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    SubjectRe: glibc-2.1 upgrade headaches. Any ideas??
    Arvind Sankar wrote the following:
    > On Sun, Mar 07, 1999 at 02:09:17PM +1100, CaT wrote:
    > > I've been happily doing it for a while with -O2 optimisation and
    > > -march=pentiumpro and haven't had a single kernel crash.
    > >
    > > I'd use -O6 but I can't find any info on what the hell this does
    > > as far as optimisation goes.
    > The biggest you can go to currently is -O3, I believe. Anything beyond that
    > turns on the same flags.

    Right. That's what I figured. But a lot of people seem to go on about how -O6
    should be used for best performace... I've found that somewhat confusing...

    > > of -O2 (I compiled X without it and it's working fine. Hasn't crashed) or
    > > is it something the kernel needs? And, what exactly does this do? I've read
    > > the manpage but what that has doesn't mean much to me. I wish there was
    > > info on not just what an optimisation flag does but also how it might effect
    > > performance and what sideeffects it might have. (this is probably real hard
    > > to do but it would be way useful. I don't mind long compile times as long
    > > as runtime performance is imporved)
    > >From the gcc manual:
    > `-fomit-frame-pointer'
    > Don't keep the frame pointer in a register for functions that
    > don't need one. This avoids the instructions to save, set up and
    > restore frame pointers; it also makes an extra register available
    > in many functions. *It also makes debugging impossible on some
    > machines.*
    > This option is never turned on by default (on i386), so the kernel Makefile
    > turns it on.

    Uhuh. Does this prevent the use of gdb on the executable and can it be
    used safely on libraries?

    > Obviously, it should improve run-time performance, unless the gcc code
    > optimizer is so buggy that it generates faster code with less registers
    > available ;)

    Hehe :)

    CaT ( URL:

    An electricity provider of New Hampshire, US has advised it's customers
    that in the event of a power failure they can log on to its website for
    more information... - Paraphrased from the New Scientist, Feb 6, 1999

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