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145
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1 /* { dg-do run } */
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2 /* { dg-additional-options "-fstrict-aliasing" } */
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3
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4 #include <cstdlib>
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5 #include <array>
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6 #include <type_traits>
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7
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8 template <typename T1, typename T2>
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9 struct variant
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10 {
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11 constexpr variant(T1 arg)
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12 : f1(arg),
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13 index(0)
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14 {}
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15
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16 constexpr variant(T2 arg)
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17 : f2(arg),
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18 index(1)
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19 {}
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20
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21 union
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22 {
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23 T1 f1;
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24 T2 f2;
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25 };
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26 std::size_t index = 0;
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27 };
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28
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29 template <typename T1, typename T2>
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30 constexpr const T1* get_if(const variant<T1, T2>* v)
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31 {
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32 if (v->index != 0)
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33 {
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34 return nullptr;
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35 }
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36 return &v->f1;
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37 }
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38
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39 template <typename T2, typename T1>
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40 constexpr const T2* get_if(const variant<T1, T2>* v)
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41 {
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42 if (v->index != 1)
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43 {
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44 return nullptr;
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45 }
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46 return &v->f2;
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47 }
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48
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49 template <typename T, size_t N>
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50 struct my_array
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51 {
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52 constexpr const T* begin() const
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53 {
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54 return data;
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55 }
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56
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57 constexpr const T* end() const
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58 {
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59 return data + N;
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60 }
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61
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62 T data[N];
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63 };
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64
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65 template <typename ...Ts>
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66 constexpr auto get_array_of_variants(Ts ...ptrs)
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67 {
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68 return std::array<variant<std::decay_t<Ts>...>, sizeof...(Ts)>{ ptrs... };
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69 }
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70
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71 template <typename T>
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72 constexpr auto get_member_functions();
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73
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74 template <typename Member, typename Class>
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75 constexpr int getFuncId(Member (Class::*memFuncPtr))
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76 {
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77 int idx = 0u;
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78 for (auto &anyFunc : get_member_functions<Class>())
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79 {
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80 if (auto *specificFunc = get_if<Member (Class::*)>(&anyFunc))
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81 {
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82 if (*specificFunc == memFuncPtr)
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83 {
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84 return idx;
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85 }
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86 }
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87 ++idx;
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88 }
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89 std::abort();
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90 }
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91
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92 struct MyStruct
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93 {
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94 void fun1(int /*a*/) {}
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95
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96 int fun2(char /*b*/, short /*c*/, bool /*d*/) { return 0; }
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97
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98 };
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99
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100 template <>
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101 constexpr auto get_member_functions<MyStruct>()
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102 {
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103 return get_array_of_variants(&MyStruct::fun1, &MyStruct::fun2);
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104 }
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105
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106 int main()
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107 {
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108 return getFuncId(&MyStruct::fun1);
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109 }
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