Re: [PATCH 1/3] libstdc++: Add time_get::get support.

[Jonathan Wakely <jwakely at redhat dot com>]

On 16/04/14 13:19 +0200, Rüdiger Sonderfeld wrote:
> On Tuesday 15 April 2014 23:36:51 Paolo Carlini wrote:
> > Those should be isolated and a compiler bug report opened including a
> > minimized reproducer.
>
> I'm not sure if this is a compiler bug or simply due to the fact that I didn't
> add the virtual function to the ABI linker script.
>
> > Anyway, the real issue is indeed that implementing those bits requires a
> > new virtual function, and that would break the ABI. We do have a bug in
> > Bugzilla tracking the issue.
>
> But now that 4.9 has branched isn't it acceptable to extent the ABI?

Adding new virtual functions does not "extend" the ABI, it makes it
incompatible. We either need to change the library's SONAME (not
acceptable to some GNU/Linux dsitributions) or mangle the type
differently so it is a new type for linkage purposes (which is what we
plan to do using the abi_tag attribute).