We just took a report due to http://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html
It appears Debian built the library with GCC, and GCC used _GLIBCXX_USE_CXX11_ABI. The user then compiled with Clang and caught a link error. The tools did not warn him about the problems, so the report trickled downhill to us. Would Debian please enable -Wabi-tag by default for C++ programs in its compilers. I think it can be done in a spec file for GCC. My apologies for not offering the string for the specs file. Also see http://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html. Thank you in advance.