clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p9.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
   2 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++2a %s
   3
   4 // A constexpr specifier used in an object declaration declares the object as
   5 // const.
   6 constexpr int a = 0;
   7 extern const int a;
   8
   9 int i; // expected-note 2{{here}}
  10 constexpr int *b = &i;
  11 extern int *const b;
  12
  13 constexpr int &c = i;
  14 extern int &c;
  15
  16 constexpr int (*d)(int) = 0;
  17 extern int (*const d)(int);
  18
  19 // A variable declaration which uses the constexpr specifier shall have an
  20 // initializer and shall be initialized by a constant expression.
  21 constexpr int ni1; // expected-error {{constexpr variable 'ni1' must be initialized by a constant expression}}
  22 constexpr struct C { C(); } ni2; // expected-error {{cannot have non-literal type 'const struct C'}} expected-note 3{{has no constexpr constructors}}
  23 constexpr double &ni3; // expected-error {{declaration of reference variable 'ni3' requires an initializer}}
  24
  25 constexpr int nc1 = i; // expected-error {{constexpr variable 'nc1' must be initialized by a constant expression}} expected-note {{read of non-const variable 'i' is not allowed in a constant expression}}
  26 constexpr C nc2 = C(); // expected-error {{cannot have non-literal type 'const C'}}
  27 int &f(); // expected-note 2{{declared here}}
  28 constexpr int &nc3 = f(); // expected-error {{constexpr variable 'nc3' must be initialized by a constant expression}} expected-note {{non-constexpr function 'f' cannot be used in a constant expression}}
  29 constexpr int nc4(i); // expected-error {{constexpr variable 'nc4' must be initialized by a constant expression}} expected-note {{read of non-const variable 'i' is not allowed in a constant expression}}
  30 constexpr C nc5((C())); // expected-error {{cannot have non-literal type 'const C'}}
  31 constexpr int &nc6(f()); // expected-error {{constexpr variable 'nc6' must be initialized by a constant expression}} expected-note {{non-constexpr function 'f'}}
  32
  33 struct pixel {
  34   int x, y;
  35 };
  36 constexpr pixel ur = { 1294, 1024 }; // ok
  37 constexpr pixel origin;              // expected-error {{default initialization of an object of const type 'const pixel' without a user-provided default constructor}}
  38
  39 #if __cplusplus > 201702L
  40 // A constexpr variable shall have constant destruction.
  41 struct A {
  42   bool ok;
  43   constexpr A(bool ok) : ok(ok) {}
  44   constexpr ~A() noexcept(false) {
  45     void oops(); // expected-note 6{{declared here}}
  46     if (!ok) oops(); // expected-note 6{{non-constexpr function}}
  47   }
  48 };
  49
  50 struct B {
  51   A a[2];
  52   constexpr B(bool ok) : a{A(!ok), A(ok)}{}
  53 };
  54
  55 struct Cons {
  56   bool val[2];
  57   constexpr Cons() : val{true, false} {}
  58 };
  59
  60 constexpr A const_dtor(true);
  61 static_assert(B(false).a[1].ok); // expected-error {{static assertion expression is not an integral constant expression}} \
  62                                     expected-note {{in call to 'B(false).a[1].~A()'}} expected-note {{in call to 'B(false).~B()'}}
  63 static_assert(B(true).a[1].ok); // expected-error {{static assertion expression is not an integral constant expression}} \
  64                                    expected-note {{in call to 'B(true).a[0].~A()'}} expected-note {{in call to 'B(true).~B()'}}
  65 static_assert(B(Cons().val[1]).a[1].ok); // expected-error {{static assertion expression is not an integral constant expression}} \
  66                                             expected-note {{in call to 'B(Cons().val[1]).a[1].~A()'}} expected-note {{in call to 'B(Cons().val[1]).~B()'}}
  67 static_assert(B((new Cons)->val[0]).a[1].ok); // expected-error {{static assertion expression is not an integral constant expression}} \
  68                                                  expected-note {{in call to 'B((new Cons)->val[0]).a[0].~A()'}} expected-note {{in call to 'B((new Cons)->val[0]).~B()'}}
  69 constexpr A non_const_dtor(false); // expected-error {{must have constant destruction}} expected-note {{in call}}
  70 constexpr A arr_dtor[5] = {true, true, true, false, true}; // expected-error {{must have constant destruction}} expected-note {{in call to 'arr_dtor[3].~A()'}}
  71 #endif