[gentoo-dev] LD_ASSUME_KERNEL and duel install of nptl and linuxthreads

[Stefan Jones]

Hi,

I have recently been interested in installing the old glibc linuxthread
libraries along side the newer nptl ones.

I am considering adding this feature to gentoo.

I believe I can do this in two ways:

1) add an extra use flag to the glibc ebuild which makes a new builddir
and inside it compile the compatibility libraries. 

2) Create a new ebuild which just installs the compatibility libraries.
(glibc-compat or something)

The libs would be installed in /lib/tls or similar. On my system
LD_ASSUME_KERNEL=2.2.5 now works even though I use --enable-kernel=2.6.0
and I now have non-tls linuxthreads

I can hack the build process so it will only compile the libraries thus
speeding up the compile and install ( no nls an local stuff needs to be
rebuilt )

I would prefer option 1 as it would be easier to keep the sources in
sync, and save duplication. ( and it will then just work out of the box)

Also what needs to be considered is what the libs will enable / do,
I suggest everything RH ones do.
* Allow LD_ASSUME_KERNEL=2.2.5 to work while keeping the main libs 2.4.x
optimised ( done and tested )
* Allow fallback to linuxthreads if you have nptl installed but a 2.4.x
kernel ( RH does it - I have not tested it yet )
* (optionally) Have main libs 2.6.x optimised will fallback libs for
2.4.x if you want ( I have not got this working yet - not sure if it is
possible )

What needs to be figured out is the way this is going to be done:
/lib/libc* - This will be the optimised or fallback version, RH makes
this the fallback version
/lib/tls/libc* - the inverse of the above

/lib/ld-linux.so would have to be tls enabled I guess, I will have to
investigate how RH does it.

Are you in support of such an addition to portage? ( once it is
completed + tested )

Look forward to your comments,

Stefan
-- 
Stefan Jones <cretin@g.o>
Gentoo Linux


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