Pierre Labastie wrote:
Le 15/05/2015 20:38, Ken Moffat a écrit :
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.
Agreed. Sounds like a good solution.
Thanks, I'll do that.
Pierre, note that I'm testing a patch for gcc right now. You may want to hold
off until I get that done. It should be in a few hours.
-- Bruce
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