strict aliasing via C++20's char8_t (merged with master)

base/common/StringRef.h

@@ -26,8 +26,9 @@ struct StringRef
     const char * data = nullptr;
     size_t size = 0;
 
-    StringRef(const char * data_, size_t size_) : data(data_), size(size_) {}
-    StringRef(const unsigned char * data_, size_t size_) : data(reinterpret_cast<const char *>(data_)), size(size_) {}
+    template <typename CharT, typename = std::enable_if_t<sizeof(CharT) == 1>>
+    StringRef(const CharT * data_, size_t size_) : data(reinterpret_cast<const char *>(data_)), size(size_) {}
+
     StringRef(const std::string & s) : data(s.data()), size(s.size()) {}
     StringRef(const std::string_view & s) : data(s.data()), size(s.size()) {}
     explicit StringRef(const char * data_) : data(data_), size(strlen(data_)) {}

base/common/Types.h

@@ -11,7 +11,7 @@ using Int16 = int16_t;
 using Int32 = int32_t;
 using Int64 = int64_t;
 
-using UInt8 = uint8_t;
+using UInt8 = char8_t;
 using UInt16 = uint16_t;
 using UInt32 = uint32_t;
 using UInt64 = uint64_t;

base/common/itoa.h

@@ -397,6 +397,12 @@ char * itoa(I i, char * p)
     return impl::convert::itoa(i, p);
 }
 
+template <>
+inline char * itoa(char8_t i, char * p)
+{
+    return impl::convert::itoa(uint8_t(i), p);
+}
+
 template <>
 inline char * itoa<uint128_t>(uint128_t i, char * p)
 {

base/mysqlxx/include/mysqlxx/Value.h

@@ -239,6 +239,7 @@ template <> inline bool                 Value::get<bool                 >() cons
 template <> inline char                 Value::get<char                 >() const { return getInt(); }
 template <> inline signed char          Value::get<signed char          >() const { return getInt(); }
 template <> inline unsigned char        Value::get<unsigned char        >() const { return getUInt(); }
+template <> inline char8_t              Value::get<char8_t              >() const { return getUInt(); }
 template <> inline short                Value::get<short                >() const { return getInt(); }
 template <> inline unsigned short       Value::get<unsigned short       >() const { return getUInt(); }
 template <> inline int                  Value::get<int                  >() const { return getInt(); }

dbms/src/Access/Authentication.cpp

@@ -87,4 +87,3 @@ void Authentication::checkPassword(const String & password_, const String & user
 }
 
 }
-

dbms/src/Access/Authentication.h

@@ -37,7 +37,7 @@ class Authentication
         DOUBLE_SHA1_PASSWORD,
     };
 
-    using Digest = std::vector<UInt8>;
+    using Digest = std::vector<uint8_t>;
 
     Authentication(Authentication::Type type_ = NO_PASSWORD) : type(type_) {}
     Authentication(const Authentication & src) = default;

dbms/src/AggregateFunctions/AggregateFunctionGroupBitmapData.h

@@ -655,7 +655,7 @@ class RoaringBitmapWithSmallSet : private boost::noncopyable
         }
     }
 
-    UInt32 db_container_to_uint32_array(DB::WriteBuffer & dbBuf, const void * container, UInt8 typecode, UInt32 base) const
+    UInt32 db_container_to_uint32_array(DB::WriteBuffer & dbBuf, const void * container, uint8_t typecode, UInt32 base) const
     {
         container = container_unwrap_shared(container, &typecode);
         switch (typecode)

dbms/src/AggregateFunctions/QuantileTiming.h

@@ -487,7 +487,7 @@ class QuantileTiming : private boost::noncopyable
         detail::QuantileTimingLarge * large;
     };
 
-    enum class Kind : UInt8
+    enum class Kind : uint8_t
     {
         Tiny = 1,
         Medium = 2,

dbms/src/Columns/ColumnNullable.cpp

@@ -115,7 +115,7 @@ StringRef ColumnNullable::serializeValueIntoArena(size_t n, Arena & arena, char
 
 const char * ColumnNullable::deserializeAndInsertFromArena(const char * pos)
 {
-    UInt8 val = *reinterpret_cast<const UInt8 *>(pos);
+    UInt8 val = unalignedLoad<UInt8>(pos);
     pos += sizeof(val);
 
     getNullMapData().push_back(val);

dbms/src/Columns/ColumnUnique.h

@@ -325,7 +325,7 @@ size_t ColumnUnique<ColumnType>::uniqueDeserializeAndInsertFromArena(const char
 {
     if (is_nullable)
     {
-        UInt8 val = *reinterpret_cast<const UInt8 *>(pos);
+        UInt8 val = unalignedLoad<UInt8>(pos);
         pos += sizeof(val);
 
         if (val)

dbms/src/Common/CombinedCardinalityEstimator.h

@@ -12,11 +12,11 @@ namespace DB
 namespace details
 {
 
-enum class ContainerType : UInt8 { SMALL = 1, MEDIUM = 2, LARGE = 3 };
+enum class ContainerType : uint8_t { SMALL = 1, MEDIUM = 2, LARGE = 3 };
 
 static inline ContainerType max(const ContainerType & lhs, const ContainerType & rhs)
 {
-    UInt8 res = std::max(static_cast<UInt8>(lhs), static_cast<UInt8>(rhs));
+    uint8_t res = std::max(static_cast<uint8_t>(lhs), static_cast<uint8_t>(rhs));
     return static_cast<ContainerType>(res);
 }