(In reply to comment #26) > (In reply to comment #25) > > 3. The problem only started because distros have chosen GCC 5 as their > > default compilers for the current releases, which defaults to C++11. > > No gcc-5 doesn't default to C++11 and the issue here has nothing to do with > C++98 vs. C++11. > > Please try to get the facts strait, before posting long misleading replies.
It is related to C++11; afaik one of the reasons to break the ABI was to become C++11 standard compliant; also the new classes are tagged "cxx11". (In reply to comment #28) > The incompatibility was introduced by gcc's "automatic tagging of functions > and variables with tagged types where the tags are not already reflected in > the mangled name". > > Now every library function with e.g a std::string return type causes linker > errors. > > To solve this issue, Clang only would have to implement the return type ABI > tagging. All other ABI tags are irrelevant AFAIK. "Only" sounds like it would be easy and obvious. Sadly, this is not a trivial problem. The change was necessary to support dual-abi in one binary; you need to be able to distinguish different ABIs in the return type. (In reply to comment #29) > The relevant issue is whether libstdc++'s _GLIBCXX_USE_CXX11_ABI is enabled > by default, see > <https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html>. Yes. All distributions have the choice not to enable it by default in the first place. (In reply to comment #30) > (In reply to comment #28) > > To solve this issue, Clang only would have to implement the return type ABI > > tagging. All other ABI tags are irrelevant AFAIK. > > If I read correctly, one of the emails says this is only temporary, and > wouldn't show in the final object, since C++ doesn't distinguish return > types, that's most useful. No, it is not temporary. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to llvm-toolchain-3.6 in Ubuntu. https://bugs.launchpad.net/bugs/1488254 Title: clang++ no longer ABI-compatible with g++ Status in LLVM: Confirmed Status in llvm-toolchain-3.6 package in Ubuntu: Confirmed Bug description: $ cat foo.cc #include <string> std::string hello = "Hello, world!\n"; $ cat bar.cc #include <string> #include <iostream> extern std::string hello; int main() { std::cout << hello; return 0; } $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out Hello, world! $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out Hello, world! $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out /tmp/bar-34fb23.o: In function `main': bar.cc:(.text+0x14): undefined reference to `hello' clang: error: linker command failed with exit code 1 (use -v to see invocation) $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out /tmp/ccqU38Mh.o: In function `main': bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]' collect2: error: ld returned 1 exit status In practice, this means that many programs using C++ libraries other than libstdc++ fail to compile with clang++. For example, mosh fails with undefined references to google::protobuf::internal::empty_string_, google::protobuf::MessageLite::InitializationErrorString() const, and google::protobuf::MessageLite::SerializeAsString() const. To manage notifications about this bug go to: https://bugs.launchpad.net/llvm/+bug/1488254/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
