On Wed, Aug 6, 2014 at 12:08 PM, Jonathan Wakely <jwakely....@gmail.com> wrote: > On 6 August 2014 10:06, Jakub Jelinek wrote: >> On Wed, Aug 06, 2014 at 11:04:14AM +0200, Richard Biener wrote: >>> > - libstdc++ ABI changes (it is a significant user visible change, >>> > if you rebuild everything, no extra effort is needed, but otherwise >>> > if you want some C++ code built with older compilers work together >>> > with code built with newer compilers, it might require source code >>> > changes (the abi_tag attribute additions where needed and warning >>> > suggest to put those at), at least that is my current understanding >>> > of the plans >>> >>> But that's only with -std=c++11? Which had no compatibility >>> guarantees before? >> >> No, AFAIK it is also -std=c++98. At least my understanding was that >> std::list and std::string are going to change ABI (and get new abi_tag) >> in all C++ modes. Jonathan/Jason/Paolo, is that right? > > Correct. We want C++03 code to continue to be able to interoperate > with C++11 code. > > It's an ABI change for all modes (but not a SONAME change because the > old and new definitions will both be present in the .so).
Ugh. That's going to be a nightmare to support. Is there a configure switch to change the default ABI used? That is, on a legacy system can I upgrate to 5.0 and get code that interoperates fine with code built with 4.8? (including ABI boundaries using the affected classes? I suspect APIs with std::string passing are _very_ common, not sure about std::list) What's the failure mode the user will see when linking against a 4.8 compiled library with a std::string interface using 5.0? Thanks, Richard.