On Wed, Aug 06, 2014 at 11:04:14AM +0200, Richard Biener wrote: > On Wed, Aug 6, 2014 at 10:48 AM, Jakub Jelinek <ja...@redhat.com> 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? > > > - likely libgfortran ABI changes (different array descriptors) > > Let's wait and see ... > > We'll find a good reason to bump the major with every release. > Like for 4.9 LTO defaults to slim-objects, or C++ rejecting even more > invalid code, or libstdc++ header re-orgs, or defaulting to dwarf4+ > (or even support for it), or VTA, or ... > > Where do we set the barrier? GCC isn't a C++ (or Fortran) compiler > only. > > So if we change to 5.1 (please not .0) then let's switch the default > optimization level to -O2! _That's_ a user-visible change across > the board.
I'm planning to move the default C standard from gnu90 to gnu11 (Currently it's blocked on the -Wc90-c99-compat warning). That's a pretty big user-visible change as well, I suppose. Marek