparison of pointer to virtual member function 'g' has unspecified value}} 837 838 template<int n> struct T : T<n-1> {}; 839 template<> struct T<0> { int n; }; 840 template<> struct T<30> : T<29> { int m; }; 841 842 T<17> t17; 843 T<30> t30; 844 845 constexpr int (T<10>::*deepn) = &T<0>::n; 846 static_assert(&(t17.*deepn) == &t17.n, ""); 847 static_assert(deepn == &T<2>::n, ""); 848 849 constexpr int (T<15>::*deepm) = (int(T<10>::*))&T<30>::m; 850 constexpr int *pbad = &(t17.*deepm); // expected-error {{constant expression}} 851 static_assert(&(t30.*deepm) == &t30.m, ""); 852 static_assert(deepm == &T<50>::m, ""); 853 static_assert(deepm != deepn, ""); 854 855 constexpr T<5> *p17_5 = &t17; 856 constexpr T<13> *p17_13 = (T<13>*)p17_5; 857 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>'}} 858 static_assert(&(p17_5->*(int(T<3>::*))deepn) == &t17.n, ""); 859 static_assert(&(p17_13->*deepn) == &t17.n, ""); 860 constexpr int *pbad2 = &(p17_13->*(int(T<9>::*))deepm); // expected-error {{constant expression}} 861 862 constexpr T<5> *p30_5 = &t30; 863 constexpr T<23> *p30_23 = (T<23>*)p30_5; 864 constexpr T<13> *p30_13 = p30_23; 865 static_assert(&(p30_5->*(int(T<3>::*))deepn) == &t30.n, ""); 866 static_assert(&(p30_13->*deepn) == &t30.n, ""); 867 static_assert(&(p30_23->*deepn) == &t30.n, ""); 868 static_assert(&(p30_5->*(int(T<2>::*))deepm) == &t30.m, ""); 869 static_assert(&(((T<17>*)p30_13)->*deepm) == &t30.m, ""); 870 static_assert(&(p30_23->*deepm) == &t30.m, ""); 871 872 struct Base { int n; }; 873 template<int N> struct Mid : Base {}; 874 struct Derived : Mid<0>, Mid<1> {}; 875 static_assert(&Mid<0>::n == &Mid<1>::n, ""); 876 static_assert((int Derived::*)(int Mid<0>::*)&Mid<0>::n != 877 (int Derived::*)(int Mid<1>::*)&Mid<1>::n, ""); 878 static_assert(&Mid<0>::n == (int Mid<0>::*)&Base::n, ""); 879} 880 881namespace ArrayBaseDerived { 882 883 struct Base { 884 constexpr Base() {} 885 int n = 0; 886 }; 887 struct Derived : Base { 888 constexpr Derived() {} 889 constexpr const int *f() { return &n; } 890 }; 891 892 constexpr Derived a[10]; 893 constexpr Derived *pd3 = const_cast<Derived*>(&a[3]); 894 constexpr Base *pb3 = const_cast<Derived*>(&a[3]); 895 static_assert(pb3 == pd3, ""); 896 897 // pb3 does not point to an array element. 898 constexpr Base *pb4 = pb3 + 1; // ok, one-past-the-end pointer. 899 constexpr int pb4n = pb4->n; // expected-error {{constant expression}} expected-note {{cannot access field of pointer past the end}} 900 constexpr Base *err_pb5 = pb3 + 2; // expected-error {{constant expression}} expected-note {{cannot refer to element 2}} expected-note {{here}} 901 constexpr int err_pb5n = err_pb5->n; // expected-error {{constant expression}} expected-note {{initializer of 'err_pb5' is not a constant expression}} 902 constexpr Base *err_pb2 = pb3 - 1; // expected-error {{constant expression}} expected-note {{cannot refer to element -1}} expected-note {{here}} 903 constexpr int err_pb2n = err_pb2->n; // expected-error {{constant expression}} expected-note {{initializer of 'err_pb2'}} 904 constexpr Base *pb3a = pb4 - 1; 905 906 // pb4 does not point to a Derived. 907 constexpr Derived *err_pd4 = (Derived*)pb4; // expected-error {{constant expression}} expected-note {{cannot access derived class of pointer past the end}} 908 constexpr Derived *pd3a = (Derived*)pb3a; 909 constexpr int pd3n = pd3a->n; 910 911 // pd3a still points to the Derived array. 