[blfs-dev] What compatibility for BLFS development

Ken Moffat zarniwhoop at ntlworld.com
Fri May 15 11:38:21 PDT 2015

On Fri, May 15, 2015 at 10:36:36AM -0500, Bruce Dubbs wrote:
> Pierre Labastie wrote:
> >Today is slightly less busy for me and I have some time to study the new gcc 5.
> >as already noted in
> >http://lists.linuxfromscratch.org/pipermail/blfs-dev/2015-April/030081.html,
> >there is an ABI change in the libstdc++ library. The old behavior can be
> >preserved, though, because all the symbols (old and new) are contained in the
> >libstdc++.so shared object. However this is not true of other libraries built
> >using C++. The difference between old and new behavior just amounts to change a
> >#define in the header files. This can be set at build time using the switch
> >"--with-default-libstdcxx-abi" in configure.
> >
> >So:
> >a) if you have built part or all of LFS/BLFS with gcc-4.9.2, and want to update
> >to gcc-5.1.0, you need to use "--with-default-libstdcxx-abi=c++98" in order to
> >preserve the old behavior. Otherwise, newly built packages using C++ will not be
> >able to use old libraries built using C++.
> >b) if you have built from scratch using gcc-5.1.0, you need to use
> >"--with-default-libstdcxx-abi=c++11" (or nothing since it is the default).
> >
> >Now the question is: should I assume hypothesis a) or hypothesis b) for GCC in
> >BLFS? In case a), I would put the flag in the instructions and mention that it
> >can be removed in "command explanations". In case b), I would not put the flag
> >in the instructions and mention it in the "command explanations". Or put in
> >another way: should I assume that an user building BLFS-development builds upon
> >LFS-7.7, or upon LFS-development? Actually, I presently am in the first case
> >(but of course, I can rebuild to be in a second case).
> Please assume that LFS was built with gcc-5 (case b).  In addition to
> putting the switch in "command explanations", I think a <caution> explaining
> the issue just before configure would help emphasize the issue.
>   -- Bruce
Agreed.  Sounds like a good solution.

Nanny Ogg usually went to bed early. After all, she was an old lady.
Sometimes she went to bed as early as 6 a.m.

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