[gentoo-amd64] Re: Question On Linux-Headers And Glibc

[Nikos Chantziaras]

On 02/15/2010 06:45 AM, Frank Peters wrote:
> Doing my daily emerge update, I noticed that a new release of the
> linux-headers, version 2.6.32, was available.  After installing this
> new version, there appeared a message advising that glibc be re-emerged
> to take advantage of any new features that might be available in the
> latest kernel headers.
>
> My question is: why are not glibc and the linux-headers linked
> in a dependency relationship?  If re-compiling glibc after emerging
> a new version of linux-headers could be so important, why not just create
> an ebuild that will automatically do this via dependencies rather than
> provide a message that a lot of users may miss?

There's no way to force a rebuild of something through dependencies. 
Only a revision or version bump can do this.


> When glibc is emerged, I assume that only the headers from the linux-
> headers package are used and not the headers contained in the kernel
> source tree at /usr/src/linux.  Is this correct?

Depends on the user.  External kernel modules always use the headers 
from /usr/src/linux.  User-space programs use the header from the 
linux-headers package.


> Also, what programs, when emerged, would directly use any kernel headers?
> I assume only programs that need to access hardware directly through
> kernel functions would need to use these headers.  Of course glibc calls
> the kernel directly, but the only other programs that would need to do
> so would deal with video or sound or something similar.  Is this correct?

As explained above, user-space uses linux-headers.  /usr/src/linux is 
used for building kernel modules.  To give examples, 
x11-drivers/ati-drivers and app-emulation/vmware-modules use 
/usr/src/linux (kernel sources package), while media-libs/alsa-lib and 
sys-libs/glibc would use /usr/include/linux (linux-headers package).