p5.cpp revision d79093af384ac0ea78f4237a001eae7467e06a61 
1// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -fcxx-exceptions %s
2
3namespace StdExample {
4
5constexpr int f(void *) { return 0; }
6constexpr int f(...) { return 1; }
7constexpr int g1() { return f(0); }
8constexpr int g2(int n) { return f(n); }
9constexpr int g3(int n) { return f(n*0); }
10
11namespace N {
12  constexpr int c = 5;
13  constexpr int h() { return c; }
14}
15constexpr int c = 0;
16constexpr int g4() { return N::h(); }
17
18static_assert(f(0) == 0, "");
19static_assert(f('0') == 1, "");
20static_assert(g1() == 0, "");
21static_assert(g2(0) == 1, "");
22static_assert(g2(1) == 1, "");
23static_assert(g3(0) == 1, "");
24static_assert(g3(1) == 1, "");
25static_assert(N::h() == 5, "");
26static_assert(g4() == 5, "");
27
28
29constexpr int f(bool b)
30  { return b ? throw 0 : 0; } // ok
31constexpr int f() { return throw 0, 0; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{subexpression}}
32
33struct B {
34  constexpr B(int x) : i(0) { }
35  int i;
36};
37
38int global; // expected-note {{declared here}}
39
40struct D : B {
41  constexpr D() : B(global) { } // expected-error {{constexpr constructor never produces a constant expression}} expected-note {{read of non-const}}
42};
43
44}
45
46namespace PotentialConstant {
47
48constexpr int Comma(int n) { return // expected-error {{constexpr function never produces a constant expression}}
49  (void)(n * 2),
50  throw 0, // expected-note {{subexpression}}
51  0;
52}
53
54int ng; // expected-note 5{{here}}
55constexpr int BinaryOp1(int n) { return n + ng; } // expected-error {{never produces}} expected-note {{read}}
56constexpr int BinaryOp2(int n) { return ng + n; } // expected-error {{never produces}} expected-note {{read}}
57
58double dg; // expected-note 2{{here}}
59constexpr double BinaryOp1(double d) { return d + dg; } // expected-error {{never produces}} expected-note {{read}}
60constexpr double BinaryOp2(double d) { return dg + d; } // expected-error {{never produces}} expected-note {{read}}
61
62constexpr int Add(int a, int b, int c) { return a + b + c; }
63constexpr int FunctionArgs(int a) { return Add(a, ng, a); } // expected-error {{never produces}} expected-note {{read}}
64
65struct S { int a; int b; int c[2]; };
66constexpr S InitList(int a) { return { a, ng }; }; // expected-error {{never produces}} expected-note {{read}}
67constexpr S InitList2(int a) { return { a, a, { ng } }; }; // expected-error {{never produces}} expected-note {{read}}
68
69constexpr S InitList3(int a) { return a ? (S){ a, a } : (S){ a, ng }; }; // ok
70
71// FIXME: Check both arms of a ?: if the conditional is a potential constant
72// expression with an unknown value, and diagnose if neither is constant.
73constexpr S InitList4(int a) { return a ? (S){ a, ng } : (S){ a, ng }; };
74
75// __builtin_constant_p ? : is magical, and is always a potential constant.
76constexpr bool BcpCall(int n) {
77  return __builtin_constant_p((int*)n != &n) ? (int*)n != &n : (int*)n != &n;
78}
79static_assert(BcpCall(0), "");
80
81// DR1311: A function template which can produce a constant expression, but
82// for which a particular specialization cannot, is ok.
83template<typename T> constexpr T cmin(T a, T b) {
84  return a < b ? a : b;
85}
86int n = cmin(3, 5); // ok
87
88struct X {
89  constexpr X() {}
90  bool operator<(X); // not constexpr
91};
92
93X x = cmin(X(), X()); // ok, not constexpr
94
95// Same with other temploids.
96template<typename T>
97struct Y {
98  constexpr Y() {}
99  constexpr int get() { return T(); }
100};
101struct Z { operator int(); };
102
103int y1 = Y<int>().get(); // ok
104int y2 = Y<Z>().get(); // ok
105
106}
107