p2-0x.cpp revision f72fccf533bca206af8e75d041c29db99e6a7f2c
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)10000000000ll: // expected-error {{constant expression}} expected-note {{value 10000000000 is outside the range of representable values of type 'int'}} expected-note {{here}} 122 case (int)0x80000000u: // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of representable values of type 'int'}} 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 struct S { 133 int m; 134 }; 135 constexpr S s = { 5 }; // expected-note {{declared here}} 136 constexpr const int *p = &s.m + 1; 137 constexpr const int &f(const int *q) { 138 return q[0]; // expected-note {{dereferenced pointer past the end of subobject of 's' is not a constant expression}} 139 } 140 constexpr int n = (f(p), 0); // expected-error {{constant expression}} expected-note {{in call to 'f(&s.m + 1)'}} 141 struct T { 142 int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 143 }; 144 145 namespace Ptr { 146 struct A {}; 147 struct B : A { int n; }; 148 B a[3][3]; 149 constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}} 150 B b = {}; 151 constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}} 152 constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}} 153 constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}} 154 constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}} 155 156 constexpr A *na = nullptr; 157 constexpr B *nb = nullptr; 158 constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}} 159 constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}} 160 static_assert((A*)nb == 0, ""); 161 static_assert((B*)na == 0, ""); 162 constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}} 163 constexpr const int &np = (*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot access array element of null pointer}} 164 } 165} 166 167// - a lambda-expression (5.1.2); 168struct Lambda { 169 // FIXME: clang crashes when trying to parse this! Revisit this check once 170 // lambdas are fully implemented. 171 //int n : []{ return 1; }(); 172}; 173 174// - an lvalue-to-rvalue conversion (4.1) unless it is applied to 175namespace LValueToRValue { 176 // - a non-volatile glvalue of integral or enumeration type that refers to a 177 // non-volatile const object with a preceding initialization, initialized 178 // with a constant expression [Note: a string literal (2.14.5 [lex.string]) 179 // corresponds to an array of such objects. -end note], or 180 volatile const int vi = 1; // expected-note {{here}} 181 const int ci = 1; 182 volatile const int &vrci = ci; 183 static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type 'const volatile int'}} 184 static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}} 185 static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 186 187 // - a non-volatile glvalue of literal type that refers to a non-volatile 188 // object defined with constexpr, or that refers to a sub-object of such an 189 // object, or 190 struct S { 191 constexpr S(int=0) : i(1), v(1) {} 192 constexpr S(const S &s) : i(2), v(2) {} 193 int i; 194 volatile int v; 195 }; 196 constexpr S s; 197 constexpr volatile S vs; // expected-note {{here}} 198 constexpr const volatile S &vrs = s; 199 static_assert(s.i, ""); 200 static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 201 static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 202 static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}} 203 static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 204 205 // - a non-volatile glvalue of literal type that refers to a non-volatile 206 // temporary object whose lifetime has not ended, initialized with a 207 // constant expression; 208 constexpr volatile S f() { return S(); } 209 static_assert(f().i, ""); // ok! there's no lvalue-to-rvalue conversion here! 210 static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{subexpression}} 211} 212 213// FIXME: 214// 215// DR1312: The proposed wording for this defect has issues, so we ignore this 216// bullet and instead prohibit casts from pointers to cv void (see core-20842 217// and core-20845). 218// 219// - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a 220// glvalue of type cv1 T that refers to an object of type cv2 U, where T and U 221// are neither the same type nor similar types (4.4 [conv.qual]); 222 223// FIXME: 224// - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that 225// refers to a non-active member of a union or a subobject thereof; 226 227// - an id-expression that refers to a variable or data member of reference type 228// unless the reference has a preceding initialization, initialized with a 229// constant expression; 230namespace References { 231 const int a = 2; 232 int &b = *const_cast<int*>(&a); 233 int c = 10; // expected-note 2 {{here}} 234 int &d = c; 235 constexpr int e = 42; 236 int &f = const_cast<int&>(e); 237 extern int &g; 238 constexpr int &h(); // expected-note 2{{here}} 239 int &i = h(); // expected-note {{here}} expected-note {{undefined function 'h' cannot be used in a constant expression}} 240 constexpr int &j() { return b; } 241 int &k = j(); 242 243 struct S { 244 int A : a; 245 int B : b; 246 int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 247 int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 248 int D2 : &d - &c + 1; 249 int E : e / 2; 250 int F : f - 11; 251 int G : g; // expected-error {{constant expression}} 252 int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}} 253 int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}} 254 int J : j(); 255 int K : k; 256 }; 257} 258 259// - a dynamic_cast (5.2.7); 260namespace DynamicCast { 261 struct S { int n; }; 262 constexpr S s { 16 }; 263 struct T { 264 int n : dynamic_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{dynamic_cast}} 265 }; 266} 267 268// - a reinterpret_cast (5.2.10); 269namespace ReinterpretCast { 270 struct S { int n; }; 271 constexpr S s { 16 }; 272 struct T { 273 int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 274 }; 275 struct U { 276 int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 277 }; 278} 279 280// - a pseudo-destructor call (5.2.4); 281namespace PseudoDtor { 282 int k; 283 typedef int I; 284 struct T { 285 int n : (k.