aboutsummaryrefslogtreecommitdiff
path: root/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp
blob: 3986dc9565c394dc038498de978519f9fd840bbf (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
// RUN: %clang_cc1 -verify -fcxx-exceptions -triple=x86_64-linux-gnu -std=c++11 -Werror=c++1y-extensions %s
// RUN: %clang_cc1 -verify -fcxx-exceptions -triple=x86_64-linux-gnu -std=c++1y -DCXX1Y %s

namespace N {
  typedef char C;
}

namespace M {
  typedef double D;
}

struct NonLiteral { // expected-note 3{{no constexpr constructors}}
  NonLiteral() {}
  NonLiteral(int) {}
};
struct Literal {
  constexpr Literal() {}
  operator int() const { return 0; }
};

struct S {
  virtual int ImplicitlyVirtual() const = 0; // expected-note {{overridden virtual function}}
};
struct SS : S {
  int ImplicitlyVirtual() const;
};

// The definition of a constexpr function shall satisfy the following
// constraints:
struct T : SS, NonLiteral {
  constexpr T();
  constexpr int f() const;

  //  - it shall not be virtual;
  virtual constexpr int ExplicitlyVirtual() const { return 0; } // expected-error {{virtual function cannot be constexpr}}

  constexpr int ImplicitlyVirtual() const { return 0; } // expected-error {{virtual function cannot be constexpr}}

  virtual constexpr int OutOfLineVirtual() const; // expected-error {{virtual function cannot be constexpr}}

  //  - its return type shall be a literal type;
  constexpr NonLiteral NonLiteralReturn() const { return {}; } // expected-error {{constexpr function's return type 'NonLiteral' is not a literal type}}
  constexpr void VoidReturn() const { return; }
#ifndef CXX1Y
  // expected-error@-2 {{constexpr function's return type 'void' is not a literal type}}
#endif
  constexpr ~T(); // expected-error {{destructor cannot be marked constexpr}}
  typedef NonLiteral F() const;
  constexpr F NonLiteralReturn2; // ok until definition

  //  - each of its parameter types shall be a literal type;
  constexpr int NonLiteralParam(NonLiteral) const { return 0; } // expected-error {{constexpr function's 1st parameter type 'NonLiteral' is not a literal type}}
  typedef int G(NonLiteral) const;
  constexpr G NonLiteralParam2; // ok until definition

  //  - its function-body shall be = delete, = default,
  constexpr int Deleted() const = delete;
  // It's not possible for the function-body to legally be "= default" here
  // (that is, for a non-constructor function) in C++11.
  // Other than constructors, only the copy- and move-assignment operators and
  // destructor can be defaulted. Destructors can't be constexpr since they
  // don't have a literal return type. Defaulted assignment operators can't be
  // constexpr since they can't be const.
  constexpr T &operator=(const T&) = default;
#ifndef CXX1Y
  // expected-error@-2 {{an explicitly-defaulted copy assignment operator may not have 'const', 'constexpr' or 'volatile' qualifiers}}
  // expected-warning@-3 {{C++14}}
#else
  // expected-error@-5 {{defaulted definition of copy assignment operator is not constexpr}}
#endif
};

constexpr int T::OutOfLineVirtual() const { return 0; }
#ifdef CXX1Y
struct T2 {
  int n = 0;
  constexpr T2 &operator=(const T2&) = default; // ok
};
struct T3 {
  constexpr T3 &operator=(const T3&) const = default;
  // expected-error@-1 {{an explicitly-defaulted copy assignment operator may not have 'const' or 'volatile' qualifiers}}
};
#endif
struct U {
  constexpr U SelfReturn() const;
  constexpr int SelfParam(U) const;
};

struct V : virtual U { // expected-note {{here}}
  constexpr int F() const { return 0; } // expected-error {{constexpr member function not allowed in struct with virtual base class}}
};

//  or a compound-statememt that contains only [CXX11]
constexpr int AllowedStmtsCXX11() {
  //  - null statements
  ;

  //  - static_assert-declarations
  static_assert(true, "the impossible happened!");

  //  - typedef declarations and alias-declarations that do not define classes
  //    or enumerations
  typedef int I;
  typedef struct S T;
  using J = int;
  using K = int[sizeof(I) + sizeof(J)];
  // Note, the standard requires we reject this.
  struct U;

  //  - using-declarations
  using N::C;

  //  - using-directives
  using namespace N;

  //  - and exactly one return statement
  return sizeof(K) + sizeof(C) + sizeof(K);
}

