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1 // RUN: %clang_cc1 -std=c++2a -verify %s -fcxx-exceptions -Wno-constant-evaluated -triple=x86_64-linux-gnu
2 
3 #define fold(x) (__builtin_constant_p(x) ? (x) : (x))
4 
5 using size_t = decltype(sizeof(int));
6 
7 namespace std {
is_constant_evaluated()8 inline constexpr bool is_constant_evaluated() noexcept {
9   return __builtin_is_constant_evaluated();
10 }
11 } // namespace std
12 
13 extern int dummy; // expected-note 1+ {{declared here}}
14 
15 static_assert(__builtin_is_constant_evaluated());
16 static_assert(noexcept(__builtin_is_constant_evaluated()));
17 
18 constexpr bool b = __builtin_is_constant_evaluated();
19 static_assert(b);
20 
21 const int n = __builtin_is_constant_evaluated() ? 4 : dummy;
22 static_assert(n == 4);
23 constexpr int cn = __builtin_is_constant_evaluated() ? 11 : dummy;
24 static_assert(cn == 11);
25 // expected-error@+1 {{'bn' must be initialized by a constant expression}}
26 constexpr int bn = __builtin_is_constant_evaluated() ? dummy : 42; // expected-note {{non-const variable 'dummy' is not allowed}}
27 
28 const int n2 = __builtin_is_constant_evaluated() ? dummy : 42; // expected-note {{declared here}}
29 static_assert(n2 == 42);                                       // expected-error {{static_assert expression is not an integral constant}}
30 // expected-note@-1 {{initializer of 'n2' is not a constant expression}}
31 
32 template <bool V, bool Default = std::is_constant_evaluated()>
33 struct Templ { static_assert(V); static_assert(Default); };
34 Templ<__builtin_is_constant_evaluated()> x; // type X<true>
35 
36 template <class T>
test_if_constexpr()37 void test_if_constexpr() {
38   if constexpr (__builtin_is_constant_evaluated()) {
39     static_assert(__is_same(T, int));
40   } else {
41     using Test = typename T::DOES_NOT_EXIST;
42   }
43 }
44 template void test_if_constexpr<int>();
45 
test_array_decl()46 void test_array_decl() {
47   char x[__builtin_is_constant_evaluated() + std::is_constant_evaluated()];
48   static_assert(sizeof(x) == 2, "");
49 }
50 
test_case_stmt(int x)51 void test_case_stmt(int x) {
52   switch (x) {
53   case 0:                                                                // OK
54   case __builtin_is_constant_evaluated():                                // expected-note {{previous case}}
55   case std::is_constant_evaluated() + __builtin_is_constant_evaluated(): // expected-note {{previous case}}
56   case 1:                                                                // expected-error {{duplicate case value '1'}}
57   case 2:                                                                // expected-error {{duplicate case value '2'}}
58     break;
59   }
60 }
61 
good_array_size()62 constexpr size_t good_array_size() {
63   return std::is_constant_evaluated() ? 42 : static_cast<size_t>(-1);
64 }
65 
bad_array_size()66 constexpr size_t bad_array_size() {
67   return std::is_constant_evaluated() ? static_cast<size_t>(-1) : 13;
68 }
69 
70 template <class T>
require_constexpr(T v)71 constexpr T require_constexpr(T v) {
72   if (!std::is_constant_evaluated())
73     throw "BOOM";
74   return v;
75 }
76 
test_new_expr()77 void test_new_expr() {
78   constexpr size_t TooLarge = -1;
79   auto *x = new int[std::is_constant_evaluated() ? 1 : TooLarge];      // expected-error {{array is too large}}
80   auto *x2 = new int[std::is_constant_evaluated() ? TooLarge : 1];     // OK
81   auto *y = new int[1][std::is_constant_evaluated() ? TooLarge : 1]{}; // expected-error {{array is too large}}
82   auto *y2 = new int[1][require_constexpr(42)];
83 }
84 
test_alignas_operand()85 void test_alignas_operand() {
86   alignas(std::is_constant_evaluated() ? 8 : 2) char dummy;
87   static_assert(__alignof(dummy) == 8);
88 }
89 
test_static_assert_operand()90 void test_static_assert_operand() {
91   static_assert(std::is_constant_evaluated(), "");
92 }
93 
test_enumerator()94 void test_enumerator() {
95   enum MyEnum {
96     ZERO = 0,
97     ONE = std::is_constant_evaluated()
98   };
99   static_assert(ONE == 1, "");
100 }
101 
102 struct TestBitfieldWidth {
103   unsigned Bits : std::is_constant_evaluated();
104 };
105 
106 void test_operand_of_noexcept_fn() noexcept(std::is_constant_evaluated());
107 static_assert(noexcept(test_operand_of_noexcept_fn()), "");
108 
109 
110 namespace test_ref_initialization {
111 int x;
112 int y;
113 int &r = __builtin_is_constant_evaluated() ? x : y;
114 static_assert(&r == &x);
115 
116 } // namespace test_ref_initialization
117 
118 #if defined(__cpp_conditional_explicit)
119 struct TestConditionalExplicit {
TestConditionalExplicitTestConditionalExplicit120   explicit(!__builtin_is_constant_evaluated()) TestConditionalExplicit(int) {}
121 };
122 TestConditionalExplicit e = 42;
123 #endif
124 
125 namespace fold_initializer {
126   // Global 'f' has a constant initializer.
127   const float f = __builtin_is_constant_evaluated();
128   static_assert(fold(f == 1.0f));
129 
g()130   void g() {
131     // Local static 'sf' has a constant initializer.
132     static const float sf = __builtin_is_constant_evaluated();
133     static_assert(fold(sf == 1.0f));
134 
135     // Local non-static 'f' has a non-constant initializer.
136     const float f = __builtin_is_constant_evaluated();
137     static_assert(fold(f == 0.0f));
138   }
139 
140   struct A {
141     static const float f;
142   };
143   const float A::f = __builtin_is_constant_evaluated();
144   static_assert(fold(A::f == 1.0f));
145 }
146