Viewing file:  pr91606.C (1.76 KB) -rw-r--r--
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/* { dg-do run } */
/* { dg-additional-options "-fstrict-aliasing" } */
#include <cstdlib>
#include <array>
#include <type_traits>
template <typename T1, typename T2>
struct variant
{
constexpr variant(T1 arg)
: f1(arg),
index(0)
{}
constexpr variant(T2 arg)
: f2(arg),
index(1)
{}
union
{
T1 f1;
T2 f2;
};
std::size_t index = 0;
};
template <typename T1, typename T2>
constexpr const T1* get_if(const variant<T1, T2>* v)
{
if (v->index != 0)
{
return nullptr;
}
return &v->f1;
}
template <typename T2, typename T1>
constexpr const T2* get_if(const variant<T1, T2>* v)
{
if (v->index != 1)
{
return nullptr;
}
return &v->f2;
}
template <typename T, size_t N>
struct my_array
{
constexpr const T* begin() const
{
return data;
}
constexpr const T* end() const
{
return data + N;
}
T data[N];
};
template <typename ...Ts>
constexpr auto get_array_of_variants(Ts ...ptrs)
{
return std::array<variant<std::decay_t<Ts>...>, sizeof...(Ts)>{ ptrs... };
}
template <typename T>
constexpr auto get_member_functions();
template <typename Member, typename Class>
constexpr int getFuncId(Member (Class::*memFuncPtr))
{
int idx = 0u;
for (auto &anyFunc : get_member_functions<Class>())
{
if (auto *specificFunc = get_if<Member (Class::*)>(&anyFunc))
{
if (*specificFunc == memFuncPtr)
{
return idx;
}
}
++idx;
}
std::abort();
}
struct MyStruct
{
void fun1(int /*a*/) {}
int fun2(char /*b*/, short /*c*/, bool /*d*/) { return 0; }
};
template <>
constexpr auto get_member_functions<MyStruct>()
{
return get_array_of_variants(&MyStruct::fun1, &MyStruct::fun2);
}
int main()
{
return getFuncId(&MyStruct::fun1);
}
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