[gentoo-user] gcc upgrade - rebuild everything?

[gentoo-user] gcc upgrade - rebuild everything?

[Grant]

I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
I really need to rebuild everything as it says in the guide:

http://www.gentoo.org/doc/en/gcc-upgrading.xml

If not, when is it necessary?

- Grant

Re: [gentoo-user] gcc upgrade - rebuild everything?

[Dale]

Grant wrote:
> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
> I really need to rebuild everything as it says in the guide:
>
> http://www.gentoo.org/doc/en/gcc-upgrading.xml
>
> If not, when is it necessary?
>
> - Grant
>
>
>    

I haven't seen any gurus recommend doing a emerge -e world in a while.  
I think that is for major changes in gcc.  The upgrade you have just 
done seems to be a minor one.

Me, if I was concerned about it at all, I would just do a emerge -e 
system.  That way you know at least the packages needed for booting is 
rebuilt.  If I have doubt, that is what I do and it doesn't take to 
long.  If you have problems with your GUI or have problems with 
programs, then you can do a emerge -e world then.

Also, if you are going to do this, there is a script that does it better 
than portage.  It emerges things in a different order so that it only 
has to be done once instead of twice.  I can find you a link to it if 
you are interested.  I used it a month or so ago and it worked fine.  
It's been around for years.

Dale

:-)  :-)

Re: [gentoo-user] gcc upgrade - rebuild everything?

[Alex Schuster]

Grant writes:

> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
> I really need to rebuild everything as it says in the guide:
> 
> http://www.gentoo.org/doc/en/gcc-upgrading.xml

The guide seems to be wrong here. Rebuilding does not harm, and it makes 
use of tall the cool new compiler optimizations, but normally it is not 
necessary.

> If not, when is it necessary?

Only when the API changes, which happened the last time when gcc went from 
3.3 to 3.4, I think.

	Wonko

Re: [gentoo-user] gcc upgrade - rebuild everything?

[Paul Hartman]

On Thu, Oct 21, 2010 at 2:58 PM, Grant <emailgrant@gmail.com> wrote:
> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
> I really need to rebuild everything as it says in the guide:
>
> http://www.gentoo.org/doc/en/gcc-upgrading.xml
>
> If not, when is it necessary?

As that guide says:

"Generally speaking, upgrades to bug fix releases, like from 3.3.5 to
3.3.6, should be quite safe -- just emerge new version, switch your
system to use it and rebuild the only affected package, libtool."

The "General Upgrade Instructions" are more for major version changes.
I don't think 4.4.3 to 4.4.4 is considered an upgrade in this sense,
just a minor update.

I think even on larger upgrade, like 4.3 to 4.4, it's only necessary
to rebuild everything if libstdc++.so's major version number has
changed. @preserved-rebuild will hopefully give some assistance in
that case anyway (if you're using a version of portage that has it).

Re: [gentoo-user] gcc upgrade - rebuild everything?

[Alan McKinnon]

Apparently, though unproven, at 21:58 on Thursday 21 October 2010, Grant did 
opine thusly:

> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
> I really need to rebuild everything as it says in the guide:
> 
> http://www.gentoo.org/doc/en/gcc-upgrading.xml

No, you do not need to do this. The document is over-reaching (see below)

I ran a mixture of 4.4.3 and 4.4.4 for ages, completely trouble-free.

> If not, when is it necessary?

When you have an ABI change in the code generated by the compiler. In other 
words, when code generated by this version is incompatible with code generated 
by that version, and you have both on the same system. This has not happened 
for a long time in gcc-land.

Now, about that official doc. Your question comes up with unbelievable 
regularity and every time the poster references that doc. But it is not 
necessary to do what the doc says, and a long time ago I think I figured it 
out.

The author's intention is less to give you the absolute complete total 100% 
truth that will always work out just fine, and more to reduce the amount of 
clutter in his inbox or on b.g.o.

The rules about how to detect when a rebuild of world is needed are complex 
and most readers simply will not understand them - they don't understand 
compiler internals (how many people DO?). But if you tell people to just 
rebuild world every time, and weird funny lurking problems are likely to just 
get fixed as a side effect, no real harm is done. Does it hurt the author? No. 
Does it reduce the amount of bugs he has to deal with on the rare occasion it 
is needed? Yes.

What does the user lose? Nothing much, more cpu cycles get used, more bits 
flip on a disk, your video card gets a work out scrolling all that text. Will 
you waste time? Yes. Will you break stuff? No.

So rebuild world if it makes you feel better. But you don't need to this time. 
The authors of gcc will certainly notify the entire world and it's dogs when 
you do need to.

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] gcc upgrade - rebuild everything?

[Grant]

>> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
>> I really need to rebuild everything as it says in the guide:
>>
>> http://www.gentoo.org/doc/en/gcc-upgrading.xml
>
> No, you do not need to do this. The document is over-reaching (see below)
>
> I ran a mixture of 4.4.3 and 4.4.4 for ages, completely trouble-free.
>
>> If not, when is it necessary?
>
> When you have an ABI change in the code generated by the compiler. In other
> words, when code generated by this version is incompatible with code generated
> by that version, and you have both on the same system. This has not happened
> for a long time in gcc-land.
>
> Now, about that official doc. Your question comes up with unbelievable
> regularity and every time the poster references that doc. But it is not
> necessary to do what the doc says, and a long time ago I think I figured it
> out.
>
> The author's intention is less to give you the absolute complete total 100%
> truth that will always work out just fine, and more to reduce the amount of
> clutter in his inbox or on b.g.o.
>
> The rules about how to detect when a rebuild of world is needed are complex
> and most readers simply will not understand them - they don't understand
> compiler internals (how many people DO?). But if you tell people to just
> rebuild world every time, and weird funny lurking problems are likely to just
> get fixed as a side effect, no real harm is done. Does it hurt the author? No.
> Does it reduce the amount of bugs he has to deal with on the rare occasion it
> is needed? Yes.
>
> What does the user lose? Nothing much, more cpu cycles get used, more bits
> flip on a disk, your video card gets a work out scrolling all that text. Will
> you waste time? Yes. Will you break stuff? No.
>
> So rebuild world if it makes you feel better. But you don't need to this time.
> The authors of gcc will certainly notify the entire world and it's dogs when
> you do need to.

Thank you everyone.  I won't rebuild.

- Grant

[gentoo-user] Re: gcc upgrade - rebuild everything?

[Nikos Chantziaras]

On 10/21/2010 10:58 PM, Grant wrote:
> I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if
> I really need to rebuild everything as it says in the guide:
>
> http://www.gentoo.org/doc/en/gcc-upgrading.xml

All libs of 4.4.3 are binary compatible with 4.4.4.  There is no need to 
rebuild.