~I(), 0); // expected-error {{constant expression}} expected-note{{subexpression}} 286 }; 287} 288 289// - increment or decrement operations (5.2.6, 5.3.2); 290namespace IncDec { 291 int k = 2; 292 struct T { 293 int n : ++k; // expected-error {{constant expression}} 294 int m : --k; // expected-error {{constant expression}} 295 }; 296} 297 298// - a typeid expression (5.2.8) whose operand is of a polymorphic class type; 299namespace std { 300 struct type_info { 301 virtual ~type_info(); 302 const char *name; 303 }; 304} 305namespace TypeId { 306 struct S { virtual void f(); }; 307 constexpr S *p = 0; 308 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'}} 309 310 struct T {} t; 311 constexpr const std::type_info &ti2 = typeid(t); 312} 313 314// - a new-expression (5.3.4); 315// - a delete-expression (5.3.5); 316namespace NewDelete { 317 int *p = 0; 318 struct T { 319 int n : *new int(4); // expected-error {{constant expression}} expected-note {{subexpression}} 320 int m : (delete p, 2); // expected-error {{constant expression}} expected-note {{subexpression}} 321 }; 322} 323 324// - a relational (5.9) or equality (5.10) operator where the result is 325// unspecified; 326namespace UnspecifiedRelations { 327 int a, b; 328 constexpr int *p = &a, *q = &b; 329 // C++11 [expr.rel]p2: If two pointers p and q of the same type point to 330 // different objects that are not members of the same array or to different 331 // functions, or if only one of them is null, the results of p<q, p>q, p<=q, 332 // and p>=q are unspecified. 333 constexpr bool u1 = p < q; // expected-error {{constant expression}} 334 constexpr bool u2 = p > q; // expected-error {{constant expression}} 335 constexpr bool u3 = p <= q; // expected-error {{constant expression}} 336 constexpr bool u4 = p >= q; // expected-error {{constant expression}} 337 constexpr bool u5 = p < 0; // expected-error {{constant expression}} 338 constexpr bool u6 = p <= 0; // expected-error {{constant expression}} 339 constexpr bool u7 = p > 0; // expected-error {{constant expression}} 340 constexpr bool u8 = p >= 0; // expected-error {{constant expression}} 341 constexpr bool u9 = 0 < q; // expected-error {{constant expression}} 342 constexpr bool u10 = 0 <= q; // expected-error {{constant expression}} 343 constexpr bool u11 = 0 > q; // expected-error {{constant expression}} 344 constexpr bool u12 = 0 >= q; // expected-error {{constant expression}} 345 void f(), g(); 346 347 constexpr void (*pf)() = &f, (*pg)() = &g; 348 constexpr bool u13 = pf < pg; // expected-error {{constant expression}} 349 constexpr bool u14 = pf == pg; 350 351 // FIXME: 352 // If two pointers point to non-static data members of the same object with 353 // different access control, the result is unspecified. 354 355 // FIXME: 356 // [expr.rel]p3: Pointers to void can be compared [...] if both pointers 357 // represent the same address or are both the null pointer [...]; otherwise 358 // the result is unspecified. 359 360 // FIXME: Implement comparisons of pointers to members. 361 // [expr.eq]p2: If either is a pointer to a virtual member function and 362 // neither is null, the result is unspecified. 363} 364 365// - an assignment or a compound assignment (5.17); or 366namespace Assignment { 367 int k; 368 struct T { 369 int n : (k = 9); // expected-error {{constant expression}} 370 int m : (k *= 2); // expected-error {{constant expression}} 371 }; 372 373 struct Literal { 374 constexpr Literal(const char *name) : name(name) {} 375 const char *name; 376 }; 377 struct Expr { 378 constexpr Expr(Literal l) : IsLiteral(true), l(l) {} 379 bool IsLiteral; 380 union { 381 Literal l; 382 // ... 383 }; 384 }; 385 struct MulEq { 386 constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {} 387 Expr LHS; 388 Expr RHS; 389 }; 390 constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); } 391 Literal a("a"); 392 Literal b("b"); 393 MulEq c = a *= b; // ok 394} 395 396// - a throw-expression (15.1) 397namespace Throw { 398 struct S { 399 int n : (throw "hello", 10); // expected-error {{constant expression}} expected-note {{subexpression}} 400 }; 401} 402 403// PR9999 404template<unsigned int v> 405class bitWidthHolding { 406public: 407 static const 408 unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1); 409}; 410 411static const int width=bitWidthHolding<255>::width; 412 413template<bool b> 414struct always_false { 415 static const bool value = false; 416}; 417 418template<bool b> 419struct and_or { 420 static const bool and_value = b && and_or<always_false<b>::value>::and_value; 421 static const bool or_value = !b || and_or<always_false<b>::value>::or_value; 422}; 423 424static const bool and_value = and_or<true>::and_value; 425static const bool or_value = and_or<true>::or_value; 426 427static_assert(and_value == false, ""); 428static_assert(or_value == true, ""); 429