p2-0x.cpp revision 86c3ae46250cdcc57778c27826060779a92f3815
1// RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify -fcxx-exceptions %s -fconstexpr-depth 128 -triple i686-pc-linux-gnu 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// DR1458: taking the address of an object of incomplete class type 113namespace IncompleteClassTypeAddr { 114 struct S; 115 extern S s; 116 constexpr S *p = &s; // ok 117 static_assert(p, ""); 118 119 extern S sArr[]; 120 constexpr S (*p2)[] = &sArr; // ok 121 122 struct S { 123 constexpr S *operator&() { return nullptr; } 124 }; 125 constexpr S *q = &s; // ok 126 static_assert(!q, ""); 127} 128 129// - an operation that would have undefined behavior [Note: including, for 130// example, signed integer overflow (Clause 5 [expr]), certain pointer 131// arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain 132// shift operations (5.8 [expr.shift]) -end note]; 133namespace UndefinedBehavior { 134 void f(int n) { 135 switch (n) { 136 case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}} 137 case (int)0x80000000u: // ok 138 case (int)10000000000ll: // expected-note {{here}} 139 case (unsigned int)10000000000ll: // expected-error {{duplicate case value}} 140 case (int)(unsigned)(long long)4.4e9: // ok 141 case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value 1.0E+300 is outside the range of representable values of type 'float'}} 142 case (int)((float)1e37 / 1e30): // ok 143 case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value 65536 is outside the range of representable values of type 'half'}} 144 break; 145 } 146 } 147 148 constexpr int int_min = ~0x7fffffff; 149 constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 150 constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}} 151 constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}} expected-warning {{undefined}} 152 constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 153 constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}} 154 155 constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}} 156 constexpr int shl_0 = 0 << 0; // ok 157 constexpr int shl_31 = 0 << 31; // ok 158 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}} 159 constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok 160 constexpr int shl_unsigned_into_sign = 1u << 31; // ok 161 constexpr int shl_unsigned_overflow = 1024u << 31; // ok 162 constexpr int shl_signed_negative = (-3) << 1; // expected-error {{constant expression}} expected-note {{left shift of negative value -3}} 163 constexpr int shl_signed_ok = 1 << 30; // ok 164 constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457) 165 constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457) 166 constexpr int shl_signed_off_end = 2 << 31; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}} 167 constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}} 168 constexpr int shl_signed_overflow = 1024 << 31; // expected-error {{constant expression}} expected-note {{signed left shift discards bits}} expected-warning {{requires 43 bits to represent}} 169 constexpr int shl_signed_ok2 = 1024 << 20; // ok 170 171 constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}} expected-warning {{negative}} 172 constexpr int shr_0 = 0 >> 0; // ok 173 constexpr int shr_31 = 0 >> 31; // ok 174 constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}} expected-warning {{>= width of type}} 175 176 struct S { 177 int m; 178 }; 179 constexpr S s = { 5 }; // expected-note {{declared here}} 180 constexpr const int *p = &s.m + 1; 181 constexpr const int &f(const int *q) { 182 return q[0]; // expected-note {{dereferenced pointer past the end of subobject of 's' is not a constant expression}} 183 } 184 constexpr int n = (f(p), 0); // expected-error {{constant expression}} expected-note {{in call to 'f(&s.m + 1)'}} 185 struct T { 186 int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}} 187 }; 188 189 namespace Ptr { 190 struct A {}; 191 struct B : A { int n; }; 192 B a[3][3]; 193 constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}} 194 B b = {}; 195 constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}} 196 constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}} 197 constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}} 198 constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}} 199 200 constexpr A *na = nullptr; 201 constexpr B *nb = nullptr; 202 constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}} 203 constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}} 204 static_assert((A*)nb == 0, ""); 205 static_assert((B*)na == 0, ""); 206 constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}} 207 constexpr const int &np = (*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot access array element of null pointer}} 208 209 struct C { 210 constexpr int f() { return 0; } 211 } constexpr c = C(); 212 constexpr int k1 = c.f(); // ok 213 constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{cannot call member function on null pointer}} 214 constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{cannot call member function on pointer past the end of object}} 215 C c2; 216 constexpr int k4 = c2.f(); // ok! 217 218 constexpr int diff1 = &a[2] - &a[0]; 219 constexpr int diff2 = &a[1][3] - &a[1][0]; 220 constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}} 221 static_assert(&a[2][0] == &a[1][3], ""); 222 constexpr int diff4 = (&b + 1) - &b; 223 constexpr int diff5 = &a[1][2].n - &a[1][0].n; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}} 224 constexpr int diff6 = &a[1][2].n - &a[1][2].n; 225 constexpr int diff7 = (A*)&a[0][1] - (A*)&a[0][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}} 226 } 227 228 namespace Overflow { 229 // Signed int overflow. 