gcc 9.2.1 reports -Werror=stringop-overflow in os_file_get_parent_dir

In file included from /usr/include/string.h:494,
                 from /data/mysql-server/mysql-8.0/include/my_dbug.h:37,
                 from /data/mysql-server/mysql-8.0/storage/innobase/include/os0file.h:44,
                 from /data/mysql-server/mysql-8.0/storage/innobase/os/os0file.cc:41:
In function ‘void* memcpy(void*, const void*, size_t)’,
    inlined from ‘char* mem_strdupl(const char*, ulint)’ at /data/mysql-server/mysql-8.0/storage/innobase/include/mem0mem.ic:555:11,
    inlined from ‘char* os_file_get_parent_dir(const char*)’ at /data/mysql-server/mysql-8.0/storage/innobase/os/os0file.cc:1794:22,
    inlined from ‘dberr_t os_file_create_subdirs_if_needed(const char*)’ at /data/mysql-server/mysql-8.0/storage/innobase/os/os0file.cc:1863:40:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:34:33: error: ‘void* __builtin_memcpy(void*, const void*, long unsigned int)’ specified bound 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Werror=stringop-overflow=]
   34 |   return __builtin___memcpy_chk (__dest, __src, __len, __bos0 (__dest));
      |          ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors