p5.cpp revision 840462670ba7a6bc26265a2306b35f2f0f01f51c 
1// RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -verify -std=c++11 -fcxx-exceptions %s
2// RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -std=c++11 -fcxx-exceptions -Wno-invalid-constexpr %s -DNO_INVALID_CONSTEXPR
3
4namespace StdExample {
5
6constexpr int f(void *) { return 0; }
7constexpr int f(...) { return 1; }
8constexpr int g1() { return f(0); }
9constexpr int g2(int n) { return f(n); }
10constexpr int g3(int n) { return f(n*0); }
11
12namespace N {
13  constexpr int c = 5;
14  constexpr int h() { return c; }
15}
16constexpr int c = 0;
17constexpr int g4() { return N::h(); }
18
19static_assert(f(0) == 0, "");
20static_assert(f('0') == 1, "");
21static_assert(g1() == 0, "");
22static_assert(g2(0) == 1, "");
23static_assert(g2(1) == 1, "");
24static_assert(g3(0) == 1, "");
25static_assert(g3(1) == 1, "");
26static_assert(N::h() == 5, "");
27static_assert(g4() == 5, "");
28
29
30constexpr int f(bool b)
31  { return b ? throw 0 : 0; } // ok
32constexpr int f() { return throw 0, 0; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{subexpression}}
33
34struct B {
35  constexpr B(int x) : i(0) { }
36  int i;
37};
38
39int global; // expected-note {{declared here}}
40
41struct D : B {
42  constexpr D() : B(global) { } // expected-error {{constexpr constructor never produces a constant expression}} expected-note {{read of non-const}}
43};
44
45}
46
47namespace PotentialConstant {
48
49constexpr int Comma(int n) { return // expected-error {{constexpr function never produces a constant expression}}
50  (void)(n * 2),
51  throw 0, // expected-note {{subexpression}}
52  0;
53}
54
55int ng; // expected-note 6{{here}}
56constexpr int BinaryOp1(int n) { return n + ng; } // expected-error {{never produces}} expected-note {{read}}
57constexpr int BinaryOp2(int n) { return ng + n; } // expected-error {{never produces}} expected-note {{read}}
58
59double dg; // expected-note 2{{here}}
60constexpr double BinaryOp1(double d) { return d + dg; } // expected-error {{never produces}} expected-note {{read}}
61constexpr double BinaryOp2(double d) { return dg + d; } // expected-error {{never produces}} expected-note {{read}}
62
63constexpr int Add(int a, int b, int c) { return a + b + c; }
64constexpr int FunctionArgs(int a) { return Add(a, ng, a); } // expected-error {{never produces}} expected-note {{read}}
65
66struct S { int a; int b; int c[2]; };
67constexpr S InitList(int a) { return { a, ng }; }; // expected-error {{never produces}} expected-note {{read}}
68constexpr S InitList1a(int a) { return S{ a, ng }; }; // expected-error {{never produces}} expected-note {{read}}
69constexpr S InitList2(int a) { return { a, a, { ng } }; }; // expected-error {{never produces}} expected-note {{read}}
70constexpr S InitList3(int a) { return a ? S{ a, a } : S{ a, ng }; }; // ok
71
72constexpr int LogicalAnd1(int n) { return n && (throw, 0); } // ok
73constexpr int LogicalAnd2(int n) { return 1 && (throw, 0); } // expected-error {{never produces}} expected-note {{subexpression}}
74
75constexpr int LogicalOr1(int n) { return n || (throw, 0); } // ok
76constexpr int LogicalOr2(int n) { return 0 || (throw, 0); } // expected-error {{never produces}} expected-note {{subexpression}}
77
78constexpr int Conditional1(bool b, int n) { return b ? n : ng; } // ok
79constexpr int Conditional2(bool b, int n) { return b ? n * ng : n + ng; } // expected-error {{never produces}} expected-note {{both arms of conditional operator are unable to produce a constant expression}}
80
81// __builtin_constant_p ? : is magical, and is always a potential constant.
82constexpr bool BcpCall(int n) {
83  return __builtin_constant_p((int*)n != &n) ? (int*)n != &n : (int*)n != &n; // expected-warning 3 {{cast to 'int *' from smaller integer type 'int'}}
84}
85static_assert(BcpCall(0), "");
86
87// DR1311: A function template which can produce a constant expression, but
88// for which a particular specialization cannot, is ok.
89template<typename T> constexpr T cmin(T a, T b) {
90  return a < b ? a : b;
91}
92int n = cmin(3, 5); // ok
93
94struct X {
95  constexpr X() {}
96  bool operator<(X); // not constexpr
97};
98
99X x = cmin(X(), X()); // ok, not constexpr
100
101// Same with other temploids.
102template<typename T>
103struct Y {
104  constexpr Y() {}
105  constexpr int get() { return T(); } // expected-warning {{C++1y}}
106};
107struct Z { operator int(); };
108
109int y1 = Y<int>().get(); // ok
110int y2 = Y<Z>().get(); // ok
111
112}
113
114#ifndef NO_INVALID_CONSTEXPR
115namespace PR14550 {
116  // As an "extension", we allow functions which can't produce constant
117  // expressions to be declared constexpr in system headers (libstdc++
118  // marks some functions as constexpr which use builtins which we don't
119  // support constant folding). Ensure that we don't mark those functions
120  // as invalid after suppressing the diagnostic.
121# 122 "p5.cpp" 1 3
122  int n;
123  struct A {
124    static constexpr int f() { return n; }
125  };
126  template<typename T> struct B {
127    B() { g(T::f()); } // expected-error {{undeclared identifier 'g'}}
128  };
129# 130 "p5.cpp" 2
130  template class B<A>; // expected-note {{here}}
131}
132#endif
133