// RUN: %clang_cc1 -verify -std=c++11 -fcxx-exceptions -Werror=c++14-extensions -Werror=c++20-extensions %s
// RUN: %clang_cc1 -verify -std=c++14 -fcxx-exceptions -DCXX14 -Werror=c++20-extensions %s
// RUN: %clang_cc1 -verify -std=c++20 -fcxx-exceptions -DCXX14 -DCXX2A %s
namespace N {
typedef char C;
}
namespace M {
typedef double D;
}
struct NonLiteral { // expected-note 2{{no constexpr constructors}}
NonLiteral() {}
NonLiteral(int) {}
};
struct Literal {
constexpr Literal() {}
explicit Literal(int); // expected-note 2 {{here}}
operator int() const { return 0; }
};
// In the definition of a constexpr constructor, each of the parameter types
// shall be a literal type.
struct S {
constexpr S(int, N::C) {}
constexpr S(int, NonLiteral, N::C) {} // expected-error {{constexpr constructor's 2nd parameter type 'NonLiteral' is not a literal type}}
constexpr S(int, NonLiteral = 42) {} // expected-error {{constexpr constructor's 2nd parameter type 'NonLiteral' is not a literal type}}
// In addition, either its function-body shall be = delete or = default
constexpr S() = default;
constexpr S(Literal) = delete;
};
// or it shall satisfy the following constraints:
// - the class shall not have any virtual base classes;
struct T : virtual S { // expected-note {{here}}
constexpr T() {} // expected-error {{constexpr constructor not allowed in struct with virtual base class}}
};
namespace IndirectVBase {
struct A {};
struct B : virtual A {}; // expected-note {{here}}
class C : public B {
public:
constexpr C() {} // expected-error {{constexpr constructor not allowed in class with virtual base class}}
};
}
// - its function-body shall not be a function-try-block;
struct U {
constexpr U()
try
#ifndef CXX2A
// expected-error@-2 {{function try block in constexpr constructor is a C++20 extension}}
#endif
: u() {
#ifndef CXX14
// expected-error@-2 {{use of this statement in a constexpr constructor is a C++14 extension}}
#endif
} catch (...) {
throw;
}
int u;
};
// - the compound-statememt of its function-body shall contain only
struct V {
constexpr V() {
// - null statements,
;
// - static_assert-declarations,
static_assert(true, "the impossible happened!");
// - typedef declarations and alias-declarations that do not define classes
// or enumerations,
typedef int I;
typedef struct S T;
using J = int;
using K = int[sizeof(I) + sizeof(J)];
// Note, the standard requires we reject this.
struct U;
// - using-declarations,
using N::C;
// - and using-directives;
using namespace N;
}
constexpr V(int(&)[1]) {
for (int n = 0; n < 10; ++n)
/**/;
#ifndef CXX14
// expected-error@-3 {{statement not allowed in constexpr constructor}}
#endif
}
constexpr V(int(&)[2]) {
constexpr int a = 0;
#ifndef CXX14
// expected-error@-2 {{variable declaration in a constexpr constructor is a C++14 extension}}
#endif
}
constexpr V(int(&)[3]) {
constexpr int ForwardDecl(int);
#ifndef CXX14
// expected-error@-2 {{use of this statement in a constexpr constructor is a C++14 extension}}
#endif
}
constexpr V(int(&)[4]) {
typedef struct { } S1;
#ifndef CXX14
// expected-error@-2 {{type definition in a constexpr constructor is a C++14 extension}}
#endif
}
constexpr V(int(&)[5]) {
using S2 = struct { };
#ifndef CXX14
// expected-error@-2 {{type definition in a constexpr constructor is a C++14 extension}}
#endif
}
constexpr V(int(&)[6]) {
struct S3 { };
#ifndef CXX14
// expected-error@-2 {{type definition in a constexpr constructor is a C++14 extension}}
#endif
}
constexpr V(int(&)[7]) {
return;
#ifndef CXX14
// expected-error@-2 {{use of this statement in a constexpr constructor is a C++14 extension}}
#endif
}
};
// - every non-static data member and base class sub-object shall be initialized
struct W {
int n;
constexpr W() {}
#ifndef CXX2A
// expected-error@-2 {{constexpr constructor that does not initialize all members}}
// expected-note@-4 {{member not initialized by constructor}}
#endif
};
struct AnonMembers {
int a; // expected-note 0-1{{member not initialized by constructor}}
union { // expected-note 0-2{{member not initialized by constructor}}
char b;
struct {
double c;
long d; // expected-note 0-1{{member not initialized by constructor}}
};
union {
char e;
void *f;
};
};
struct { // expected-note 0-1{{member not initialized by constructor}}
long long g;
struct {
int h; // expected-note 0-1{{member not initialized by constructor}}
double i; // expected-note 0-1{{member not initialized by constructor}}
};
union { // expected-note 0-2{{member not initialized by constructor}}
char *j;
AnonMembers *k;
};
};
constexpr AnonMembers(int(&)[1]) : a(), b(), g(), h(), i(), j() {} // ok
// missing d, i, j/k union
constexpr AnonMembers(int(&)[2]) : a(), c(), g(), h() {}
#ifndef CXX2A
// expected-error@-2 {{constexpr constructor that does not initialize all members}}
#endif
constexpr AnonMembers(int(&)[3]) : a(), e(), g(), h(), i(), k() {} // ok
// missing h, j/k union
constexpr AnonMembers(int(&)[4]) : a(), c(), d(), g(), i() {}
#ifndef CXX2A
// expected-error@-2 {{constexpr constructor that does not initialize all members}}
#endif
// missing b/c/d/e/f union
constexpr AnonMembers(int(&)[5]) : a(), g(), h(), i(), k() {}
#ifndef CXX2A
// expected-error@-2 {{constexpr constructor that does not initialize all members}}
#endif
// missing a, b/c/d/e/f union, g/h/i/j/k struct
constexpr AnonMembers(int(&)[6]) {}
#ifndef CXX2A
// expected-error@-2 {{constexpr constructor that does not initialize all members}}
#endif
};
union Empty {
constexpr Empty() {} // ok
} constexpr empty1;
struct EmptyVariant {
union {}; // expected-warning {{does not declare anything}}
struct {}; // expected-warning {{does not declare anything}}
constexpr EmptyVariant() {} // ok
} constexpr empty2;
template<typename T> using Int = int;
template<typename T>
struct TemplateInit {
T a;
int b; // desired-note {{not initialized}}
Int<T> c; // desired-note {{not initialized}}
struct {
T d;
int e; // desired-note {{not initialized}}
Int<T> f; // desired-note {{not initialized}}
};
struct {
Literal l;
Literal m;
Literal n[3];
};
union { // desired-note {{not initialized}}
T g;
T h;
};
// FIXME: This is ill-formed (no diagnostic required). We should diagnose it.