912 constexpr Derived *pd6 = pd3a + 3; 913 static_assert(pd6 == &a[6], ""); 914 constexpr Derived *pd9 = pd6 + 3; 915 constexpr Derived *pd10 = pd6 + 4; 916 constexpr int pd9n = pd9->n; // ok 917 constexpr int err_pd10n = pd10->n; // expected-error {{constant expression}} expected-note {{cannot access base class of pointer past the end}} 918 constexpr int pd0n = pd10[-10].n; 919 constexpr int err_pdminus1n = pd10[-11].n; // expected-error {{constant expression}} expected-note {{cannot refer to element -1 of}} 920 921 constexpr Base *pb9 = pd9; 922 constexpr const int *(Base::*pfb)() const = 923 static_cast<const int *(Base::*)() const>(&Derived::f); 924 static_assert((pb9->*pfb)() == &a[9].n, ""); 925} 926 927namespace Complex { 928 929class complex { 930 int re, im; 931public: 932 constexpr complex(int re = 0, int im = 0) : re(re), im(im) {} 933 constexpr complex(const complex &o) : re(o.re), im(o.im) {} 934 constexpr complex operator-() const { return complex(-re, -im); } 935 friend constexpr complex operator+(const complex &l, const complex &r) { 936 return complex(l.re + r.re, l.im + r.im); 937 } 938 friend constexpr complex operator-(const complex &l, const complex &r) { 939 return l + -r; 940 } 941 friend constexpr complex operator*(const complex &l, const complex &r) { 942 return complex(l.re * r.re - l.im * r.im, l.re * r.im + l.im * r.re); 943 } 944 friend constexpr bool operator==(const complex &l, const complex &r) { 945 return l.re == r.re && l.im == r.im; 946 } 947 constexpr bool operator!=(const complex &r) const { 948 return re != r.re || im != r.im; 949 } 950 constexpr int real() const { return re; } 951 constexpr int imag() const { return im; } 952}; 953 954constexpr complex i = complex(0, 1); 955constexpr complex k = (3 + 4*i) * (6 - 4*i); 956static_assert(complex(1,0).real() == 1, ""); 957static_assert(complex(1,0).imag() == 0, ""); 958static_assert(((complex)1).imag() == 0, ""); 959static_assert(k.real() == 34, ""); 960static_assert(k.imag() == 12, ""); 961static_assert(k - 34 == 12*i, ""); 962static_assert((complex)1 == complex(1), ""); 963static_assert((complex)1 != complex(0, 1), ""); 964static_assert(complex(1) == complex(1), ""); 965static_assert(complex(1) != complex(0, 1), ""); 966constexpr complex makeComplex(int re, int im) { return complex(re, im); } 967static_assert(makeComplex(1,0) == complex(1), ""); 968static_assert(makeComplex(1,0) != complex(0, 1), ""); 969 970class complex_wrap : public complex { 971public: 972 constexpr complex_wrap(int re, int im = 0) : complex(re, im) {} 973 constexpr complex_wrap(const complex_wrap &o) : complex(o) {} 974}; 975 976static_assert((complex_wrap)1 == complex(1), ""); 977static_assert((complex)1 != complex_wrap(0, 1), ""); 978static_assert(complex(1) == complex_wrap(1), ""); 979static_assert(complex_wrap(1) != complex(0, 1), ""); 980constexpr complex_wrap makeComplexWrap(int re, int im) { 981 return complex_wrap(re, im); 982} 983static_assert(makeComplexWrap(1,0) == complex(1), ""); 984static_assert(makeComplexWrap(1,0) != complex(0, 1), ""); 985 986} 987 988namespace PR11595 { 989 struct A { constexpr bool operator==(int x) { return true; } }; 990 struct B { B(); A& x; }; 991 static_assert(B().x == 3, ""); // expected-error {{constant expression}} expected-note {{non-literal type 'PR11595::B' cannot be used in a constant expression}} 992 993 constexpr bool f(int k) { // expected-error {{constexpr function never produces a constant expression}} 994 return B().x == k; // expected-note {{non-literal type 'PR11595::B' cannot be used in a constant expression}} 995 } 996} 997 998namespace ExprWithCleanups { 999 struct A { A(); ~A(); int get(); }; 1000 constexpr int get(bool FromA) { return FromA ? A().get() : 1; } 1001 constexpr int n = get(false); 1002} 1003 1004namespace Volatile { 1005 1006volatile constexpr int n1 = 0; // expected-note {{here}} 1007volatile const int n2 = 0; // expected-note {{here}} 1008int n3 = 37; // expected-note {{declared here}} 1009 1010constexpr int m1 = n1; // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}} 1011constexpr int m2 = n2; // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}} 1012constexpr int m1b = const_cast<const int&>(n1); // expected-error {{constant expression}} expected-note {{read of volatile object 'n1'}} 1013constexpr int m2b = const_cast<const int&>(n2); // expected-error {{constant expression}} expected-note {{read of volatile object 'n2'}} 1014 1015struct T { int n; }; 1016const T t = { 42 }; // expected-note {{declared here}} 1017 1018constexpr int f(volatile int &&r) { 1019 return r; // expected-note {{read of volatile-qualified type 'volatile int'}} 1020} 1021constexpr int g(volatile int &&r) { 1022 return const_cast<int&>(r); // expected-note {{read of volatile temporary is not allowed in a constant expression}} 1023} 1024struct S { 1025 int j : f(0); // expected-error {{constant expression}} expected-note {{in call to 'f(0)'}} 1026 int k : g(0); // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'g(0)'}} 1027 int l : n3; // expected-error {{constant expression}} expected-note {{read of non-const variable}} 1028 int m : t.n; // expected-error {{constant expression}} expected-note {{read of non-constexpr variable}} 1029}; 1030 1031} 1032 1033namespace ExternConstexpr { 1034 extern constexpr int n = 0; 1035 extern constexpr int m; // expected-error {{constexpr variable declaration must be a definition}} 1036 void f() { 1037 extern constexpr int i; // expected-error {{constexpr variable declaration must be a definition}} 1038 constexpr int j = 0; 1039 constexpr int k; // expected-error {{default initialization of an object of const type}} 1040 } 1041} 1042 1043namespace ComplexConstexpr { 1044 constexpr _Complex float test1 = {}; 1045 constexpr _Complex float test2 = {1}; 1046 constexpr _Complex double test3 = {1,2}; 1047 constexpr _Complex int test4 = {4}; 1048 constexpr _Complex int test5 = 4; 1049 constexpr _Complex int test6 = {5,6}; 1050 typedef _Complex float fcomplex; 1051 constexpr fcomplex test7 = fcomplex(); 1052} 1053 1054namespace InstantiateCaseStmt { 1055 template<int x> constexpr int f() { return x; } 1056 template<int x> int g(int c) { switch(c) { case f<x>(): return 1; } return 0; } 1057 int gg(int c) { return g<4>(c); } 1058} 1059 1060namespace ConvertedConstantExpr { 1061 extern int &m; 1062 extern int &n; 1063 1064 constexpr int k = 4; 1065 int &m = const_cast<int&>(k); 1066 1067 // If we have nothing more interesting to say, ensure we don't produce a 1068 // useless note and instead just point to the non-constant subexpression. 