[plug] Slow kernel compile after rebuild

[William Kenworthy]

I missed most of this thread, but are you trying to mix code compiled
with 2.95 and 3.x on the same machine?  Unless you have taken special
precautions this is a no-no.  gcc has had a number of ABI changes (2.9x,
3.0, 3.1 and 3.2 - I think), all incompatible at the ABI level giving
rise to odd crashes for simple things to a dead system when you do glibc
or other critical binary like a kernel that interacts with a lot of
other code.

For gentoo, when you change compilers you recompile the whole OS and
apps so there are no clashes - with a binary distro you are dead unless
you upgrade the lot as a whole and yes, gentoo compiles the kernel with
3.x (there's a setting for gcc>3 in the config but dont know what it
actually does in detail!)  It is possible for gcc2.95 and gcc3.x to
reside on a gentoo system in separate "slots", but only one is the
"main", the other is acting more like a cross-compiler.

gcc3+ is supposed to take longer to compile, but produce smaller, faster
and (maybe) better optimised binaries, but I think its main advantage is
it is more correct than previous versions, catching errors that previous
versions would allow through.

My take is gcc3 is heaps better than older versions, whose only
advantage is that they have been around long enough for their bugs to be
well known.  None of my current gentoo systems have gcc 2.9x left on
them, though 2 started out with it and have been upgraded.

BillK

On Thu, 2003-10-02 at 19:48, James Devenish wrote:
> In message <1065094979.8731.25.camel at localhost>
> on Thu, Oct 02, 2003 at 07:42:59PM +0800, Ryan wrote:
> > These gcc 3 speed issues you say are normal ... is this the designed
> > behaviour - if so do you know why?
> 

> That seems surprising for i386. Might not be a compiler bug per se,
> since it is possible for the kernel to contain coding errors. Not sure
> who compiles their kernel with gcc 3 -- perhaps you could inquire with
> gentoo people (hi Bill)?
> 
> 
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-- 
William Kenworthy <billk at iinet.net.au>

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