// RUN: %clang_cc1 -triple %itanium_abi_triple -fsyntax-only -verify -std=c++11 %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -fsyntax-only -verify -std=c++14 %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -fsyntax-only -verify -std=c++17 %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -fsyntax-only -verify -std=c++2a %s
// MSVC always adopted the C++17 rule that implies that constexpr variables are
// implicitly inline, so do the test again.
// RUN: %clang_cc1 -triple x86_64-windows-msvc -DMS_ABI -fsyntax-only -verify -std=c++11 %s
struct notlit { // expected-note {{not literal because}}
notlit() {}
};
struct notlit2 {
notlit2() {}
};
// valid declarations
constexpr int i1 = 0;
constexpr int f1() { return 0; }
struct s1 {
constexpr static int mi1 = 0;
const static int mi2;
};
constexpr int s1::mi2 = 0;
// invalid declarations
// not a definition of an object
constexpr extern int i2; // expected-error {{constexpr variable declaration must be a definition}}
// not a literal type
constexpr notlit nl1; // expected-error {{constexpr variable cannot have non-literal type 'const notlit'}}
// function parameters
void f2(constexpr int i) {} // expected-error {{function parameter cannot be constexpr}}
// non-static member
struct s2 {
constexpr int mi1; // expected-error {{non-static data member cannot be constexpr; did you intend to make it const?}}
static constexpr int mi2;
#if __cplusplus <= 201402L && !defined(MS_ABI)
// expected-error@-2 {{requires an initializer}}
#else
// expected-error@-4 {{constexpr variable 'mi2' must be initialized by a constant expression}}
#endif
mutable constexpr int mi3 = 3; // expected-error-re {{non-static data member cannot be constexpr{{$}}}} expected-error {{'mutable' and 'const' cannot be mixed}}
};
// typedef
typedef constexpr int CI; // expected-error {{typedef cannot be constexpr}}
// tag
constexpr class C1 {}; // expected-error {{class cannot be marked constexpr}}
constexpr struct S1 {}; // expected-error {{struct cannot be marked constexpr}}
constexpr union U1 {}; // expected-error {{union cannot be marked constexpr}}
constexpr enum E1 {}; // expected-error {{enum cannot be marked constexpr}}
template <typename T> constexpr class TC1 {}; // expected-error {{class cannot be marked constexpr}}
template <typename T> constexpr struct TS1 {}; // expected-error {{struct cannot be marked constexpr}}
template <typename T> constexpr union TU1 {}; // expected-error {{union cannot be marked constexpr}}
class C2 {} constexpr; // expected-error {{class cannot be marked constexpr}}
struct S2 {} constexpr; // expected-error {{struct cannot be marked constexpr}}
union U2 {} constexpr; // expected-error {{union cannot be marked constexpr}}
enum E2 {} constexpr; // expected-error {{enum cannot be marked constexpr}}
constexpr class C3 {} c3 = C3();
constexpr struct S3 {} s3 = S3();
constexpr union U3 {} u3 = {};
constexpr enum E3 { V3 } e3 = V3;
class C4 {} constexpr c4 = C4();
struct S4 {} constexpr s4 = S4();
union U4 {} constexpr u4 = {};
enum E4 { V4 } constexpr e4 = V4;
constexpr int; // expected-error {{constexpr can only be used in variable and function declarations}}
// redeclaration mismatch
constexpr int f3(); // expected-note {{previous declaration is here}}
int f3(); // expected-error {{non-constexpr declaration of 'f3' follows constexpr declaration}}
int f4(); // expected-note {{previous declaration is here}}
constexpr int f4(); // expected-error {{constexpr declaration of 'f4' follows non-constexpr declaration}}
template<typename T> constexpr T f5(T);
template<typename T> constexpr T f5(T); // expected-note {{previous}}
template<typename T> T f5(T); // expected-error {{non-constexpr declaration of 'f5' follows constexpr declaration}}
template<typename T> T f6(T); // expected-note {{here}}
template<typename T> constexpr T f6(T); // expected-error {{constexpr declaration of 'f6' follows non-constexpr declaration}}
// destructor
struct ConstexprDtor {
constexpr ~ConstexprDtor() = default;
#if __cplusplus <= 201703L
// expected-error@-2 {{destructor cannot be declared constexpr}}
#endif
};
// template stuff
template <typename T> constexpr T ft(T t) { return t; }
template <typename T> T gt(T t) { return t; }
struct S {
template<typename T> constexpr T f(); // expected-warning 0-1{{C++14}} expected-note 0-1{{candidate}}
template <typename T>
T g() const; // expected-note-re {{candidate template ignored: could not match 'T (){{( __attribute__\(\(thiscall\)\))?}} const' against 'char (){{( __attribute__\(\(thiscall\)\))?}}'}}
#if __cplusplus >= 201402L
// expected-note@-2 {{candidate template ignored: could not match 'T () const' against 'int ()'}}
#endif
};
// explicit specialization can differ in constepxr
template <> notlit ft(notlit nl) { return nl; }
template <> char ft(char c) { return c; } // expected-note {{previous}}
template <> constexpr char ft(char nl); // expected-error {{constexpr declaration of 'ft<char>' follows non-constexpr declaration}}
template <> constexpr int gt(int nl) { return nl; }
template <> notlit S::f() const { return notlit(); }
#if __cplusplus >= 201402L
// expected-error@-2 {{no function template matches}}
#endif
template <> constexpr int S::g() { return 0; }
#if __cplusplus < 201402L
// expected-warning@-2 {{C++14}}
// expected-note@-3 {{previous}}
#else
// expected-error@-5 {{no function template matches function template specialization 'g'}}
#endif
template <> int S::g() const;
#if __cplusplus < 201402L
// expected-error@-2 {{non-constexpr declaration of 'g<int>' follows constexpr declaration}}
#endif
// specializations can drop the 'constexpr' but not the implied 'const'.
template <> char S::g() { return 0; } // expected-error {{no function template matches}}
template <> double S::g() const { return 0; } // ok
constexpr int i3 = ft(1);
void test() {
// ignore constexpr when instantiating with non-literal
notlit2 nl2;
(void)ft(nl2);
}
// Examples from the standard:
constexpr int square(int x); // expected-note {{declared here}}
constexpr int bufsz = 1024;
constexpr struct pixel { // expected-error {{struct cannot be marked constexpr}}
int x;
int y;
constexpr pixel(int);
};
constexpr pixel::pixel(int a)
: x(square(a)), y(square(a)) // expected-note {{undefined function 'square' cannot be used in a constant expression}}
{ }
constexpr pixel small(2); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to 'pixel(2)'}}
constexpr int square(int x) {
return x * x;
}
constexpr pixel large(4);
int next(constexpr int x) { // expected-error {{function parameter cannot be constexpr}}
return x + 1;
}
extern constexpr int memsz; // expected-error {{constexpr variable declaration must be a definition}}
namespace {
struct A {
static constexpr int n = 0;
};
// FIXME: We should diagnose this prior to C++17.
const int &r = A::n;
}
#if __cplusplus < 201402L
namespace ImplicitConstexprDef {
struct A {
void f(); // expected-note {{member declaration does not match because it is not const qualified}}
};
constexpr void A::f() { } // expected-warning {{'constexpr' non-static member function will not be implicitly 'const' in C++14; add 'const' to avoid a change in behavior}}
// expected-error@-1 {{out-of-line definition of 'f' does not match any declaration in 'ImplicitConstexprDef::A'}}
}
#endif
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