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Old 02-10-2011, 03:22 PM
Paul Hartman
 
Default The CHOST variable

On Thu, Feb 10, 2011 at 9:24 AM, Stroller
<stroller@stellar.eclipse.co.uk> wrote:
> I don't really know what the "-fomit-frame-pointer" part does - I imagine someone suggested it, perhaps on here, years ago, and it has got copied from system to system.

I think it removes your ability to get a stack trace when programs
crash, in exchange for potentially more speed. If you're a programmer
or filing bug reports on crashing software you should not use it, I
don't think. But I could be wrong.
 
Old 02-10-2011, 04:07 PM
Stroller
 
Default The CHOST variable

On 10/2/2011, at 4:22pm, Paul Hartman wrote:

> On Thu, Feb 10, 2011 at 9:24 AM, Stroller
> <stroller@stellar.eclipse.co.uk> wrote:
>> I don't really know what the "-fomit-frame-pointer" part does - I imagine someone suggested it, perhaps on here, years ago, and it has got copied from system to system.
>
> I think it removes your ability to get a stack trace when programs
> crash, in exchange for potentially more speed. If you're a programmer
> or filing bug reports on crashing software you should not use it, I
> don't think. But I could be wrong.

Thanks!


I appreciate the informative & helpful answer.

Stroller.
 
Old 02-10-2011, 07:36 PM
Alan McKinnon
 
Default The CHOST variable

Apparently, though unproven, at 17:18 on Thursday 10 February 2011, Stroller
did opine thusly:

> On 8/2/2011, at 9:55pm, Alan McKinnon wrote:
> > ...
> > If you're a gambling man, play it by the numbers:
> >
> > A re-install for a Gentoo user with a clue is a certain 1 hour of your
> > life tops to get it redone with a recent stage 3, more likely 30
> > minutes. That will give you a working system albeit one a bit out of
> > date that emerge -avunD world will fix nicely.
>
> That makes no sense to me at all.
>
> There are stage3s built on a daily basis - they won't be out of date at
> all. But they don't include system logger, cron, locale, or any of your
> personalisations.

All I'm saying is it is often better to go the reinstall route which will take
a known amount of time for a certain result, rather than the try fix it route
which is highly variable as to how long it will take or even if it will work
at all.

It's assumed that one has backups of world and all configs, or can make
backups before starting the reinstall.

As with all things YMMV and real circumstance trumps abstract theory every
time

>
> On any kind of complex system it will take me more than a day to set those
> up - can I be sure that I'll get them right first time, every time?
>
> If we're talking about an older system then I need to back up everything so
> that I can copy files the files I missed from the /etc to the new one.
>
> If you're talking about stuff like KDE then that alone is going to take
> more than an hour to compile.
>
> I understood that a backup that was of your own system - that might be a
> bit out of date but which includes these things - was called a stage4. And
> in that case you're still faced with the problem that it's probably just
> as out of date as the install which is proving difficult to update in the
> first place.
>
> My experience of a system which was a year or even 18 months old was that
> it did have some blockers and some bugs which had been addressed here
> months before. It did require me to pull some files out of Gentoo's CVS
> attic and emerge the old ebuilds from my local tree, before they could be
> updated to current. But I knew that the configuration was sound and that
> all I had to do was address the blocker and then resume the `emerge -ud
> world`- the emerging is something that can go on in the background whilst
> I'm not paying attention.
>
> Stroller.

--
alan dot mckinnon at gmail dot com
 
Old 02-10-2011, 08:40 PM
Nils Holland
 
Default The CHOST variable

On 10:22 Thu 10 Feb , Paul Hartman wrote:

> On Thu, Feb 10, 2011 at 9:24 AM, Stroller
> <stroller@stellar.eclipse.co.uk> wrote:
> > I don't really know what the "-fomit-frame-pointer" part does - I imagine someone suggested it, perhaps on here, years ago, and it has got copied from system to system.
>
> I think it removes your ability to get a stack trace when programs
> crash, in exchange for potentially more speed. If you're a programmer
> or filing bug reports on crashing software you should not use it, I
> don't think. But I could be wrong.

Yep, that option leads to the frame pointer not being saved /
restored, making an additional register available (but obviously there
are differences between architectures; on some this option has no
effect at all). On architectures where it does have an effect, it
would make debugging impossible.

Well, after having written the last paragraph I've decided to check
out the GCC man page for more information and see: According to the
GCC man page -fomit-frame-pointer gets enabled by default when using
optimization levels -O or higher (including, of course -O2, which in
my experience is what most people seem to use).

As a matter of fact, I have -O2 but intentionally not set
-fomit-frame-pointer, not being aware that with -O2, I automatically
get it. ;-) I'll have to check out the Gentoo handbook, but if I
remember correctly, it actually suggests using -O2 but better stay
away from -fomit-frame-pointer. If it really suggests this, that might
be considered a bug I guess. ;-)

Greetings,
Nils


--
Nils Holland * Ti Systems, Wunstorf-Luthe (Germany)
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