[Bug lto/53808] Undefined symbol when building a library with lto

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53808

--- Comment #5 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
With Jason's patch I get:

In undef.cpp we devirtualize to _ZN3fooD2Ev:
  Type: function
  Visibility: external public
  References:
  Referring:
  Function flags:
  Called by: _ZN3barD2Ev/8 (1.00 per call)
  Calls:
It is external and we expect it to be available.

In def.cpp:
_ZN3fooD2Ev/9 (foo::~foo()) @0x7f6fe5082720
  Type: function
  Visibility: external public
  References:
  Referring:
  Function flags:
  Called by: _ZN3barD2Ev/3 (1.00 per call)
  Calls:

So I correctly get undefined reference to foo destructor. It indeed seems
undefined in the testcase.

Without Jason's patch I get undefined bar destructor, that seems wrong.

Jason, I thus thunk your patch is sufficient to fix the PR. Can you commit it?