Re: [gentoo-dev] Gcc 3.0.4 installed system

[Preston A. Elder]

I'm sure it does ...

But unless I'm missing something here, changing the profile does NOTHING
to change the utilities (read: tar, bzip2, cp, mv, ls, etc) that are
installed WITH the system.

Read my email again carefully.  I manually made my own
'default-1.0-gcc3' profile by changing the packages file to use gcc3
instead of 2.95 and then bootstrapped with it -- and it worked fine
right up until it installed glibc.

Just incase your not a coder.  GLIBC supplies both C and C++ libraries
and symbols for other programs to use.  All C++ symbols are 'mangled',
which is a method the compiler uses to differentiate different functions
with the same name but different types (read up on C++ function
overloading and name mangling).

3.0 changed the mangling scheme used to mangle C++ names from what was
used with 2.x -- which means, quite simply, if you have an application
thats been compiled against libraries built with gcc 2.x, and then you
compile the libraries with 3.x, the application will cease to work,
because it will not be able to find the symbols it needs to run. 
Usually, this will result in a core dump.  This only affects programs
written in C++.

This is exactly what happens with utilities such as tar, which is
written in C++ (which surprised me).  Which is why, your
default-1.0-gcc3 profile will *NOT* enable someone to bootstrap with gcc
3.0, unless you happen to have a stage1 ISO that has statically linked
binaries in it (theoretically, if you have statically linked binaries on
the whole system, you dont even NEED a /lib or /usr/lib directory,
because its all statically linked).

This was the point I was trying to make.  Dont get me wrong, I'm glad
the gcc3 profile is there, and I'm using it, because I use gcc3
exclusively -- however gcc3 (for now), is only available as a
POST-bootstrap (ie. stage2) compilation, until we get a 1.0 ISO with
statically linked binaries -- or binaries that are still dynamically
linked, but all compiled with gcc3.0 against a glibc compiled with
gcc3.0.  Which brings in the chicken and the egg problem.

This is also why you will have to lock people into a specific glibc
version in your gcc3 profile (which I've noticed you dont do right
now).  Say someone bootstraps as normal, then installs gcc3, then
switches to your gcc3 profile, and continues to build the system.  If,
at some later point, a new revision or version of glibc comes out, and
is put into the portage tree, and the user then does a world upgrade,
they will attempt to re-compile glibc.  It will compile, but as soon as
it installs, a good proportion of the rest of their system will stop
working for exactly the reason I described.  I've manually locked my
glibc version because of this fact, because I know I cant re-compile it
with gcc3 without breaking my system.

If I get time, I'll sit down and think about how to actually create a
stage1 (the thing you tar -xvbjf onto your hard disk) system that is
totally gcc3 based, or see if I can create a stage1 with all statically
linked binaries in it.  For now, thats not high on my priority list.

On Sun, 2002-04-07 at 06:14, Geert Bevin wrote:
> Changing the profile in /etc/make.profile to default-1.0-gcc3 should
> make you bootstrap against gcc3 instead.
>
> On Sun, 2002-04-07 at 05:29, Preston A. Elder wrote:
> > Personally, I'd be very interested to know how you did this 'from
> > scratch'.
> >
> > I myself have done this from the post-bootstrap (but pre emerge system)
> > stage on, but I cant bootstrap with 3.0.x, why?
> >
> > Well, the image the ISO installs has many applications on it, not linked
> > statically (eg. tar, etc) -- compiling gcc3.0.4 works fine, but as soon
> > as it then compiles glibc 2.2.5 and installs it, nothing else works.
> >
> > The utilities on the install image look for glibc 2.2.5 compiled with
> > gcc 2.95.x.  So until there is an install image that has statically
> > linked binaries on it, I dont see how a bootstrap can be achieved using
> > 3.0.x compilers.
> >
> > I too, however, have installed a 3.0.x based system.  I did the
> > bootstrap on 2.95.3, then first thing after bootstrap, I merged gcc
> > 3.0.4, and then did my emerge system.  As Geert said, a few problems
> > along the way, but not many.  I too made patches for all the problems I
> > found, I submitted them to Geert.  The patches I made are ALL backward
> > compatable to 2.95.3 (I believe, I've not tested this).  But then, I
> > could also have compiled a different package set than he did.
> >
> >
> > On Sat, 2002-04-06 at 07:01, Geert Bevin wrote:
> > > Hi all,
> > >
> > > I finally installed 1.0 from scratch and decided to try it out with gcc
> > > 3.0.4 instead of 2.95.3. Along the way I encountered some problems, but
> > > surprisingly little. I've fixed everything that needed fixing and sadly
> > > some packages are backwards incompatible. For that reason and for the
> > > ease of maintenance I've created a dedicated gcc 3 profile.
> > >
> > > So, for those that want to try this out, just link the default-1.0-gcc3
> > > profile instead of default-1.0 to /etc/make.profile. Note that this will
> > > only work for installations from scratch and not for updates since
> > > applications that link against libstdc++ v2 require the libraries of gcc
> > > v2 and not gcc v3.
> > >
> > > There are still some packages that don't compile such as galeon and
> > > openjade, but these will be fixed in a matter of time since I need them
> > > ;-) Feel free to submit fixes too.
> > >
> > > Best regards,
> > >
> > > Geert Bevin
> > > --
> > > Geert Bevin             Uwyn
> > > "Use what you need"     Lambermontlaan 148
> > > http://www.uwyn.com     1030 Brussels
> > > gbevin@××××.com         Tel & Fax [phone]
> > >
> > > _______________________________________________
> > > gentoo-dev mailing list
> > > gentoo-dev@g.o
> > > http://lists.gentoo.org/mailman/listinfo/gentoo-dev
> >
> > Thanks,
> >
> > --
> > PreZ
> > Systems Administrator
> > GOTH.NET
> >
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> >
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> --
> Geert Bevin             Uwyn
> "Use what you need"     Lambermontlaan 148
> http://www.uwyn.com     1030 Brussels
> gbevin@××××.com         Tel & Fax [phone]
>
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PreZ
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