Default ISA/tuning flags for GCC, --enable-kernel= level for glibc

[Kyle McMartin]

On Mon, Jan 26, 2009 at 11:15:01AM +0100, Jakub Jelinek wrote:
> Another question is if we finally could bump the minimum supported kernel
> version in Fedora 11 glibc.  Currently Fedora 10 glibc requires 2.6.9 or
> later kernel, which means it can't assume a lot of stuff (e.g. private
> futexes, a lot of added syscalls etc.), which means it has to test for them
> at runtime of every program (e.g. every threaded program does a dummy futex
> syscall to check for private futexes, for futex realtime clock support and
> has to use variables for this, instead of oring constants in the mutexes
> etc., and glibc has to check for ENOSYS and have fallbacks compiled in).
> 2.6.9 default comes I think still from the RHEL4 kernels.
> Could we bump this ideally to 2.6.29?  It would mean Fedora 11 userland
> only runs on 2.6.29 and later kernels, but we could gain speed and decrease
> size of glibc shared libraries.
> 

No. No. No.

No. No.

No.

Breaking userspace for anyone attempting to bisect a regression?

Get real. You owe your users better than that.

Ship two copies of glibc and decide at runtime, but a hardcoded limit
is just BROKEN software design.

regards, Kyle