230 constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok 231 constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }} 232 constexpr int n3 = n1 + 1; // ok 233 constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }} 234 constexpr int n5 = -65536 * 32768; // ok 235 constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }} 236 constexpr int n7 = -n3 + -1; // ok 237 constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }} 238 constexpr int n9 = n3 - 0; // ok 239 constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }} 240 constexpr int n11 = -1 - n3; // ok 241 constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }} 242 constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }} 243 constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }} 244 constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }} 245 constexpr signed char c1 = 100 * 2; // ok 246 constexpr signed char c2 = '\x64' * '\2'; // also ok 247 constexpr long long ll1 = 0x7fffffffffffffff; // ok 248 constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }} 249 constexpr long long ll3 = -ll1 - 1; // ok 250 constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }} 251 constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }} 252 253 // Yikes. 254 char melchizedek[2200000000]; 255 typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t; 256 constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok 257 constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }} 258 constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok 259 constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }} 260 261 // Unsigned int overflow. 262 static_assert(65536u * 65536u == 0u, ""); // ok 263 static_assert(4294967295u + 1u == 0u, ""); // ok 264 static_assert(0u - 1u == 4294967295u, ""); // ok 265 static_assert(~0u * ~0u == 1u, ""); // ok 266 267 // Floating-point overflow and NaN. 268 constexpr float f1 = 1e38f * 3.4028f; // ok 269 constexpr float f2 = 1e38f * 3.4029f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}} 270 constexpr float f3 = 1e38f / -.2939f; // ok 271 constexpr float f4 = 1e38f / -.2938f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}} 272 constexpr float f5 = 2e38f + 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}} 273 constexpr float f6 = -2e38f - 2e38f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces an infinity}} 274 constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{floating point arithmetic produces a NaN}} 275 } 276} 277 278// - a lambda-expression (5.1.2); 279struct Lambda { 280 // FIXME: clang crashes when trying to parse this! Revisit this check once 281 // lambdas are fully implemented. 282 //int n : []{ return 1; }(); 283}; 284 285// - an lvalue-to-rvalue conversion (4.1) unless it is applied to 286namespace LValueToRValue { 287 // - a non-volatile glvalue of integral or enumeration type that refers to a 288 // non-volatile const object with a preceding initialization, initialized 289 // with a constant expression [Note: a string literal (2.14.5 [lex.string]) 290 // corresponds to an array of such objects. -end note], or 291 volatile const int vi = 1; // expected-note 2{{here}} 292 const int ci = 1; 293 volatile const int &vrci = ci; 294 static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 295 static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}} 296 static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 297 298 // - a non-volatile glvalue of literal type that refers to a non-volatile 299 // object defined with constexpr, or that refers to a sub-object of such an 300 // object, or 301 struct V { 302 constexpr V() : v(1) {} 303 volatile int v; // expected-note {{not literal because}} 304 }; 305 constexpr V v; // expected-error {{non-literal type}} 306 struct S { 307 constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {} 308 constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {} 309 int i; 310 volatile int &v; 311 }; 312 constexpr S s; // ok 313 constexpr volatile S vs; // expected-note {{here}} 314 constexpr const volatile S &vrs = s; // ok 315 static_assert(s.i, ""); 316 static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 317 static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}} 318 static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 319 static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}} 320 static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}} 321 322 // - a non-volatile glvalue of literal type that refers to a non-volatile 323 // temporary object whose lifetime has not ended, initialized with a 324 // constant expression; 325 constexpr volatile S f() { return S(); } 326 static_assert(f().i, ""); // ok! there's no lvalue-to-rvalue conversion here! 327 static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} 328} 329 330// DR1312: The proposed wording for this defect has issues, so we ignore this 331// bullet and instead prohibit casts from pointers to cv void (see core-20842 332// and core-20845). 