p2-0x.cpp revision 3df61308ddfbdba0897b762a129b5a38750c87d0
1// RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify -fcxx-exceptions %s -fconstexpr-depth 128 2 3// A conditional-expression is a core constant expression unless it involves one 4// of the following as a potentially evaluated subexpression [...]: 5 6// - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant 7// expression, function invocation substitution (7.1.5 [dcl.constexpr]) 8// replaces each occurrence of this in a constexpr member function with a 9// pointer to the class object. -end note]; 10struct This { 11 int this1 : this1; // expected-error {{undeclared}} 12 int this2 : this->this1; // expected-error {{invalid}} 13 void this3() { 14 int n1[this->this1]; // expected-warning {{variable length array}} 15 int n2[this1]; // expected-warning {{variable length array}} 16 (void)n1, (void)n2; 17 } 18}; 19 20// - an invocation of a function other than a constexpr constructor for a 21// literal class or a constexpr function [ Note: Overload resolution (13.3) 22// is applied as usual - end note ]; 23struct NonConstexpr1 { 24 static int f() { return 1; } // expected-note {{here}} 25 int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}} 26}; 27struct NonConstexpr2 { 28 constexpr NonConstexpr2(); // expected-note {{here}} 29 int n; 30}; 31struct NonConstexpr3 { 32 NonConstexpr3(); 33 int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}} 34}; 35struct NonConstexpr4 { 36 NonConstexpr4(); // expected-note {{declared here}} 37 int n; 38}; 39struct NonConstexpr5 { 40 int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-constexpr constructor 'NonConstexpr4' cannot be used in a constant expression}} 41}; 42 43// - an invocation of an undefined constexpr function or an undefined 44// constexpr constructor; 45struct UndefinedConstexpr { 46 constexpr UndefinedConstexpr(); 47 static constexpr int undefinedConstexpr1(); // expected-note {{here}} 48 int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}} 49}; 50 51// - an invocation of a constexpr function with arguments that, when substituted 52// by function invocation substitution (7.1.5), do not produce a constant 53// expression; 54namespace NonConstExprReturn { 55 static constexpr const int &id_ref(const int &n) { 56 return n; // expected-note {{reference to temporary cannot be returned from a constexpr function}} 57 } 58 struct NonConstExprFunction { 59 int n : id_ref( // expected-error {{constant expression}} expected-note {{in call to 'id_ref(16)'}} 60 16 // expected-note {{temporary created here}} 61 ); 62 }; 63 constexpr const int *address_of(const int &a) { 64 return &a; // expected-note {{pointer to 'n' cannot be returned from a constexpr function}} 65 } 66 constexpr const int *return_param(int n) { // expected-note {{declared here}} 67 return address_of(n); // expected-note {{in call to 'address_of(n)'}} 68 } 69 struct S { 70 int n : *return_param(0); // expected-error {{constant expression}} expected-note {{in call to 'return_param(0)'}} 71 }; 72} 73 74// - an invocation of a constexpr constructor with arguments that, when 75// substituted by function invocation substitution (7.1.5), do not produce all 76// constant expressions for the constructor calls and full-expressions in the 77// mem-initializers (including conversions); 78namespace NonConstExprCtor { 79 struct T { 80 constexpr T(const int &r) : 81 r(r) { // expected-note 2{{reference to temporary cannot be used to initialize a member in a constant expression}} 82 } 83 const int &r; 84 }; 85 constexpr int n = 0; 86 constexpr T t1(n); // ok 87 constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(0)'}} 88 89 struct S { 90 int n : T(4).r; // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(4)'}} 91 }; 92} 93 94// - an invocation of a constexpr function or a constexpr constructor that would 95// exceed the implementation-defined recursion limits (see Annex B); 96namespace RecursionLimits { 97 constexpr int RecurseForever(int n) { 98 return n + RecurseForever(n+1); // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'RecurseForever(}} expected-note {{skipping 118 calls}} 99 } 100 struct AlsoRecurseForever { 101 constexpr AlsoRecurseForever(int n) : 102 n(AlsoRecurseForever(n+1).n) // expected-note {{constexpr evaluation exceeded maximum depth of 128 calls}} expected-note 9{{in call to 'AlsoRecurseForever(}} expected-note {{skipping 118 calls}} 103 {} 104 int n; 105 }; 106 struct S { 107 int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}} 108 int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}} 109 }; 110} 111 112// FIXME: 113// - an operation