This is seen in a distro upgrade, with a shared library built using GCC 6, which now fails to dynamically link, when the library is rebuilt using GCC 8.
Details in https://bugs.debian.org/911090 Jonathan pointed me to PR71712, fixing the C++ mangling. $ cat > foo.C #include <string> struct foo { operator std::string(); }; foo::operator std::string() { return "Hi"; } $ g++-8 -shared -fPIC -o libfoo.so foo.C && nm -D libfoo.so | grep foo 0000000000001136 T _ZN3foocvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEv g++-7 -shared -fPIC -o libfoo.so foo.C && nm -D libfoo.so | grep foo 000000000000115a T _ZN3foocvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEB5cxx11Ev 000000000000115a T _ZN3foocvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEv $ g++-8 -fabi-version=10 -shared -fPIC -o libfoo.so foo.C && nm -D libfoo.so | grep foo 0000000000001136 T _ZN3foocvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEB5cxx11Ev 0000000000001136 T _ZN3foocvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEv GCC 7 emits the old/compat symbol, and GCC 8 emits it when explicitly built with -fabi-version=10. This ABI change results in silent breakage, maybe in more libraries than that one. Is there a reason that this compat symbol isn't emitted anymore in GCC 8? Matthias