1069 enum class E { 1070 em = m, 1071 en = n, // expected-error {{not a constant expression}} 1072 eo = (m + 1073 n // expected-error {{not a constant expression}} 1074 ), 1075 eq = reinterpret_cast<int>((int*)0) // expected-error {{not a constant expression}} expected-note {{reinterpret_cast}} 1076 }; 1077} 1078 1079namespace IndirectField { 1080 struct S { 1081 struct { // expected-warning {{GNU extension}} 1082 union { 1083 struct { // expected-warning {{GNU extension}} 1084 int a; 1085 int b; 1086 }; 1087 int c; 1088 }; 1089 int d; 1090 }; 1091 union { 1092 int e; 1093 int f; 1094 }; 1095 constexpr S(int a, int b, int d, int e) : a(a), b(b), d(d), e(e) {} 1096 constexpr S(int c, int d, int f) : c(c), d(d), f(f) {} 1097 }; 1098 1099 constexpr S s1(1, 2, 3, 4); 1100 constexpr S s2(5, 6, 7); 1101 1102 // FIXME: The diagnostics here do a very poor job of explaining which unnamed 1103 // member is active and which is requested. 1104 static_assert(s1.a == 1, ""); 1105 static_assert(s1.b == 2, ""); 1106 static_assert(s1.c == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}} 1107 static_assert(s1.d == 3, ""); 1108 static_assert(s1.e == 4, ""); 1109 static_assert(s1.f == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}} 1110 1111 static_assert(s2.a == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}} 1112 static_assert(s2.b == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}} 1113 static_assert(s2.c == 5, ""); 1114 static_assert(s2.d == 6, ""); 1115 static_assert(s2.e == 0, ""); // expected-error {{constant expression}} expected-note {{union with active member}} 1116 static_assert(s2.f == 7, ""); 1117} 1118 1119// DR1405: don't allow reading mutable members in constant expressions. 1120namespace MutableMembers { 1121 struct MM { 1122 mutable int n; // expected-note 3{{declared here}} 1123 } constexpr mm = { 4 }; 1124 constexpr int mmn = mm.n; // expected-error {{constant expression}} expected-note {{read of mutable member 'n' is not allowed in a constant expression}} 1125 int x = (mm.n = 1, 3); 1126 constexpr int mmn2 = mm.n; // expected-error {{constant expression}} expected-note {{read of mutable member 'n' is not allowed in a constant expression}} 1127 1128 // Here's one reason why allowing this would be a disaster... 1129 template<int n> struct Id { int k = n; }; 1130 int f() { 1131 constexpr MM m = { 0 }; 1132 ++m.n; 1133 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}} 1134 } 1135 1136 struct A { int n; }; 1137 struct B { mutable A a; }; // expected-note {{here}} 1138 struct C { B b; }; 1139 constexpr C c[3] = {}; 1140 constexpr int k = c[1].b.a.n; // expected-error {{constant expression}} expected-note {{mutable}} 1141} 1142 1143namespace Fold { 1144 1145 // This macro forces its argument to be constant-folded, even if it's not 1146 // otherwise a constant expression. 1147 #define fold(x) (__builtin_constant_p(x) ? (x) : (x)) 1148 1149 constexpr int n = (int)(char*)123; // expected-error {{constant expression}} expected-note {{reinterpret_cast}} 1150 constexpr int m = fold((int)(char*)123); // ok 1151 static_assert(m == 123, ""); 1152 1153 #undef fold 1154 1155} 1156 1157namespace DR1454 { 1158 1159constexpr const int &f(const int &n) { return n; } 1160constexpr int k1 = f(0); // ok 1161 1162struct Wrap { 1163 const int &value; 1164}; 1165constexpr const Wrap &g(const Wrap &w) { return w; } 1166constexpr int k2 = g({0}).value; // ok 1167 1168constexpr const int &i = 0; // expected-error {{constant expression}} expected-note {{temporary}} expected-note 2{{here}} 1169constexpr const int j = i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}} 1170 1171} 1172