that would have undefined behavior [Note: including, for 114// example, signed integer overflow (Clause 5 [expr]), certain pointer 115// arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain 116// shift operations (5.8 [expr.shift]) -end note]; 117namespace UndefinedBehavior { 118 void f(int n) { 119 switch (n) { 120 case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}} 121 case (int)0x80000000u: // ok 122 case (int)10000000000ll: // expected-note {{here}} 123 case (unsigned int)10000000000ll: // expected-error {{duplicate case value}} 124 case (int)(unsigned)(long long)4.4e9: // ok 125 case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value 1.0E+300 is outside the range of representable values of type 'float'}} 126 case (int)((float)1e37 / 1e30): // ok 127 case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value 65536 is outside the range of representable values of type 'half'}} 128 break; 129 } 130 } 131 132 constexpr int int_min = ~0x7fffffff; 133 constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 134 constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}} 135 constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}} 136 constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 137 constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 138 139 constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}} 140 constexpr int shl_0 = 0 << 0; // ok 141 constexpr int shl_31 = 0 << 31; // ok 142 constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}} expected-warning {{>= width of type}} 143 constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok 144 constexpr int shl_unsigned_into_sign = 1u << 31; // ok 145 constexpr int shl_unsigned_overflow = 1024u << 31; // ok 146 constexpr int shl_signed_negative = (-3) << 1; // expected-error {{constant expression}} expected-note {{left shift of negative value -3}} 147 constexpr int shl_signed_ok = 1 << 30; // ok 148 constexpr int shl_signed_into_sign = 1 << 31; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 149 constexpr int shl_signed_overflow = 1024 << 31; // expected-error {{constant expression}} expected-note {{value 2199023255552 is outside the range}} expected-warning {{requires 43 bits to represent}} 150 constexpr int shl_signed_ok2 = 1024 << 20; // ok 151 152 constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}} 153 constexpr int shr_0 = 0 >> 0; // ok 154 constexpr int shr_31 = 0 >> 31; // ok 155 constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}} expected-warning {{>= width of type}} 156 157 struct S { 158 int m; 159 }; 160 constexpr S s = { 5 }; // expected-note {{declared here}} 161 constexpr const int *p = &s.m + 1; 162 constexpr const int &f(const int *q) { 163 return q[0]; // expected-note {{dereferenced pointer past the end of subobject of 's' is not a constant expression}} 164 } 165 constexpr int n = (f(p), 0); // expected-error {{constant expression}} expected-note {{in call to 'f(&s.m + 1)'}} 166 struct T { 167 int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 168 }; 169 170 namespace Ptr { 171 struct A {}; 172 struct B : A { int n; }; 173 B a[3][3]; 174 constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}} 175 B b = {}; 176 constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}} 177 constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}} 178 constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}} 179 constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}} 180 181 constexpr A *na = nullptr; 182 constexpr B *nb = nullptr; 183 constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}} 184 constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}} 185 static_assert((A*)nb == 0, ""); 186 static_assert((B*)na == 0, ""); 187 constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}} 188 constexpr const int &np = (*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot access array element of null pointer}} 189 } 190} 191 192// - a lambda-expression (5.1.2); 193struct Lambda { 194 // FIXME: clang crashes when trying to parse this! Revisit this check once 195 // lambdas are fully implemented. 