Removed useless code [#CLICKHOUSE-2].

libs/libcommon/include/ext/bit_cast.h

 #pragma once
 
+#include <string>
 #include <type_traits>
 
 
 namespace ext
 {
-    template <typename To, typename From>
-    union bit_cast_helper_t
-    {
-        using dst = std::decay_t<To>;
-        using src = std::decay_t<From>;
-
-        static_assert(std::is_copy_constructible<dst>::value, "destination type must be CopyConstructible");
-        static_assert(std::is_copy_constructible<src>::value, "source type must be CopyConstructible");
-
-        /** value-initialize member `to` first in case destination type is larger than source */
-        dst to{};
-        src from;
-
-        bit_cast_helper_t(const From & from) : from{from} {}
-
-        operator dst() const { return to; }
-    };
-
     /** \brief Returns value `from` converted to type `To` while retaining bit representation.
-     *    `To` and `From` must satisfy `CopyConstructible`. */
+      *    `To` and `From` must satisfy `CopyConstructible`.
+      */
     template <typename To, typename From>
     std::decay_t<To> bit_cast(const From & from)
     {
-        return bit_cast_helper_t<To, From>{from};
+        To res {};
+        memcpy(&res, &from, std::min(sizeof(res), sizeof(from)));
+        return res;
     };
 
     /** \brief Returns value `from` converted to type `To` while retaining bit representation.
-     *    `To` and `From` must satisfy `CopyConstructible`. */
+      *    `To` and `From` must satisfy `CopyConstructible`.
+      */
     template <typename To, typename From>
     std::decay_t<To> safe_bit_cast(const From & from)
     {
         static_assert(sizeof(To) == sizeof(From), "bit cast on types of different width");
-        return bit_cast_helper_t<To, From>{from};
+        return bit_cast<To, From>(from);
     };
 }