Linking problems due to symbols with abi::cxx11?

Question

We recently caught a report because of GCC 5.1, libstdc++ and Dual ABI. It seems Clang is not aware of the GCC inline namespace changes, so it generates code based on one se

Answer 1

Here's one way to do it, but its not very elegant. Its also not clear to me how to make GCC automate it so I don't have to do things twice.

First, the example that's going to be turned into a library:

$ cat test.cxx
#include 

std::string foo __attribute__ ((visibility ("default")));
std::string bar __attribute__ ((visibility ("default")));

Then:

$ g++ -D_GLIBCXX_USE_CXX11_ABI=0 -c test.cxx -o test-v1.o
$ g++ -D_GLIBCXX_USE_CXX11_ABI=1 -c test.cxx -o test-v2.o

$ ar cr test.a test-v1.o test-v2.o
$ ranlib test.a

$ g++ -shared test-v1.o test-v2.o -o test.so

Finally, see what we got:

$ nm test.a

test-v1.o:
00000004 B bar
         U __cxa_atexit
         U __dso_handle
00000000 B foo
0000006c t _GLOBAL__sub_I_foo
00000000 t _Z41__static_initialization_and_destruction_0ii
         U _ZNSsC1Ev
         U _ZNSsD1Ev

test-v2.o:
         U __cxa_atexit
         U __dso_handle
0000006c t _GLOBAL__sub_I__Z3fooB5cxx11
00000018 B _Z3barB5cxx11
00000000 B _Z3fooB5cxx11
00000000 t _Z41__static_initialization_and_destruction_0ii
         U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC1Ev
         U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEED1Ev

And:

$ nm test.so

00002020 B bar
00002018 B __bss_start
00002018 b completed.7181
         U __cxa_atexit@@GLIBC_2.1.3
         w __cxa_finalize@@GLIBC_2.1.3
00000650 t deregister_tm_clones
000006e0 t __do_global_dtors_aux
00001ef4 t __do_global_dtors_aux_fini_array_entry
00002014 d __dso_handle
00001efc d _DYNAMIC
00002018 D _edata
00002054 B _end
0000087c T _fini
0000201c B foo
00000730 t frame_dummy
00001ee8 t __frame_dummy_init_array_entry
00000980 r __FRAME_END__
00002000 d _GLOBAL_OFFSET_TABLE_
000007dc t _GLOBAL__sub_I_foo
00000862 t _GLOBAL__sub_I__Z3fooB5cxx11
         w __gmon_start__
000005e0 T _init
         w _ITM_deregisterTMCloneTable
         w _ITM_registerTMCloneTable
00001ef8 d __JCR_END__
00001ef8 d __JCR_LIST__
         w _Jv_RegisterClasses
00000690 t register_tm_clones
00002018 d __TMC_END__
00000640 t __x86.get_pc_thunk.bx
0000076c t __x86.get_pc_thunk.dx
0000203c B _Z3barB5cxx11
00002024 B _Z3fooB5cxx11
00000770 t _Z41__static_initialization_and_destruction_0ii
000007f6 t _Z41__static_initialization_and_destruction_0ii
         U _ZNSsC1Ev@@GLIBCXX_3.4
         U _ZNSsD1Ev@@GLIBCXX_3.4
         U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC1Ev@@GLIBCXX_3.4.21
         U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEED1Ev@@GLIBCXX_3.4.21