[Bug libstdc++/66145] New: std::ios_base::failure objects thrown from libstdc++.so use old ABI

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66145

            Bug ID: 66145
           Summary: std::ios_base::failure objects thrown from
                    libstdc++.so use old ABI
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: ABI
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
                CC: doko at gcc dot gnu.org
  Target Milestone: ---

Using the new cxx11 ABI in GCC5 (and trunk) the exception here isn't caught:

#define _GLIBCXX_USE_CXX11_ABI 1
#include <fstream>
#include <limits>

int main()
{
  std::fstream f;
  f.exceptions(std::ios::badbit);
  try {
    f.pword(std::numeric_limits<int>::max());
  } catch (const std::ios_base::failure&) {
    return 0;
  }
  throw 1;
}


terminate called after throwing an instance of 'std::ios_base::failure'
  what():  ios_base::_M_grow_words is not valid
Aborted (core dumped)

This is because src/c++11/functexcept.cc has:

// We don't want to change the type thrown by __throw_ios_failure (yet?)
#define _GLIBCXX_USE_CXX11_ABI 0

I actually planned to change it for GCC5 but missed it. If we change the ABI
used to compile functexcept.cc then the code above would fail when using the
old ABI instead.

One option to make both forms work would be to hack the EH runtime to make
handlers for std::ios_base::failure able to catch
std::ios_base::failure[abi:cxx11] objects, and vice versa, creating an object
of the other type on the fly.