To avoid warning from Clang version 11 and later, change to
FRAME_TEXT = static_cast< int >(FRAME_FLAG_FIN) | static_cast< int >(FRAME_OP_TEXT),

Also do the same change for FRAME_BINARY
FRAME_BINARY = static_cast< int >(FRAME_FLAG_FIN) | static_cast< int >(FRAME_OP_BINARY)