// RUN: %clang_cc1 -fsyntax-only -std=c++11 -pedantic -verify=expected,cxx11 -fcxx-exceptions %s -fconstexpr-depth=128 -triple i686-pc-linux-gnu
// RUN: %clang_cc1 -fsyntax-only -std=c++2a -pedantic -verify=expected,cxx20 -fcxx-exceptions %s -fconstexpr-depth=128 -triple i686-pc-linux-gnu
// A conditional-expression is a core constant expression unless it involves one
// of the following as a potentially evaluated subexpression [...]:
// - this (5.1.1 [expr.prim.general]) [Note: when evaluating a constant
// expression, function invocation substitution (7.1.5 [dcl.constexpr])
// replaces each occurrence of this in a constexpr member function with a
// pointer to the class object. -end note];
struct This {
int this1 : this1; // expected-error {{undeclared}}
int this2 : this->this1; // expected-error {{invalid}}
void this3() {
int n1[this->this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
int n2[this1]; // expected-warning {{variable length array}} expected-note {{'this'}}
(void)n1, (void)n2;
}
};
// - an invocation of a function other than a constexpr constructor for a
// literal class or a constexpr function [ Note: Overload resolution (13.3)
// is applied as usual - end note ];
struct NonConstexpr1 {
static int f() { return 1; } // expected-note {{here}}
int n : f(); // expected-error {{constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
};
struct NonConstexpr2 {
constexpr NonConstexpr2(); // expected-note {{here}}
int n;
};
struct NonConstexpr3 {
NonConstexpr3();
int m : NonConstexpr2().n; // expected-error {{constant expression}} expected-note {{undefined constructor 'NonConstexpr2'}}
};
struct NonConstexpr4 {
NonConstexpr4();
int n;
};
struct NonConstexpr5 {
int n : NonConstexpr4().n; // expected-error {{constant expression}} expected-note {{non-literal type 'NonConstexpr4' cannot be used in a constant expression}}
};
// - an invocation of an undefined constexpr function or an undefined
// constexpr constructor;
struct UndefinedConstexpr {
constexpr UndefinedConstexpr();
static constexpr int undefinedConstexpr1(); // expected-note {{here}}
int undefinedConstexpr2 : undefinedConstexpr1(); // expected-error {{constant expression}} expected-note {{undefined function 'undefinedConstexpr1' cannot be used in a constant expression}}
};
// - an invocation of a constexpr function with arguments that, when substituted
// by function invocation substitution (7.1.5), do not produce a core constant
// expression;
namespace NonConstExprReturn {
static constexpr const int &id_ref(const int &n) {
return n;
}
struct NonConstExprFunction {
int n : id_ref(16); // ok
};
constexpr const int *address_of(const int &a) {
return &a;
}
constexpr const int *return_param(int n) {
return address_of(n);
}
struct S {
int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of object outside its lifetime}}
};
}
// - an invocation of a constexpr constructor with arguments that, when
// substituted by function invocation substitution (7.1.5), do not produce all
// constant expressions for the constructor calls and full-expressions in the
// mem-initializers (including conversions);
namespace NonConstExprCtor {
struct T {
constexpr T(const int &r) :
r(r) {
}
const int &r;
};
constexpr int n = 0;
constexpr T t1(n); // ok
constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{reference to temporary is not a constant expression}}
struct S {
int n : T(4).r; // ok
};
}
// - an invocation of a constexpr function or a constexpr constructor that would
// exceed the implementation-defined recursion limits (see Annex B);
namespace RecursionLimits {
constexpr int RecurseForever(int n) {
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}}
}
struct AlsoRecurseForever {
constexpr AlsoRecurseForever(int n) :
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}}
{}
int n;
};
struct S {
int k : RecurseForever(0); // expected-error {{constant expression}} expected-note {{in call to}}