333// 334// - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a 335// glvalue of type cv1 T that refers to an object of type cv2 U, where T and U 336// are neither the same type nor similar types (4.4 [conv.qual]); 337 338// - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that 339// refers to a non-active member of a union or a subobject thereof; 340namespace LValueToRValueUnion { 341 // test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing 342 // of this. 343 union U { int a, b; } constexpr u = U(); 344 static_assert(u.a == 0, ""); 345 constexpr const int *bp = &u.b; 346 constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}} 347 348 extern const U pu; 349 constexpr const int *pua = &pu.a; 350 constexpr const int *pub = &pu.b; 351 constexpr U pu = { .b = 1 }; // expected-warning {{C99 feature}} 352 constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}} 353 constexpr const int b2 = *pub; // ok 354} 355 356// - an id-expression that refers to a variable or data member of reference type 357// unless the reference has a preceding initialization, initialized with a 358// constant expression; 359namespace References { 360 const int a = 2; 361 int &b = *const_cast<int*>(&a); 362 int c = 10; // expected-note 2 {{here}} 363 int &d = c; 364 constexpr int e = 42; 365 int &f = const_cast<int&>(e); 366 extern int &g; 367 constexpr int &h(); // expected-note 2{{here}} 368 int &i = h(); // expected-note {{here}} expected-note {{undefined function 'h' cannot be used in a constant expression}} 369 constexpr int &j() { return b; } 370 int &k = j(); 371 372 struct S { 373 int A : a; 374 int B : b; 375 int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 376 int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}} 377 int D2 : &d - &c + 1; 378 int E : e / 2; 379 int F : f - 11; 380 int G : g; // expected-error {{constant expression}} 381 int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}} 382 int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}} 383 int J : j(); 384 int K : k; 385 }; 386} 387 388// - a dynamic_cast (5.2.7); 389namespace DynamicCast { 390 struct S { int n; }; 391 constexpr S s { 16 }; 392 struct T { 393 int n : dynamic_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{dynamic_cast}} 394 }; 395} 396 397// - a reinterpret_cast (5.2.10); 398namespace ReinterpretCast { 399 struct S { int n; }; 400 constexpr S s { 16 }; 401 struct T { 402 int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 403 }; 404 struct U { 405 int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}} 406 }; 407} 408 409// - a pseudo-destructor call (5.2.4); 410namespace PseudoDtor { 411 int k; 412 typedef int I; 413 struct T { 414 int n : (k.~I(), 0); // expected-error {{constant expression}} 415 }; 416} 417 418// - increment or decrement operations (5.2.6, 5.3.2); 419namespace IncDec { 420 int k = 2; 421 struct T { 422 int n : ++k; // expected-error {{constant expression}} 423 int m : --k; // expected-error {{constant expression}} 424 }; 425} 426 427// - a typeid expression (5.2.8) whose operand is of a polymorphic class type; 428namespace std { 429 struct type_info { 430 virtual ~type_info(); 431 const char *name; 432 }; 433} 434namespace TypeId { 435 struct S { virtual void f(); }; 436 constexpr S *p = 0; 437 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'}} 438 439 struct T {} t; 440 constexpr const std::type_info &ti2 = typeid(t); 441} 442 443// - a new-expression (5.3.4); 444// - a delete-expression (5.3.5); 445namespace NewDelete { 446 int *p = 0; 447 struct T { 448 int n : *new int(4); // expected-error {{constant expression}} 449 int m : (delete p, 2); // expected-error {{constant expression}} 450 }; 451} 452 453// - a relational (5.9) or equality (5.10) operator where the result is 454// unspecified; 455namespace UnspecifiedRelations { 456 int a, b; 457 constexpr int *p = &a, *q = &b; 458 // C++11 [expr.rel]p2: If two pointers p and q of the same type point to 459 // different objects that are not members of the same array or to different 460 // functions, or if only one of them is null, the results of p<q, p>q, p<=q, 461 // and p>=q are unspecified. 