>
>   I'm trying to get to the bottom of where the /usr/src/linux symlink
> should
> point to.  All the gentoo instructions say it should be to the sources for
> the current kernel, and I've read on the gentoo forums that certain
> modules
> won't work correctly without that.  However, the kernel README
> specifically
> states that the symlink should point to the headers your libraries link
> against, not the current kernel.  Should I (strictly speaking) emerge
> glibc
> after I install a new kernel?

No. The kernel headers are rather sensibly maintained by the linux-headers
(or linux26-headers) packages in portage, hence packages that are
sensitive to the kernel headers, such as glibc, will not be overly
concerned with what your "kernel du jour" happens to be.

Two exceptions I can think of to that statement are:

1) Building NPTL in glibc (that part alone seems to make use of the
headers provided by the kernel at /usr/src/linux, at least it did last
time I checked)
2) Building kernel modules outside of the tree (nvidia-kernel for instance)

Therefore, the docs are quite right. Keep /usr/src/linux as a symlink
pointing to the sources for your currently running kernel as a general
rule. You won't need to update glibc on account of building a new kernel,
however I would suggest you rebuild glibc if sys-kernel/linux-headers is
upgraded at any point :)

The latest stable versions of either package at the time of writing is:

* sys-kernel/linux-headers-2.4.21-r1
* sys-kernel/linux26-headers-2.6.8.1

_Never_ build glibc against headers that are newer than a kernel that you
intend to build and run (an unlikely event in any case). If you never use
2.4, then it is safe to migrate to linux26-headers and rebuild glibc
assuming the aforementioned caveat is born in mind.

Cheers,

--Kerin Francis Millar