constexpr-instantiate.cpp revision 16581335fc32abcbc6ab14eda7af38cf759664b7 
1// RUN: %clang_cc1 -std=c++11 -verify %s
2
3namespace UseBeforeDefinition {
4  struct A {
5    template<typename T> static constexpr T get() { return T(); }
6    // ok, not a constant expression.
7    int n = get<int>();
8  };
9
10  // ok, constant expression.
11  constexpr int j = A::get<int>();
12
13  template<typename T> constexpr int consume(T);
14  // ok, not a constant expression.
15  const int k = consume(0); // expected-note {{here}}
16
17  template<typename T> constexpr int consume(T) { return 0; }
18  // ok, constant expression.
19  constexpr int l = consume(0);
20
21  constexpr int m = k; // expected-error {{constant expression}} expected-note {{initializer of 'k'}}
22}
23
24namespace IntegralConst {
25  template<typename T> constexpr T f(T n) { return n; }
26  enum E {
27    v = f(0), w = f(1) // ok
28  };
29  static_assert(w == 1, "");
30
31  char arr[f('x')]; // ok
32  static_assert(sizeof(arr) == 'x', "");
33}
34
35namespace ConvertedConst {
36  template<typename T> constexpr T f(T n) { return n; }
37  int f() {
38    switch (f()) {
39      case f(4): return 0;
40    }
41    return 1;
42  }
43}
44
45namespace OverloadResolution {
46  template<typename T> constexpr T f(T t) { return t; }
47
48  template<int n> struct S { };
49
50  template<typename T> auto g(T t) -> S<f(sizeof(T))> &;
51  char &f(...);
52
53  template<typename T> auto h(T t[f(sizeof(T))]) -> decltype(&*t) {
54    return t;
55  }
56
57  S<4> &k = g(0);
58  int *p, *q = h(p);
59}
60
61namespace DataMember {
62  template<typename T> struct S { static const int k; };
63  const int n = S<int>::k; // expected-note {{here}}
64  template<typename T> const int S<T>::k = 0;
65  constexpr int m = S<int>::k; // ok
66  constexpr int o = n; // expected-error {{constant expression}} expected-note {{initializer of 'n'}}
67}
68
69namespace Reference {
70  const int k = 5;
71  template<typename T> struct S {
72    static volatile int &r;
73  };
74  template<typename T> volatile int &S<T>::r = const_cast<volatile int&>(k);
75  constexpr int n = const_cast<int&>(S<int>::r);
76  static_assert(n == 5, "");
77}
78