On Mon, 2023-08-14 at 18:18 +0800, Yujie Yang wrote: > On Mon, Aug 14, 2023 at 03:48:53PM +0800, Xi Ruoyao wrote: > > On Mon, 2023-08-14 at 15:37 +0800, Yujie Yang wrote: > > > On Mon, Aug 14, 2023 at 01:38:40PM +0800, Xi Ruoyao wrote: > > > > On Mon, 2023-08-14 at 11:57 +0800, Yang Yujie wrote: > > > > > > > > > However, for LoongArch, we do not want such a "toplevel" library > > > > > installation since the default ABI may change. We expect all > > > > > multilib variants of libraries to be installed to their designated > > > > > ABI-specific subdirs (e.g. base/lp64d) of the GCC libdir, so that > > > > > the default ABI can be configured arbitrarily (with --with-abi) > > > > > while the gcc libdir layout stays consistent. This could be > > > > > helpful for the distribution packaging of GCC libraries. > > > > > > > > Have you tested a --disable-multilib configuration? To me with -- > > > > disable-configuration everything should be still in the toplevel > > > > directory, not any sub-directory. > > > > > > That's a good point, sorry I missed --disable-multilib here. > > > > > > However, you don't really need --disable-multilib since > > > the libraries are only built once in the default ABI configuration > > > as long as --with-multilib-list does not request anything more than > > > that. > > > > > > Maybe we should force-enabling multilib in all cases. > > > > I really don't like this. Why must I always remind my self "hey, this > > is LoongArch, there is a different directory layout" when I don't need > > multilib at all? > > > > AFAIK, the two main uses of the multisubdir layout are in the C++ > header directory and the GCC libdir (where libgcc.a resides), respectively. > The GCC libdir is fine since they are private to a user's GCC build. > However, the C++ header directory is shared across the system unless > an alternative sysroot is chosen, so the consisentency of the multilib > layout matters.
The C++ header directory should also be considered private to the GCC build. AFAIK no distro supports "overwriting a part of the system", so you cannot just install a custom GCC build and overwrite the system C++ header directory. For a cross compiler, the C++ header directory is $prefix/$target_triple/include/c++/$gcc_version/$multi_dir, the C++ header in $sysroot/usr/include/c++ (if it ever exists) will not be used at all. > So theoretically, the toplevel libraries should have the same ABI under > the the target triplet. However, for many architectures, the > "--with-abi + MULTILIB_DEFAULT" scheme may cause the toplevel to be > configured to have different meanings. https://gcc.gnu.org/PR104085 is an example of the issue caused by the different meaning. > So I think it's also a reasonable approach that we just simply eliminate > the ambiguous toplevel libraries and use a symmetric layout instead. I don't like the inconsistency among different GCC ports. If all ports use the same approach I'll not object. -- Xi Ruoyao <xry...@xry111.site> School of Aerospace Science and Technology, Xidian University