int l : AlsoRecurseForever(0).n; // expected-error {{constant expression}} expected-note {{in call to}}
};
}
// DR1458: taking the address of an object of incomplete class type
namespace IncompleteClassTypeAddr {
struct S;
extern S s;
constexpr S *p = &s; // ok
static_assert(p, "");
extern S sArr[];
constexpr S (*p2)[] = &sArr; // ok
struct S {
constexpr S *operator&() const { return nullptr; }
};
constexpr S *q = &s; // ok
static_assert(!q, "");
}
// - an operation that would have undefined behavior [Note: including, for
// example, signed integer overflow (Clause 5 [expr]), certain pointer
// arithmetic (5.7 [expr.add]), division by zero (5.6 [expr.mul]), or certain
// shift operations (5.8 [expr.shift]) -end note];
namespace UndefinedBehavior {
void f(int n) {
switch (n) {
case (int)4.4e9: // expected-error {{constant expression}} expected-note {{value 4.4E+9 is outside the range of representable values of type 'int'}}
case (int)0x80000000u: // ok
case (int)10000000000ll: // expected-note {{here}}
case (unsigned int)10000000000ll: // expected-error {{duplicate case value}}
case (int)(unsigned)(long long)4.4e9: // ok
case (int)(float)1e300: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
case (int)((float)1e37 / 1e30): // ok
case (int)(__fp16)65536: // expected-error {{constant expression}} expected-note {{value +Inf is outside the range of representable values of type 'int'}}
break;
}
}
constexpr int int_min = ~0x7fffffff;
constexpr int minus_int_min = -int_min; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
constexpr int minus_int_min_from_shift = -(1<<31); // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
constexpr int div0 = 3 / 0; // expected-error {{constant expression}} expected-note {{division by zero}}
constexpr int mod0 = 3 % 0; // expected-error {{constant expression}} expected-note {{division by zero}}
constexpr int int_min_div_minus_1 = int_min / -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
constexpr int int_min_mod_minus_1 = int_min % -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range}}
constexpr int shl_m1 = 0 << -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
constexpr int shl_0 = 0 << 0; // ok
constexpr int shl_31 = 0 << 31; // ok
constexpr int shl_32 = 0 << 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type 'int' (32}}
constexpr int shl_unsigned_negative = unsigned(-3) << 1; // ok
constexpr int shl_unsigned_into_sign = 1u << 31; // ok
constexpr int shl_unsigned_overflow = 1024u << 31; // ok
constexpr int shl_signed_negative = (-3) << 1; // cxx11-error {{constant expression}} cxx11-note {{left shift of negative value -3}}
constexpr int shl_signed_ok = 1 << 30; // ok
constexpr int shl_signed_into_sign = 1 << 31; // ok (DR1457)
constexpr int shl_signed_into_sign_2 = 0x7fffffff << 1; // ok (DR1457)
constexpr int shl_signed_off_end = 2 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits}}
constexpr int shl_signed_off_end_2 = 0x7fffffff << 2; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{signed shift result (0x1FFFFFFFC) requires 34 bits to represent, but 'int' only has 32 bits}}
constexpr int shl_signed_overflow = 1024 << 31; // cxx11-error {{constant expression}} cxx11-note {{signed left shift discards bits}} cxx11-warning {{requires 43 bits to represent}}
constexpr int shl_signed_ok2 = 1024 << 20; // ok
constexpr int shr_m1 = 0 >> -1; // expected-error {{constant expression}} expected-note {{negative shift count -1}}
constexpr int shr_0 = 0 >> 0; // ok
constexpr int shr_31 = 0 >> 31; // ok
constexpr int shr_32 = 0 >> 32; // expected-error {{constant expression}} expected-note {{shift count 32 >= width of type}}
struct S {
int m;
};
constexpr S s = { 5 };
constexpr const int *p = &s.m + 1;
constexpr const int &f(const int *q) {
return q[0];
}
constexpr int n = (f(p), 0); // ok
struct T {