//  or a compound-statement that does not contain [CXX1Y]
constexpr int DisallowedStmtsCXX1Y_1() {
  //  - an asm-definition
  asm("int3"); // expected-error {{statement not allowed in constexpr function}}
  return 0;
}
constexpr int DisallowedStmtsCXX1Y_2() {
  //  - a goto statement
  goto x; // expected-error {{statement not allowed in constexpr function}}
x:
  return 0;
}
constexpr int DisallowedStmtsCXX1Y_3() {
  //  - a try-block,
  try {} catch (...) {} // expected-error {{statement not allowed in constexpr function}}
  return 0;
}
constexpr int DisallowedStmtsCXX1Y_4() {
  //  - a definition of a variable of non-literal type
  NonLiteral nl; // expected-error {{variable of non-literal type 'NonLiteral' cannot be defined in a constexpr function}}
  return 0;
}
constexpr int DisallowedStmtsCXX1Y_5() {
  //  - a definition of a variable of static storage duration
  static constexpr int n = 123; // expected-error {{static variable not permitted in a constexpr function}}
  return n;
}
constexpr int DisallowedStmtsCXX1Y_6() {
  //  - a definition of a variable of thread storage duration
  thread_local constexpr int n = 123; // expected-error {{thread_local variable not permitted in a constexpr function}}
  return n;
}
constexpr int DisallowedStmtsCXX1Y_7() {
  //  - a definition of a variable for which no initialization is performed
  int n; // expected-error {{variables defined in a constexpr function must be initialized}}
  return 0;
}

constexpr int ForStmt() {
  for (int n = 0; n < 10; ++n)
#ifndef CXX1Y
  // expected-error@-2 {{statement not allowed in constexpr function}}
#endif
    return 0;
}
constexpr int VarDecl() {
  int a = 0;
#ifndef CXX1Y
  // expected-error@-2 {{variable declaration in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
constexpr int ConstexprVarDecl() {
  constexpr int a = 0;
#ifndef CXX1Y
  // expected-error@-2 {{variable declaration in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
constexpr int VarWithCtorDecl() {
  Literal a;
#ifndef CXX1Y
  // expected-error@-2 {{variable declaration in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
NonLiteral nl;
constexpr NonLiteral &ExternNonLiteralVarDecl() {
  extern NonLiteral nl;
#ifndef CXX1Y
  // expected-error@-2 {{variable declaration in a constexpr function is a C++14 extension}}
#endif
  return nl;
}
static_assert(&ExternNonLiteralVarDecl() == &nl, "");
constexpr int FuncDecl() {
  constexpr int ForwardDecl(int);
#ifndef CXX1Y
  // expected-error@-2 {{use of this statement in a constexpr function is a C++14 extension}}
#endif
  return ForwardDecl(42);
}
constexpr int ClassDecl1() {
  typedef struct { } S1;
#ifndef CXX1Y
  // expected-error@-2 {{type definition in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
constexpr int ClassDecl2() {
  using S2 = struct { };
#ifndef CXX1Y
  // expected-error@-2 {{type definition in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
constexpr int ClassDecl3() {
  struct S3 { };
#ifndef CXX1Y
  // expected-error@-2 {{type definition in a constexpr function is a C++14 extension}}
#endif
  return 0;
}
constexpr int NoReturn() {} // expected-error {{no return statement in constexpr function}}
constexpr int MultiReturn() {
  return 0;
  return 0;
#ifndef CXX1Y
  // expected-error@-2 {{multiple return statements in constexpr function}}
  // expected-note@-4 {{return statement}}
#endif
}

//  - every constructor call and implicit conversion used in initializing the
//    return value shall be one of those allowed in a constant expression.
//
// We implement the proposed resolution of DR1364 and ignore this bullet.
// However, we implement the spirit of the check as part of the p5 checking that
// a constexpr function must be able to produce a constant expression.
namespace DR1364 {
  constexpr int f(int k) {
    return k; // ok, even though lvalue-to-rvalue conversion of a function
              // parameter is not allowed in a constant expression.
  }
  int kGlobal; // expected-note {{here}}
  constexpr int f() { // expected-error {{constexpr function never produces a constant expression}}
    return kGlobal; // expected-note {{read of non-const}}
  }
}

namespace rdar13584715 {
  typedef __PTRDIFF_TYPE__ ptrdiff_t;

  template<typename T> struct X {
    static T value() {};
  };

  void foo(ptrdiff_t id) {
    switch (id) {
    case reinterpret_cast<ptrdiff_t>(&X<long>::value):  // expected-error{{case value is not a constant expression}} \
      // expected-note{{reinterpret_cast is not allowed in a constant expression}}
      break;
    }
  }
}

namespace std_example {
  constexpr int square(int x) {
    return x * x;
  }
  constexpr long long_max() {
    return 2147483647;
  }
  constexpr int abs(int x) {
    if (x < 0)
#ifndef CXX1Y
      // expected-error@-2 {{C++14}}
#endif
      x = -x;
    return x;
  }
  constexpr int first(int n) {
    static int value = n; // expected-error {{static variable not permitted}}
    return value;
  }
  constexpr int uninit() {
    int a; // expected-error {{must be initialized}}
    return a;
  }
  constexpr int prev(int x) {
    return --x;
  }
#ifndef CXX1Y
  // expected-error@-4 {{never produces a constant expression}}
  // expected-note@-4 {{subexpression}}
#endif
  constexpr int g(int x, int n) {
    int r = 1;
    while (--n > 0) r *= x;
    return r;
  }
#ifndef CXX1Y
    // expected-error@-5 {{C++14}}
    // expected-error@-5 {{statement not allowed}}
#endif
}