Re: [gentoo-dev] Gcc 3.0.4 installed system

[Preston A. Elder]

GCC 3.0 is more standards adhering.

GCC 2.95.3 is faster (to compile) because they dont enforce certain
coding standard (eg. ANSI, etc).  There are many things you can get away
with in GCC 2.95 that 3.0 wont let you get away with.

Thats what a lot of the extra compile time is doing in 3.0 -- ensuring
that your adhering to the standards for C/C++ -- which usually saves
your arse at debugging time.

I believe 3.0 also made a bunch of advances in optimization (including
things such as architecture specific optimizations (ala. -march=athlon),
so its working harder to make your code faster.

Finally, GCC 3.0 changed alot of things, such as the C++ ABI -- and now
they have to support both the old and new ABI's (they did this for many
reasons, and apparently, will do it again for 3.1).  Because of this,
any function reference you make, it must figure out what the old and new
version of this function are, so it can look for it in various libraries
it includes -- at link time, the version that it DIDN'T need after all
is thrown away, and it uses the version it did (which is why you can
link against a version of glibc compiled with either gcc 2.95.x or
3.0.x).

At least, this is why I THINK GCC 3.0 is slower at compiling -- as for
runtime speed, there should be little difference, and if GCC did their
job right, binaries compiled with 3.0 should actually be faster.

On Sun, 2002-04-07 at 06:02, Bart Verwilst wrote:
> Howdy
>
> Yeah, i think a gentoo-1.0-gcc3.x-ix86.iso would be great!
> Ofcourse i'm not the person to make this, not quite my area :o)
>
> And my question still remains, is gcc 3.x slower than gcc 2.95.x? :o)
>
> See ya!
>
> On Sunday 07 April 2002 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,
>
> --
> Bart Verwilst
> Gentoo Linux Developer, Desktop Team
> Gent, Belgium
> _______________________________________________
> gentoo-dev mailing list
> gentoo-dev@g.o
> http://lists.gentoo.org/mailman/listinfo/gentoo-dev
-- 
PreZ
Systems Administrator
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