int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
};
namespace Ptr {
struct A {};
struct B : A { int n; };
B a[3][3];
constexpr B *p = a[0] + 4; // expected-error {{constant expression}} expected-note {{element 4 of array of 3 elements}}
B b = {};
constexpr A *pa = &b + 1; // expected-error {{constant expression}} expected-note {{base class of pointer past the end}}
constexpr B *pb = (B*)((A*)&b + 1); // expected-error {{constant expression}} expected-note {{derived class of pointer past the end}}
constexpr const int *pn = &(&b + 1)->n; // expected-error {{constant expression}} expected-note {{field of pointer past the end}}
constexpr B *parr = &a[3][0]; // expected-error {{constant expression}} expected-note {{array element of pointer past the end}}
constexpr A *na = nullptr;
constexpr B *nb = nullptr;
constexpr A &ra = *nb; // expected-error {{constant expression}} expected-note {{cannot access base class of null pointer}}
constexpr B &rb = (B&)*na; // expected-error {{constant expression}} expected-note {{cannot access derived class of null pointer}}
static_assert((A*)nb == 0, "");
static_assert((B*)na == 0, "");
constexpr const int &nf = nb->n; // expected-error {{constant expression}} expected-note {{cannot access field of null pointer}}
constexpr const int *np1 = (int*)nullptr + 0; // ok
constexpr const int *np2 = &(*(int(*)[4])nullptr)[0]; // ok
constexpr const int *np3 = &(*(int(*)[4])nullptr)[2]; // expected-error {{constant expression}} expected-note {{cannot perform pointer arithmetic on null pointer}}
struct C {
constexpr int f() const { return 0; }
} constexpr c = C();
constexpr int k1 = c.f(); // ok
constexpr int k2 = ((C*)nullptr)->f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced null pointer}}
constexpr int k3 = (&c)[1].f(); // expected-error {{constant expression}} expected-note {{member call on dereferenced one-past-the-end pointer}}
C c2;
constexpr int k4 = c2.f(); // ok!
constexpr int diff1 = &a[2] - &a[0];
constexpr int diff2 = &a[1][3] - &a[1][0];
constexpr int diff3 = &a[2][0] - &a[1][0]; // expected-error {{constant expression}} expected-note {{subtracted pointers are not elements of the same array}}
static_assert(&a[2][0] == &a[1][3], "");
constexpr int diff4 = (&b + 1) - &b;
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}}
constexpr int diff6 = &a[1][2].n - &a[1][2].n;
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}}
}
namespace Overflow {
// Signed int overflow.
constexpr int n1 = 2 * 3 * 3 * 7 * 11 * 31 * 151 * 331; // ok
constexpr int n2 = 65536 * 32768; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
constexpr int n3 = n1 + 1; // ok
constexpr int n4 = n3 + 1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
constexpr int n5 = -65536 * 32768; // ok
constexpr int n6 = 3 * -715827883; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
constexpr int n7 = -n3 + -1; // ok
constexpr int n8 = -1 + n7; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
constexpr int n9 = n3 - 0; // ok
constexpr int n10 = n3 - -1; // expected-error {{constant expression}} expected-note {{value 2147483648 is outside the range of }}
constexpr int n11 = -1 - n3; // ok
constexpr int n12 = -2 - n3; // expected-error {{constant expression}} expected-note {{value -2147483649 is outside the range of }}
constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
constexpr signed char c2 = '\x64' * '\2'; // also ok expected-warning{{changes value}}
constexpr long long ll1 = 0x7fffffffffffffff; // ok
constexpr long long ll2 = ll1 + 1; // expected-error {{constant}} expected-note {{ 9223372036854775808 }}
constexpr long long ll3 = -ll1 - 1; // ok
constexpr long long ll4 = ll3 - 1; // expected-error {{constant}} expected-note {{ -9223372036854775809 }}
constexpr long long ll5 = ll3 * ll3; // expected-error {{constant}} expected-note {{ 85070591730234615865843651857942052864 }}
// Yikes.
