Following ICEs:

$ g++ -shared -fPIC -flto=8 -O2 -std=gnu++17 libre-1.ii libre-2.ii libre-3.ii
libre-1.ii:139:7: warning: type ‘struct XclRoot’ violates the C++ One Definition Rule [-Wodr]
 class XclRoot {
       ^
libre-2.ii:1:7: note: a different type is defined in another translation unit
 class XclRoot {
       ^
libre-1.ii:142:16: note: the first difference of corresponding definitions is field ‘mrData’
   XclRootData &mrData;
                ^
libre-2.ii:1:7: note: a type with different number of fields is defined in another translation unit
 class XclRoot {
       ^
libre-1.ii:144:7: warning: type ‘struct XclImpRoot’ violates the C++ One Definition Rule [-Wodr]
 class XclImpRoot : XclRoot {};
       ^
libre-2.ii:5:7: note: a type with different bases is defined in another translation unit
 class XclImpRoot : XclRoot {};
       ^
libre-2.ii:6:8: warning: type ‘struct RootData’ violates the C++ One Definition Rule [-Wodr]
 struct RootData {
        ^
libre-3.ii:121:8: note: a different type is defined in another translation unit
 struct RootData {
        ^
libre-2.ii:7:14: note: the first difference of corresponding definitions is field ‘pIR’
   XclImpRoot pIR;
              ^
libre-3.ii:122:11: note: a field with different name is defined in another translation unit
   BiffTyp eDateiTyp;
           ^
libre-3.ii:18:7: warning: type ‘struct __shared_ptr’ violates the C++ One Definition Rule [-Wodr]
 class __shared_ptr : __shared_ptr_access< a, l > {
       ^
libre-1.ii:21:7: note: a different type is defined in another translation unit
 class __shared_ptr : __shared_ptr_access< _Tp, _Lp > {
       ^
libre-3.ii:20:6: note: the first difference of corresponding definitions is field ‘_M_ptr’
   m *_M_ptr;
      ^
libre-1.ii:23:17: note: a field of same name but different type is defined in another translation unit
   element_type *_M_ptr;
                 ^
libre-3.ii:19:14: note: type ‘struct m’ should match type ‘struct element_type’
   using m = a;
              ^
libre-1.ii:22:27: note: the incompatible type is defined here
   using element_type = _Tp;
                           ^
libre-1.ii:103:8: warning: type ‘struct XclRootData’ violates the C++ One Definition Rule [-Wodr]
 struct XclRootData {
        ^
libre-3.ii:82:8: note: a different type is defined in another translation unit
 struct XclRootData {
        ^
libre-1.ii:136:15: note: the first difference of corresponding definitions is field ‘mxRD’
   RootDataRef mxRD;
               ^
libre-3.ii:107:22: note: a field of same name but different type is defined in another translation unit
   std::n< RootData > mxRD;
                      ^
libre-1.ii:111:39: note: type ‘struct RootDataRef’ should match type ‘struct n’
   typedef std::shared_ptr< RootData > RootDataRef;
                                       ^
libre-3.ii:23:31: note: the incompatible type is defined here
 template < typename a > class n : __shared_ptr< a > {};
                               ^
lto1: internal compiler error: in get_odr_type, at ipa-devirt.c:2096
0x8d7ca7 get_odr_type(tree_node*, bool)
        ../../gcc/ipa-devirt.c:2096
0x8d7e0c register_odr_type(tree_node*)
        ../../gcc/ipa-devirt.c:2121
0x6156a0 lto_read_decls
        ../../gcc/lto/lto.c:1782
0x6178c4 lto_file_finalize
        ../../gcc/lto/lto.c:2076
0x6178c4 lto_create_files_from_ids
        ../../gcc/lto/lto.c:2086
0x6178c4 lto_file_read
        ../../gcc/lto/lto.c:2127
0x6178c4 read_cgraph_and_symbols
        ../../gcc/lto/lto.c:2839
0x6178c4 lto_main()
        ../../gcc/lto/lto.c:3356
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
make: *** [/tmp/cc6NqUBv.mk:2: /tmp/ccU4uBCo.ltrans0.ltrans.o] Error 1
lto-wrapper: fatal error: make returned 2 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status