[Bug lto/66180] [6 Regression] many -Wodr false positives when building LLVM with -flto

["trippels at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66180

--- Comment #5 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
For example:

 % cat foo1.cpp
#include <memory>
namespace {
class A {
  int i;
};
}
class G {
  std::unique_ptr<A> foo() const;
};
std::unique_ptr<A> G::foo() const { return std::make_unique<A>(); }

 % cat foo2.cpp
#include <memory>
namespace {
class A {
  bool a;
};
}
class H {
  std::unique_ptr<A> bar() const;
};
std::unique_ptr<A> H::bar() const { return std::make_unique<A>(); }

 % g++ -flto -shared -std=c++14 foo1.cpp foo2.cpp
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:102:12: warning: type
âstruct _Head_baseâ violates one definition rule [-Wodr]
     struct _Head_base<_Idx, _Head, false>
             ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:102:12: note: a
different type is defined in another translation unit
     struct _Head_base<_Idx, _Head, false>
             ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:147:13: note: the first
difference of corresponding definitions is field â_M_head_implâ
       _Head _M_head_impl;
              ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:147:13: note: a field of
same name but different type is defined in another translation unit
       _Head _M_head_impl;
              ^
foo1.cpp:3:7: note: type âstruct Aâ defined in anonymous namespace can not
match type âstruct Aâ
 class A {
        ^
foo2.cpp:3:7: note: the incompatible type defined in anonymous namespace in
another translation unit
 class A {
        ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:180:12: warning: type
âstruct _Tuple_implâ violates one definition rule [-Wodr]
     struct _Tuple_impl<_Idx, _Head, _Tail...>
             ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:180:12: note: a type
with different bases is defined in another translation unit
     struct _Tuple_impl<_Idx, _Head, _Tail...>
             ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:596:11: warning: type
âstruct tupleâ violates one definition rule [-Wodr]
     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
            ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/tuple:596:11: note: a type
with different bases is defined in another translation unit
     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
            ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:129:11:
warning: type âstruct unique_ptrâ violates one definition rule [-Wodr]
     class unique_ptr
            ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:129:11:
note: a different type is defined in another translation unit
     class unique_ptr
            ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:147:57:
note: the first difference of corresponding definitions is field â_M_tâ
       __tuple_type                                      _M_t;
                                                          ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:147:57:
note: a field of same name but different type is defined in another translation
unit
       __tuple_type                                      _M_t;
                                                          ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:146:57:
note: type âstruct __tuple_typeâ should match type âstruct __tuple_typeâ that
itself violate one definition rule
       typedef std::tuple<typename _Pointer::type, _Dp>  __tuple_type;
                                                          ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:146:57:
note: the incompatible type is defined here
       typedef std::tuple<typename _Pointer::type, _Dp>  __tuple_type;
                                                          ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:151:41:
warning: type âstruct element_typeâ violates one definition rule [-Wodr]
       typedef _Tp                       element_type;
                                          ^
/home/trippels/gcc_6/usr/local/include/c++/6.0.0/bits/unique_ptr.h:151:41:
note: a different type is defined in another translation unit
       typedef _Tp                       element_type;
                                          ^
foo1.cpp:4:7: note: the first difference of corresponding definitions is field
âiâ
   int i;
        ^
foo2.cpp:4:8: note: a field with different name is defined in another
translation unit
   bool a;
         ^