char melchizedek[2200000000];
typedef decltype(melchizedek[1] - melchizedek[0]) ptrdiff_t;
constexpr ptrdiff_t d1 = &melchizedek[0x7fffffff] - &melchizedek[0]; // ok
constexpr ptrdiff_t d2 = &melchizedek[0x80000000u] - &melchizedek[0]; // expected-error {{constant expression}} expected-note {{ 2147483648 }}
constexpr ptrdiff_t d3 = &melchizedek[0] - &melchizedek[0x80000000u]; // ok
constexpr ptrdiff_t d4 = &melchizedek[0] - &melchizedek[0x80000001u]; // expected-error {{constant expression}} expected-note {{ -2147483649 }}
// Unsigned int overflow.
static_assert(65536u * 65536u == 0u, ""); // ok
static_assert(4294967295u + 1u == 0u, ""); // ok
static_assert(0u - 1u == 4294967295u, ""); // ok
static_assert(~0u * ~0u == 1u, ""); // ok
template<typename T> constexpr bool isinf(T v) { return v && v / 2 == v; }
// Floating-point overflow and NaN.
constexpr float f1 = 1e38f * 3.4028f; // ok
constexpr float f2 = 1e38f * 3.4029f; // ok, +inf is in range of representable values
constexpr float f3 = 1e38f / -.2939f; // ok
constexpr float f4 = 1e38f / -.2938f; // ok, -inf is in range of representable values
constexpr float f5 = 2e38f + 2e38f; // ok, +inf is in range of representable values
constexpr float f6 = -2e38f - 2e38f; // ok, -inf is in range of representable values
constexpr float f7 = 0.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
constexpr float f8 = 1.f / 0.f; // expected-error {{constant expression}} expected-note {{division by zero}}
constexpr float f9 = 1e308 / 1e-308; // ok, +inf
constexpr float f10 = f2 - f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
constexpr float f11 = f2 + f4; // expected-error {{constant expression}} expected-note {{produces a NaN}}
constexpr float f12 = f2 / f2; // expected-error {{constant expression}} expected-note {{produces a NaN}}
#pragma float_control(push)
#pragma float_control(except, on)
constexpr float pi = 3.14f;
constexpr unsigned ubig = 0xFFFFFFFF;
constexpr float ce = 1.0 / 3.0; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
constexpr int ci = (int) pi;
constexpr float fbig = (float) ubig; // not-expected-error {{constant expression}} not-expected-note {{floating point arithmetic suppressed in strict evaluation modes}}
constexpr float fabspi = __builtin_fabs(pi); // no error expected
constexpr float negpi = -pi; // expect no error on unary operator
#pragma float_control(pop)
static_assert(!isinf(f1), "");
static_assert(isinf(f2), "");
static_assert(!isinf(f3), "");
static_assert(isinf(f4), "");
static_assert(isinf(f5), "");
static_assert(isinf(f6), "");
static_assert(isinf(f9), "");
}
#if __cplusplus >= 201703L
namespace CompoundAssignment {
constexpr int rem() { // expected-error {{constexpr function never produces a constant expression}}
int x = ~__INT_MAX__;
return x%=-1; // cxx20-note {{value 2147483648 is outside the range of representable values of type 'int'}}
}
}
#endif
}
// - a lambda-expression (5.1.2);
struct Lambda {
int n : []{ return 1; }(); // cxx11-error {{constant expression}} cxx11-error {{integral constant expression}} cxx11-note {{non-literal type}}
};
// - an lvalue-to-rvalue conversion (4.1) unless it is applied to
namespace LValueToRValue {
// - a non-volatile glvalue of integral or enumeration type that refers to a
// non-volatile const object with a preceding initialization, initialized
// with a constant expression [Note: a string literal (2.14.5 [lex.string])
// corresponds to an array of such objects. -end note], or
volatile const int vi = 1; // expected-note 2{{here}}
const int ci = 1;
volatile const int &vrci = ci;
static_assert(vi, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
static_assert(const_cast<int&>(vi), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
static_assert(vrci, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
// - a non-volatile glvalue of literal type that refers to a non-volatile
// object defined with constexpr, or that refers to a sub-object of such an
// object, or
struct V {
constexpr V() : v(1) {}
volatile int v; // expected-note {{not literal because}}
};
constexpr V v; // expected-error {{non-literal type}}
struct S {
constexpr S(int=0) : i(1), v(const_cast<volatile int&>(vi)) {}
constexpr S(const S &s) : i(2), v(const_cast<volatile int&>(vi)) {}
int i;
volatile int &v;
};
constexpr S s; // ok