196 //int n : []{ return 1; }(); 197}; 198 199// - an lvalue-to-rvalue conversion (4.1) unless it is applied to 200namespace LValueToRValue { 201 // - a non-volatile glvalue of integral or enumeration type that refers to a 202 // non-volatile const object with a preceding initialization, initialized 203 // with a constant expression [Note: a string literal (2.14.5 [lex.string]) 204 // corresponds to an array of such objects. -end note], or 205 volatile const int vi = 1; // expected-note {{here}} 206 const int ci = 1; 207 volatile const int &vrci = ci; 208 static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}} 209 static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}} 210 static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 211 212 // - a non-volatile glvalue of literal type that refers to a non-volatile 213 // object defined with constexpr, or that refers to a sub-object of such an 214 // object, or 215 struct S { 216 constexpr S(int=0) : i(1), v(1) {} 217 constexpr S(const S &s) : i(2), v(2) {} 218 int i; 219 volatile int v; 220 }; 221 constexpr S s; 222 constexpr volatile S vs; // expected-note {{here}} 223 constexpr const volatile S &vrs = s; 224 static_assert(s.i, ""); 225 static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 226 static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 227 static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}} 228 static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 229 230 // - a non-volatile glvalue of literal type that refers to a non-volatile 231 // temporary object whose lifetime has not ended, initialized with a 232 // constant expression; 233 constexpr volatile S f() { return S(); } 234 static_assert(f().i, ""); // ok! there's no lvalue-to-rvalue conversion here! 235 static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{subexpression}} 236} 237 238// FIXME: 239// 240// DR1312: The proposed wording for this defect has issues, so we ignore this 241// bullet and instead prohibit casts from pointers to cv void (see core-20842 242// and core-20845). 243// 244// - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a 245// glvalue of type cv1 T that refers to an object of type cv2 U, where T and U 246// are neither the same type nor similar types (4.4 [conv.qual]); 247 248// FIXME: 249// - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that 250// refers to a non-active member of a union or a subobject thereof; 251 252// - an id-expression that refers to a variable or data member of reference type 253// unless the reference has a preceding initialization, initialized with a 254// constant expression; 255namespace References { 256 const int a = 2; 257 int &b = *const_cast<int*>(&a); 258 int c = 10; // expected-note 2 {{here}} 259 int &d = c; 260 constexpr int e = 42; 261 int &f = const_cast<int&>(e); 262 extern int &g; 263 constexpr int &h(); // expected-note 2{{here}} 264 int &i = h(); // expected-note {{here}} expected-note {{undefined function 'h' cannot be used in a constant expression}} 265 constexpr int &j() { return b; } 266 int &k = j(); 267 268 struct S { 269 int A : a; 270 int B : b; 271 int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 272 int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 273 int D2 : &d - &c + 1; 274 int E : e / 2; 275 int F : f - 11; 276 int G : g; // expected-error {{constant expression}} 277 int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}} 278 int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}} 279 int J : j(); 280 int K : k; 281 }; 282} 283 284// - a dynamic_cast (5.2.7); 285namespace DynamicCast { 286 struct S { int n; }; 287 constexpr S s { 16 }; 288 struct T { 289 int n : dynamic_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{dynamic_cast}} 290 }; 291} 292 293// - a reinterpret_cast (5.2.10); 294namespace ReinterpretCast { 295 struct S { int n; }; 296 constexpr S s { 16 }; 297 struct T { 298 int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 299 }; 300 struct U { 301 int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 302 }; 303} 304 305// - a pseudo-destructor call (5.2.4); 306namespace PseudoDtor { 307 int k; 308 typedef int I; 309 struct T { 310 int n : (k.~I(), 0); // expected-error {{constant expression}} expected-note{{subexpression}} 311 }; 312} 313 314// - increment or decrement operations (5.2.6, 5.3.2); 315namespace IncDec { 316 int k = 2; 317 struct T { 318 int n : ++k; // expected-error {{constant expression}} 319 int m : --k; // expected-error {{constant expression}} 320 }; 321} 322 323// - a typeid expression (5.2.8) whose operand is of a polymorphic class type; 324namespace std { 325 struct type_info { 326 virtual ~type_info(); 327 const char *name; 328 }; 329} 330namespace TypeId { 331 struct S { virtual void f(); }; 332 constexpr S *p = 0; 333 constexpr const std::type_info &ti1 = typeid(*p); // expected-error {{must be initialized by a constant expression}} expected-note {{typeid applied to expression of polymorphic type 'TypeId::S'}} 334 335 struct T {} t; 336 constexpr const std::type_info &ti2 = typeid(t); 337} 338 339// - a new-expression (5.3.4); 340// - a