On Thu, Mar 24, 2016 at 6:54 AM, Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx> wrote: > On 2016.03.24 at 06:50 -0400, Jeffrey Walton wrote: >> We caught a report due to _GLIBCXX_USE_CXX11_ABI and abi:cxx11. We are >> upstream, and it appears Debian built the library using GCC and >> _GLIBCXX_USE_CXX11_ABI was in effect. A user then came along with >> Clanf and compiled the userland program. The link failed. This is >> expected given our understanding of the landscape. >> >> We found "GCC5 and the C++11 ABI", >> https://developerblog.redhat.com/2015/02/05/gcc5-and-the-c11-abi/. The >> pages says: >> >> Providers of such libraries or interfaces need to consider >> whether they want to provide ABI coexistence, like libstdc++ >> does, or require their users to rebuild. >> >> I read the Red Hat blog post, but its not clear to me how to >> accomplish the coexistence. That is, I want to ensure the library that >> Debian builds has a symbol in both namespace so linking can occur with >> either GCC or Clang and "things just work" for the user. >> >> How is libstdc++ providing symbols in both namespaces? How do I ensure >> the symbol is present in both namesspaces so "things just work" for a >> user? > > It will not work until this clang bug gets fixed: > https://llvm.org/bugs/show_bug.cgi?id=23529 Thanks Markus. Please forgive my ignorance... What is the "coexistence" that is discussed? Naively, I thought it would have been something like this contrived example: $ cat test.cxx #include <string> std::string foo __attribute__ ((visibility ("default"))); std::string bar __attribute__ ((visibility ("default"))); $ g++ -g3 -O2 -shared test.cxx -o test.so $ nm test.so | grep _Z3 ... 0000201c B _Z3barB5cxx11 00002034 B _Z3fooB5cxx11 $ echo _Z3fooB5cxx11 _Z3barB5cxx11 | c++filt foo[abi:cxx11] bar[abi:cxx11] foo bar In the above contrived example, foo and bar are in both namespaces. That is, the symbol coexists and "things just work". Jeff