constexpr volatile S vs; // expected-note {{here}}
constexpr const volatile S &vrs = s; // ok
static_assert(s.i, "");
static_assert(s.v, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
static_assert(const_cast<int&>(s.v), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vi'}}
static_assert(vs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
static_assert(const_cast<int&>(vs.i), ""); // expected-error {{constant expression}} expected-note {{read of volatile object 'vs'}}
static_assert(vrs.i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
// - a non-volatile glvalue of literal type that refers to a non-volatile
// temporary object whose lifetime has not ended, initialized with a
// constant expression;
constexpr volatile S f() { return S(); }
static_assert(f().i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
}
// DR1312: The proposed wording for this defect has issues, so we ignore this
// bullet and instead prohibit casts from pointers to cv void (see core-20842
// and core-20845).
//
// - an lvalue-to-rvalue conversion (4.1 [conv.lval]) that is applied to a
// glvalue of type cv1 T that refers to an object of type cv2 U, where T and U
// are neither the same type nor similar types (4.4 [conv.qual]);
// - an lvalue-to-rvalue conversion (4.1) that is applied to a glvalue that
// refers to a non-active member of a union or a subobject thereof;
namespace LValueToRValueUnion {
// test/SemaCXX/constant-expression-cxx11.cpp contains more thorough testing
// of this.
union U { int a, b; } constexpr u = U();
static_assert(u.a == 0, "");
constexpr const int *bp = &u.b;
constexpr int b = *bp; // expected-error {{constant expression}} expected-note {{read of member 'b' of union with active member 'a'}}
extern const U pu;
constexpr const int *pua = &pu.a;
constexpr const int *pub = &pu.b;
constexpr U pu = { .b = 1 }; // cxx11-warning {{C++20 extension}}
constexpr const int a2 = *pua; // expected-error {{constant expression}} expected-note {{read of member 'a' of union with active member 'b'}}
constexpr const int b2 = *pub; // ok
}
// - an id-expression that refers to a variable or data member of reference type
// unless the reference has a preceding initialization, initialized with a
// constant expression;
namespace References {
const int a = 2;
int &b = *const_cast<int*>(&a);
int c = 10; // expected-note 2 {{here}}
int &d = c;
constexpr int e = 42;
int &f = const_cast<int&>(e);
extern int &g; // expected-note {{here}}
constexpr int &h(); // expected-note {{here}}
int &i = h(); // expected-note {{here}}
constexpr int &j() { return b; }
int &k = j();
struct S {
int A : a;
int B : b;
int C : c; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
int D : d; // expected-error {{constant expression}} expected-note {{read of non-const variable 'c'}}
int D2 : &d - &c + 1;
int E : e / 2;
int F : f - 11;
int G : g; // expected-error {{constant expression}} expected-note {{initializer of 'g' is unknown}}
int H : h(); // expected-error {{constant expression}} expected-note {{undefined function 'h'}}
int I : i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
int J : j();
int K : k;
};
}
// - a dynamic_cast (5.2.7);
namespace DynamicCast {
struct S { int n; };
constexpr S s { 16 };
struct T {
int n : dynamic_cast<const S*>(&s)->n; // cxx11-warning {{constant expression}} cxx11-note {{dynamic_cast}}
};
}
// - a reinterpret_cast (5.2.10);
namespace ReinterpretCast {
struct S { int n; };
constexpr S s { 16 };
struct T {
int n : reinterpret_cast<const S*>(&s)->n; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
};
struct U {
int m : (long)(S*)6; // expected-warning {{constant expression}} expected-note {{reinterpret_cast}}
};
}
// - a pseudo-destructor call (5.2.4);
namespace PseudoDtor {
int k;
typedef int I;
struct T {
int n : (k.~I(), 1); // expected-error {{constant expression}} expected-note {{visible outside that expression}}
};
constexpr int f(int a = 1) { // cxx11-error {{constant expression}} expected-note {{destroying object 'a' whose lifetime has already ended}}
return (
a.~I(), // cxx11-note {{pseudo-destructor}}
0);
}
static_assert(f() == 0, ""); // expected-error {{constant expression}}
// This is OK in C++20: the union has no active member after the
// pseudo-destructor call, so the union destructor has no effect.