constexpr TemplateInit() {} // desired-error {{must initialize all members}}
};
template<typename T> struct TemplateInit2 {
Literal l;
constexpr TemplateInit2() {} // ok
};
template<typename T> struct weak_ptr {
constexpr weak_ptr() : p(0) {}
T *p;
};
template<typename T> struct enable_shared_from_this {
weak_ptr<T> weak_this;
constexpr enable_shared_from_this() {} // ok
};
constexpr int f(enable_shared_from_this<int>);
// - every constructor involved in initializing non-static data members and base
// class sub-objects shall be a constexpr constructor.
// This will no longer be the case once we support P2448R2
struct ConstexprBaseMemberCtors : Literal {
Literal l;
constexpr ConstexprBaseMemberCtors() : Literal(), l() {} // ok
constexpr ConstexprBaseMemberCtors(char) : // expected-error {{constexpr constructor never produces a constant expression}}
Literal(0), // expected-note {{non-constexpr constructor}}
l() {}
constexpr ConstexprBaseMemberCtors(double) : Literal(), // expected-error {{constexpr constructor never produces a constant expression}}
l(0) // expected-note {{non-constexpr constructor}}
{}
};
// - every assignment-expression that is an initializer-clause appearing
// directly or indirectly within a brace-or-equal-initializer for a non-static
// data member that is not named by a mem-initializer-id shall be a constant
// expression; and
//
// Note, we deliberately do not implement this bullet, so that we can allow the
// following example. (See N3308).
struct X {
int a = 0;
int b = 2 * a + 1; // ok, not a constant expression.
constexpr X() {}
constexpr X(int c) : a(c) {} // ok, b initialized by 2 * c + 1
};
union XU1 { int a; constexpr XU1() = default; };
#ifndef CXX2A
// expected-error@-2{{cannot be marked constexpr}}
#endif
union XU2 { int a = 1; constexpr XU2() = default; };
struct XU3 {
union {
int a;
};
constexpr XU3() = default;
#ifndef CXX2A
// expected-error@-2{{cannot be marked constexpr}}
#endif
};
struct XU4 {
union {
int a = 1;
};
constexpr XU4() = default;
};
static_assert(XU2().a == 1, "");
static_assert(XU4().a == 1, "");
// - every implicit conversion used in converting a constructor argument to the
// corresponding parameter type and converting a full-expression to the
// corresponding member type shall be one of those allowed in a constant
// expression.
//
// We implement the proposed resolution of DR1364 and ignore this bullet.
// However, we implement the intent of this wording as part of the p5 check that
// the function must be able to produce a constant expression.
int kGlobal; // expected-note {{here}}
struct Z {
constexpr Z(int a) : n(a) {}
constexpr Z() : n(kGlobal) {} // expected-error {{constexpr constructor never produces a constant expression}} expected-note {{read of non-const}}
int n;
};
namespace StdExample {
struct Length {
explicit constexpr Length(int i = 0) : val(i) { }
private:
int val;
};
}
namespace CtorLookup {
// Ensure that we look up which constructor will actually be used.
struct A {
constexpr A(const A&) {}
A(A&) {}
constexpr A(int = 0);
};
struct B : A {
B() = default;
constexpr B(const B&);
constexpr B(B&);
};
constexpr B::B(const B&) = default;
constexpr B::B(B&) = default; // expected-error {{cannot be marked constexpr}}
struct C {
A a;
C() = default;
constexpr C(const C&);
constexpr C(C&);
};
constexpr C::C(const C&) = default;
constexpr C::C(C&) = default; // expected-error {{cannot be marked constexpr}}
}
namespace PR14503 {
template<typename> struct V {
union {
int n;
struct {
int x,
y; // expected-note {{subobject declared here}}
};
};
constexpr V() : x(0) {}
};
// The constructor is still 'constexpr' here, but the result is not intended
// to be a constant expression. The standard is not clear on how this should
// work.
constexpr V<int> v; // expected-error {{constant expression}} expected-note {{subobject 'y' is not initialized}}
constexpr int k = V<int>().x; // FIXME: ok?
}
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