Re: [gentoo-dev] Re: RFC: News item regarding c++98 vs c++11

On 10/24/14 7:29 PM, Anthony G. Basile wrote:
> So I don't have to keep email the entire item to the list, how about
> just adding it as follows:
>
> "Nor is c++11 code compiled with gcc-4.7 ABI-compatible with c++11
> compiled with 4.8, and vice versa.  An example can be see in ref.
> [2]"
>
> Ref. [2] https://bugs.gentoo.org/show_bug.cgi?id=513386

I think this could still be clearer about the user/sysadmin perspective
more than a developer perspective, i.e. present this more like "both
gcc-4.7 and 4.8 installed with 4.7 being active" than "not
ABI-compatible with C++11 compiled with 4.8".

Here's my suggested draft:

-----%<----- CUT HERE -----%<-----
GCC 4.7 introduced the new experimental 2011 ISO C++ standard [1].

Users that wish to try enabling C++11 globally (e.g. using CXXFLAGS)
should exercise caution because it is not ABI-compatible with C++98.
Packages which are self-contained or do not link against any libraries
written in C++ are not affected. Note that some packages like
www-client/chromium and net-libs/webkit-gtk among others are already
using C++11 features.

Even having different versions of gcc installed simultaneously might
lead to problems, especially if the active version of gcc is older.
Please see [2] for example known bug with webkit-gtk. It is recommended
to set the latest installed version of gcc as active; some packages may
work when an older version is selected, but GCC upstream provides no
guarantees of C++11 ABI stability for code compiled with gcc-4.x and 4.y
for any x != y [3].

Ref.
[1] http://www.stroustrup.com/C++11FAQ.html
[2] https://bugs.gentoo.org/show_bug.cgi?id=513386
[3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61758
-----%<----- CUT HERE -----%<-----

Paweł