union U { int x; };
constexpr int g(U u = {1}) { // cxx11-error {{constant expression}}
return (
u.x.~I(), // cxx11-note 2{{pseudo-destructor}}
0);
}
static_assert(g() == 0, ""); // cxx11-error {{constant expression}} cxx11-note {{in call}}
}
// - increment or decrement operations (5.2.6, 5.3.2);
namespace IncDec {
int k = 2;
struct T {
int n : ++k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
int m : --k; // expected-error {{constant expression}} cxx20-note {{visible outside}}
};
}
// - a typeid expression (5.2.8) whose operand is of a polymorphic class type;
namespace std {
struct type_info {
virtual ~type_info();
const char *name;
};
}
namespace TypeId {
struct S { virtual void f(); };
constexpr S *p = 0;
constexpr const std::type_info &ti1 = typeid(*p); // expected-error {{must be initialized by a constant expression}} cxx11-note {{typeid applied to expression of polymorphic type 'S'}} cxx20-note {{dereferenced null pointer}}
struct T {} t;
constexpr const std::type_info &ti2 = typeid(t);
}
// - a new-expression (5.3.4);
// - a delete-expression (5.3.5);
namespace NewDelete {
constexpr int *p = 0;
struct T {
int n : *new int(4); // expected-warning {{constant expression}} cxx11-note {{until C++20}} cxx20-note {{was not deallocated}}
int m : (delete p, 2); // cxx11-warning {{constant expression}} cxx11-note {{until C++20}}
};
}
// - a relational (5.9) or equality (5.10) operator where the result is
// unspecified;
namespace UnspecifiedRelations {
int a, b;
constexpr int *p = &a, *q = &b;
// C++11 [expr.rel]p2: If two pointers p and q of the same type point to
// different objects that are not members of the same array or to different
// functions, or if only one of them is null, the results of p<q, p>q, p<=q,
// and p>=q are unspecified.
constexpr bool u1 = p < q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
constexpr bool u2 = p > q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
constexpr bool u3 = p <= q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
constexpr bool u4 = p >= q; // expected-error {{constant expression}} expected-note {{comparison between '&a' and '&b' has unspecified value}}
constexpr bool u5 = p < (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
constexpr bool u6 = p <= (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
constexpr bool u7 = p > (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
constexpr bool u8 = p >= (int*)0; // expected-error {{constant expression}} expected-note {{comparison between '&a' and 'nullptr' has unspecified value}}
constexpr bool u9 = (int*)0 < q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
constexpr bool u10 = (int*)0 <= q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
constexpr bool u11 = (int*)0 > q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
constexpr bool u12 = (int*)0 >= q; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&b' has unspecified value}}
void f(), g();
constexpr void (*pf)() = &f, (*pg)() = &g;
constexpr bool u13 = pf < pg; // expected-error {{constant expression}} expected-note {{comparison between '&f' and '&g' has unspecified value}}
// expected-warning@-1 {{ordered comparison of function pointers}}
constexpr bool u14 = pf == pg;
// If two pointers point to non-static data members of the same object with
// different access control, the result is unspecified.
