[Bug lto/56557] [4.8 Regression] Link error about `std::fstream' or `std::stringstream' with `-flto' and `-rdynamic' options

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56557

Jan Hubicka <hubicka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libstdc++                   |lto

--- Comment #14 from Jan Hubicka <hubicka at gcc dot gnu.org> 2013-03-12 12:53:17 UTC ---
This is the LTO symbol table I get out of the testcase now:
         U _ZNSdC2Ev
         U _ZNSdD1Ev
         U _ZNSdD2Ev
         U _ZNSiC2Ev
         U _ZNSiD1Ev
         U _ZNSiD2Ev
         U _ZNSoC2Ev
         U _ZNSoD1Ev
         U _ZNSoD2Ev
         U _ZNSt12__basic_fileIcED1Ev
         U _ZNSt13basic_filebufIcSt11char_traitsIcEE5closeEv
         U _ZNSt13basic_filebufIcSt11char_traitsIcEEC1Ev
         U _ZNSt13basic_filebufIcSt11char_traitsIcEED1Ev
         U _ZNSt13basic_fstreamIcSt11char_traitsIcEEC1Ev
         U _ZNSt13basic_fstreamIcSt11char_traitsIcEED1Ev
         U _ZNSt15basic_streambufIcSt11char_traitsIcEED1Ev
         U _ZNSt15basic_streambufIcSt11char_traitsIcEED2Ev
         U _ZNSt6localeD1Ev
         U _ZNSt8ios_baseC2Ev
         U _ZNSt8ios_baseD2Ev
         U _ZNSt9basic_iosIcSt11char_traitsIcEE4initEPSt15basic_streambufIcS1_E
         U _ZNSt9basic_iosIcSt11char_traitsIcEEC2Ev
         U _ZNSt9basic_iosIcSt11char_traitsIcEED1Ev
         U _ZNSt9basic_iosIcSt11char_traitsIcEED2Ev
         U _ZTTSd
         U _ZTTSt13basic_fstreamIcSt11char_traitsIcEE
         U _ZTVSd
         U _ZTVSi
         U _ZTVSo
         U _ZTVSt13basic_filebufIcSt11char_traitsIcEE
         U _ZTVSt13basic_fstreamIcSt11char_traitsIcEE
         U _ZTVSt15basic_streambufIcSt11char_traitsIcEE
         U _ZTVSt9basic_iosIcSt11char_traitsIcEE
         U _ZdlPv
         U __gxx_personality_v0
00000000 T main

So still quite a bit more than w/o LTO:

                 U _ZNSt13basic_fstreamIcSt11char_traitsIcEEC1Ev
                 U _ZNSt13basic_fstreamIcSt11char_traitsIcEED1Ev
0000000000000001 C __gnu_lto_v1
0000000000000000 T main

but the construction vtable is no longer on the list. Those extra symbols are
from virtual functions we hold for possible devirtualization.
We ought to make sure that linkers optimize out the dynamic table entries after
we are done with optimizing them out