In file included from /usr/include/c++/11/bits/stl_algobase.h:64,
from /usr/include/c++/11/bits/char_traits.h:39,
from /usr/include/c++/11/string:40,
from /usr/include/c++/11/stdexcept:39,
from /usr/include/c++/11/system_error:41,
from /usr/include/c++/11/bits/std_mutex.h:39,
from /usr/include/c++/11/bits/atomic_wait.h:49,
from /usr/include/c++/11/bits/atomic_base.h:41,
from /usr/include/c++/11/atomic:41,
from ../../zen/globals.h:10,
from ../../zen/i18n.h:12,
from <command-line>:
/usr/include/c++/11/bits/stl_pair.h: In instantiation of 'struct std::pair<fff::FolderAttributes, fff::FolderContainer>':
/usr/include/c++/11/bits/stl_pair.h:218:11: required from 'struct std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >'
/usr/include/c++/11/ext/aligned_buffer.h:91:28: required from 'struct __gnu_cxx::__aligned_buffer<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> > >'
/usr/include/c++/11/bits/hashtable_policy.h:234:43: required from 'struct std::__detail::_Hash_node_value_base<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> > >'
/usr/include/c++/11/bits/hashtable_policy.h:268:12: required from 'struct std::__detail::_Hash_node_value<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, true>'
/usr/include/c++/11/bits/hashtable_policy.h:277:12: required from 'struct std::__detail::_Hash_node<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, true>'
/usr/include/c++/11/bits/hashtable_policy.h:1812:13: required from 'struct std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, true> > >'
/usr/include/c++/11/bits/hashtable_policy.h:811:13: required from 'struct std::__detail::_Insert_base<zen::Zbase<char>, std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, std::allocator<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> > >, std::__detail::_Select1st, std::equal_to<zen::Zbase<char> >, std::hash<zen::Zbase<char> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, false, true> >'
/usr/include/c++/11/bits/hashtable_policy.h:1004:12: required from 'struct std::__detail::_Insert<zen::Zbase<char>, std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, std::allocator<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> > >, std::__detail::_Select1st, std::equal_to<zen::Zbase<char> >, std::hash<zen::Zbase<char> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, false, true>, false>'
/usr/include/c++/11/bits/hashtable.h:180:11: required from 'class std::_Hashtable<zen::Zbase<char>, std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >, std::allocator<std::pair<const zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> > >, std::__detail::_Select1st, std::equal_to<zen::Zbase<char> >, std::hash<zen::Zbase<char> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, false, true> >'
/usr/include/c++/11/bits/unordered_map.h:105:18: required from 'class std::unordered_map<zen::Zbase<char>, std::pair<fff::FolderAttributes, fff::FolderContainer> >'
base/file_hierarchy.h:108:17: required from here
/usr/include/c++/11/bits/stl_pair.h:218:11: error: 'std::pair<_T1, _T2>::second' has incomplete type
218 | _T2 second; ///< The second member
| ^~~~~~
compilation terminated due to -Wfatal-errors.
make: *** [Makefile:132: /tmp/FreeFileSync_Make/ffs/src/application.cpp.o] Error 1
make: Leaving directory '/usr/src/freefilesync/11.21-1/FreeFileSync/Source'
I see that in the past, line 108 of file_hierarchy.h used std::map and not std::unordered_map. Could I switch back to that, and what would the caveats be?