struct A {
public:
constexpr A() : a(0), b(0) {}
int a;
constexpr bool cmp() const { return &a < &b; } // expected-note {{comparison of address of fields 'a' and 'b' of 'A' with differing access specifiers (public vs private) has unspecified value}}
private:
int b;
};
static_assert(A().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
class B {
public:
A a;
constexpr bool cmp() const { return &a.a < &b.a; } // expected-note {{comparison of address of fields 'a' and 'b' of 'B' with differing access specifiers (public vs protected) has unspecified value}}
protected:
A b;
};
static_assert(B().cmp(), ""); // expected-error {{constant expression}} expected-note {{in call}}
// If two pointers point to different base sub-objects of the same object, or
// one points to a base subobject and the other points to a member, the result
// of the comparison is unspecified. This is not explicitly called out by
// [expr.rel]p2, but is covered by 'Other pointer comparisons are
// unspecified'.
struct C {
int c[2];
};
struct D {
int d;
};
struct E : C, D {
struct Inner {
int f;
} e;
} e;
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}}
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}}
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}}
// [expr.rel]p3: Pointers to void can be compared [...] if both pointers
// represent the same address or are both the null pointer [...]; otherwise
// the result is unspecified.
// Same address restriction removed by CWG2749
struct S { int a, b; } s;
constexpr void *null = 0;
constexpr void *pv = (void*)&s.a;
constexpr void *qv = (void*)&s.b;
constexpr bool v1 = null < (int*)0;
constexpr bool v2 = null < pv; // expected-error {{constant expression}} expected-note {{comparison between 'nullptr' and '&s.a' has unspecified value}}
constexpr bool v3 = null == pv;
constexpr bool v4 = qv == pv;
constexpr bool v5 = qv >= pv;
constexpr bool v6 = qv > null; // expected-error {{constant expression}} expected-note {{comparison between '&s.b' and 'nullptr' has unspecified value}}
constexpr bool v7 = qv <= (void*)&s.b;
constexpr bool v8 = qv > (void*)&s.a;
}
// - an assignment or a compound assignment (5.17); or
namespace Assignment {
int k;
struct T {
int n : (k = 9); // expected-error {{constant expression}} cxx20-note {{visible outside}}
int m : (k *= 2); // expected-error {{constant expression}} cxx20-note {{visible outside}}
};
struct Literal {
constexpr Literal(const char *name) : name(name) {}
const char *name;
};
struct Expr {
constexpr Expr(Literal l) : IsLiteral(true), l(l) {}
bool IsLiteral;
union {
Literal l;
// ...
};
};
struct MulEq {
constexpr MulEq(Expr a, Expr b) : LHS(a), RHS(b) {}
Expr LHS;
Expr RHS;
};
constexpr MulEq operator*=(Expr a, Expr b) { return MulEq(a, b); }
Literal a("a");
Literal b("b");
MulEq c = a *= b; // ok
}
// - a throw-expression (15.1)
namespace Throw {
struct S {
int n : (throw "hello", 10); // expected-error {{constant expression}}
};
}
// PR9999
template<unsigned int v>
class bitWidthHolding {
public:
static const
unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
};
static const int width=bitWidthHolding<255>::width;
template<bool b>
struct always_false {
static const bool value = false;
};
template<bool b>
struct and_or {
static const bool and_value = b && and_or<always_false<b>::value>::and_value;
static const bool or_value = !b || and_or<always_false<b>::value>::or_value;
};
static const bool and_value = and_or<true>::and_value;
static const bool or_value = and_or<true>::or_value;
static_assert(and_value == false, "");
static_assert(or_value == true, "");
namespace rdar13090123 {
typedef __INTPTR_TYPE__ intptr_t;
constexpr intptr_t f(intptr_t x) {
return (((x) >> 21) * 8);
}
extern "C" int foo;
constexpr intptr_t i = f((intptr_t)&foo - 10); // expected-error{{constexpr variable 'i' must be initialized by a constant expression}} \
// expected-note{{reinterpret_cast}}
}
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