delete-expression (5.3.5); 341namespace NewDelete { 342 int *p = 0; 343 struct T { 344 int n : *new int(4); // expected-error {{constant expression}} expected-note {{subexpression}} 345 int m : (delete p, 2); // expected-error {{constant expression}} expected-note {{subexpression}} 346 }; 347} 348 349// - a relational (5.9) or equality (5.10) operator where the result is 350// unspecified; 351namespace UnspecifiedRelations { 352 int a, b; 353 constexpr int *p = &a, *q = &b; 354 // C++11 [expr.rel]p2: If two pointers p and q of the same type point to 355 // different objects that are not members of the same array or to different 356 // functions, or if only one of them is null, the results of p<q, p>q, p<=q, 357 // and p>=q are unspecified. 358 constexpr bool u1 = p < q; // expected-error {{constant expression}} 359 constexpr bool u2 = p > q; // expected-error {{constant expression}} 360 constexpr bool u3 = p <= q; // expected-error {{constant expression}} 361 constexpr bool u4 = p >= q; // expected-error {{constant expression}} 362 constexpr bool u5 = p < 0; // expected-error {{constant expression}} 363 constexpr bool u6 = p <= 0; // expected-error {{constant expression}} 364 constexpr bool u7 = p > 0; // expected-error {{constant expression}} 365 constexpr bool u8 = p >= 0; // expected-error {{constant expression}} 366 constexpr bool u9 = 0 < q; // expected-error {{constant expression}} 367 constexpr bool u10 = 0 <= q; // expected-error {{constant expression}} 368 constexpr bool u11 = 0 > q; // expected-error {{constant expression}} 369 constexpr bool u12 = 0 >= q; // expected-error {{constant expression}} 370 void f(), g(); 371 372 constexpr void (*pf)() = &f, (*pg)() = &g; 373 constexpr bool u13 = pf < pg; // expected-error {{constant expression}} 374 constexpr bool u14 = pf == pg; 375 376 // FIXME: 377 // If two pointers point to non-static data members of the same object with 378 // different access control, the result is unspecified. 379 380 // [expr.rel]p3: Pointers to void can be compared [...] if both pointers 381 // represent the same address or are both the null pointer [...]; otherwise 382 // the result is unspecified. 383 struct S { int a, b; } s; 384 constexpr void *null = 0; 385 constexpr void *pv = (void*)&s.a; 386 constexpr void *qv = (void*)&s.b; 387 constexpr bool v1 = null < 0; 388 constexpr bool v2 = null < pv; // expected-error {{constant expression}} 389 constexpr bool v3 = null == pv; // ok 390 constexpr bool v4 = qv == pv; // ok 391 constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}} 392 constexpr bool v6 = qv > null; // expected-error {{constant expression}} 393 constexpr bool v7 = qv <= (void*)&s.b; // ok 394 constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}} 395 396 // FIXME: Implement comparisons of pointers to members. 397 // [expr.eq]p2: If either is a pointer to a virtual member function and 398 // neither is null, the result is unspecified. 399} 400 401// - an assignment or a compound assignment (5.17); or 402namespace Assignment { 403 int k; 404 struct T { 405 int n : (k = 9); // expected-error {{constant expression}} 406 int m : (k *= 2); // expected-error {{constant expression}} 407 }; 408 409 struct Literal { 410 constexpr Literal(const char *name) : name(name) {} 411 const char *name; 412 }; 413 struct Expr { 414 constexpr Expr(Literal l) : IsLiteral(true), l(l) {} 415 bool IsLiteral; 416 union { 417 Literal l; 418 // ... 419 }; 420 }; 421 struct MulEq { 422 constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {} 423 Expr LHS; 424 Expr RHS; 425 }; 426 constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); } 427 Literal a("a"); 428 Literal b("b"); 429 MulEq c = a *= b; // ok 430} 431 432// - a throw-expression (15.1) 433namespace Throw { 434 struct S { 435 int n : (throw "hello", 10); // expected-error {{constant expression}} expected-note {{subexpression}} 436 }; 437} 438 439// PR9999 440template<unsigned int v> 441class bitWidthHolding { 442public: 443 static const 444 unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1); 445}; 446 447static const int width=bitWidthHolding<255>::width; 448 449template<bool b> 450struct always_false { 451 static const bool value = false; 452}; 453 454template<bool b> 455struct and_or { 456 static const bool and_value = b && and_or<always_false<b>::value>::and_value; 457 static const bool or_value = !b || and_or<always_false<b>::value>::or_value; 458}; 459 460static const bool and_value = and_or<true>::and_value; 461static const bool or_value = and_or<true>::or_value; 462 463static_assert(and_value == false, ""); 464static_assert(or_value == true, ""); 465