462 constexpr bool u1 = p < q; // expected-error {{constant expression}} 463 constexpr bool u2 = p > q; // expected-error {{constant expression}} 464 constexpr bool u3 = p <= q; // expected-error {{constant expression}} 465 constexpr bool u4 = p >= q; // expected-error {{constant expression}} 466 constexpr bool u5 = p < 0; // expected-error {{constant expression}} 467 constexpr bool u6 = p <= 0; // expected-error {{constant expression}} 468 constexpr bool u7 = p > 0; // expected-error {{constant expression}} 469 constexpr bool u8 = p >= 0; // expected-error {{constant expression}} 470 constexpr bool u9 = 0 < q; // expected-error {{constant expression}} 471 constexpr bool u10 = 0 <= q; // expected-error {{constant expression}} 472 constexpr bool u11 = 0 > q; // expected-error {{constant expression}} 473 constexpr bool u12 = 0 >= q; // expected-error {{constant expression}} 474 void f(), g(); 475 476 constexpr void (*pf)() = &f, (*pg)() = &g; 477 constexpr bool u13 = pf < pg; // expected-error {{constant expression}} 478 constexpr bool u14 = pf == pg; 479 480 // If two pointers point to non-static data members of the same object with 481 // different access control, the result is unspecified. 482 struct A { 483 public: 484 constexpr A() : a(0), b(0) {} 485 int a; 486 constexpr bool cmp() { return &a < &b; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{comparison of address of fields 'a' and 'b' of 'A' with differing access specifiers (public vs private) has unspecified value}} 487 private: 488 int b; 489 }; 490 class B { 491 public: 492 A a; 493 constexpr bool cmp() { return &a.a < &b.a; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{comparison of address of fields 'a' and 'b' of 'B' with differing access specifiers (public vs protected) has unspecified value}} 494 protected: 495 A b; 496 }; 497 498 // If two pointers point to different base sub-objects of the same object, or 499 // one points to a base subobject and the other points to a member, the result 500 // of the comparison is unspecified. This is not explicitly called out by 501 // [expr.rel]p2, but is covered by 'Other pointer comparisons are 502 // unspecified'. 503 struct C { 504 int c[2]; 505 }; 506 struct D { 507 int d; 508 }; 509 struct E : C, D { 510 struct Inner { 511 int f; 512 } e; 513 } e; 514 constexpr bool base1 = &e.c[0] < &e.d; // expected-error {{constant expression}} expected-note {{comparison of addresses of subobjects of different base classes has unspecified value}} 515 constexpr bool base2 = &e.c[1] < &e.e.f; // expected-error {{constant expression}} expected-note {{comparison of address of base class subobject 'C' of class 'E' to field 'e' has unspecified value}} 516 constexpr bool base3 = &e.e.f < &e.d; // expected-error {{constant expression}} expected-note {{comparison of address of base class subobject 'D' of class 'E' to field 'e' has unspecified value}} 517 518 // [expr.rel]p3: Pointers to void can be compared [...] if both pointers 519 // represent the same address or are both the null pointer [...]; otherwise 520 // the result is unspecified. 521 struct S { int a, b; } s; 522 constexpr void *null = 0; 523 constexpr void *pv = (void*)&s.a; 524 constexpr void *qv = (void*)&s.b; 525 constexpr bool v1 = null < 0; 526 constexpr bool v2 = null < pv; // expected-error {{constant expression}} 527 constexpr bool v3 = null == pv; // ok 528 constexpr bool v4 = qv == pv; // ok 529 constexpr bool v5 = qv >= pv; // expected-error {{constant expression}} expected-note {{unequal pointers to void}} 530 constexpr bool v6 = qv > null; // expected-error {{constant expression}} 531 constexpr bool v7 = qv <= (void*)&s.b; // ok 532 constexpr bool v8 = qv > (void*)&s.a; // expected-error {{constant expression}} expected-note {{unequal pointers to void}} 533} 534 535// - an assignment or a compound assignment (5.17); or 536namespace Assignment { 537 int k; 538 struct T { 539 int n : (k = 9); // expected-error {{constant expression}} 540 int m : (k *= 2); // expected-error {{constant expression}} 541 }; 542 543 struct Literal { 544 constexpr Literal(const char *name) : name(name) {} 545 const char *name; 546 }; 547 struct Expr { 548 constexpr Expr(Literal l) : IsLiteral(true), l(l) {} 549 bool IsLiteral; 550 union { 551 Literal l; 552 // ... 553 }; 554 }; 555 struct MulEq { 556 constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {} 557 Expr LHS; 558 Expr RHS; 559 }; 560 constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); } 561 Literal a("a"); 562 Literal b("b"); 563 MulEq c = a *= b; // ok 564} 565 566// - a throw-expression (15.1) 567namespace Throw { 568 struct S { 569 int n : (throw "hello", 10); // expected-error {{constant expression}} 570 }; 571} 572 573// PR9999 574template<unsigned int v> 575class bitWidthHolding { 576public: 577 static const 578 unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1); 579}; 580 581static const int width=bitWidthHolding<255>::width; 582 583template<bool b> 584struct always_false { 585 static const bool value = false; 586}; 587 588template<bool b> 589struct and_or { 590 static const bool and_value = b && and_or<always_false<b>::value>::and_value; 591 static const bool or_value = !b || and_or<always_false<b>::value>::or_value; 592}; 593 594static const bool and_value = and_or<true>::and_value; 595static const bool or_value = and_or<true>::or_value; 596 597static_assert(and_value == false, ""); 598static_assert(or_value == true, ""); 599