Re: [gentoo-dev] toolchain meeting agenda for today 19:00 UTC #gentoo-toolchain

[Andreas K. Huettel]

Am Montag, 29. Mai 2017, 19:32:48 CEST schrieb Walter Dnes:

>
>   The irc log mentions problems with some ebuilds under some versions of
> GCC.  In a similar vein, are there any anticipated issues with binaries
> built under older GCC versions running on a system that is otherwise
> all-GCC-6.3.0?  I'm thinking of pre-built binaries like Pale Moon (from
> their website), firefox-bin, seamonkey-bin, openoffice-bin,
> libreoffice-bin, libreproject-bin, etc.

Yes, but you already should have these issues (and it's a different problem).

A] Here, we've been talking about changes in the default language standard. 
-- GCC up to 5.* defaults to -std=gnu98, while GCC 6 defaults to -std=gnu14
-- ICU 59 >requires< its reverse dependencies to build with at least -std=c+
+11
-- So all packages that a) use gcc-4 or gcc-5, and b) do not in the ebuild 
"manually" add something like -std=c++11 or -std=c++14 or -std=gnu14 will fail 
to *build*.

B] What you are talking about is a change in the ABI, the binary interface of 
the libraries. That happened as well (when gcc-5.4 was stabilized), and was 
the reason for the "rebuild your stuff" newsitem.
-- GCC-5 and later internally has a different representation of C++ stuff, 
compared with gcc-4
-- Building a library with gcc-4, and an executable that links to it with 
gcc-5, or vice versa, may fail with "missing symbols".
-- If you have a binary app built with gcc-4, and your libraries e.g. are 
built with gcc-5, you may run into the same problem (and your app won't 
start). 
-- This is why e.g. unbundling of libraries in vmware-workstation was at some 
point not possible anymore.
-- I don't know of any workaround.

HTH

-- 
Andreas K. Hüttel
dilfridge@g.o
Gentoo Linux developer (council, perl, libreoffice)