CFLAGS with AMD64

sl70 · Guru Joined: 18 Jun 2002 Posts: 449 Location: Saitama, JP

I'm building my system on my new AMD64 machine, and ran into a little problem. If I included -march=athlon-xp in CFLAGS, as is stated in the documentation, it got a C compiler is unable to make executables error message. So, I included only -O2 in CFLAGS. (CHOST is still x86_64 whatever.) Is that ok? Am I still going to get all the 64-bit extensions?

Thanks.

jstreed · n00b Joined: 15 Aug 2004 Posts: 3 Location: Atlanta, GA

you should set -march=athlon64

this should fix your problem.

moltonel · n00b Joined: 31 Mar 2003 Posts: 31 Location: Ireland

I've run into the same problem (C compiler unable to make executable) during bootstrap, with CFLAGS="-march=athlon64 -other-optims".

Could be an issue with gcc (I read somewhere older gcc have problems with -march=athlon64), altough I also tried with a gcc-3.4.1 stage1 tarball.

Anyway, I dropped -march from CFLAGS alltogether and it is happyly bootstraping now. If all goes well I'll try reactivating march=athlon64 after bootstarp.

crazycat · Posted: Sat Sep 04, 2004 10:42 pm Post subject:

U need gcc 3.4 to use -march=athlon64, and how to switch gcc u can find here in forum

moltonel · n00b Joined: 31 Mar 2003 Posts: 31 Location: Ireland

I used a stage1-amd64-gcc34-20040716.tar.bz2 tarball, gcc -v says 3.4.1, so does emerge, so does gcc-config -c, and I even tried using ~amd64 for gcc and gcc-config in /etc/portage/package.keywords.

I didn't check the forums, but I'm pretty confident that I'm using gcc 3.4 :p

Yet march=athlon64 doesn't work on my machine :/

LaNcom · Posted: Sun Sep 05, 2004 1:29 am Post subject:

Try "-march=k8", maybe that works...

crazycat · Posted: Sun Sep 05, 2004 3:28 am Post subject:

as u can read in gcc manual here
http://gcc.gnu.org/onlinedocs/gcc-3.4.1/gcc/i386-and-x86-64-Options.html#i386%20and%20x86-64%20Options
it should work - if not - then u do not use gcc 3.4.1 or the problem lies somewhere else! Probably, ur machine was substituted by aliens! And they uncovered the yet to be explored metaphysical misteries of gcc and the divine infinity of the infinite divinity of mystical gnu software and borked it in the way no human could ever imagine...

I use gcc 3.4.1 and -march=athlon64 myself without any problems. Maybe portage useses older gcc to compile?

moltonel · n00b Joined: 31 Mar 2003 Posts: 31 Location: Ireland

Damn those aliens

When I compile a C hello world, it works as expected (it feels good to have an athlon64-optimised hello world).
I guess it's a temporary chicken-and-egg issue. I'll tell you once I manage to put grub on the MBR, reboot, and reemerge world with march=athlon64.

moltonel · n00b Joined: 31 Mar 2003 Posts: 31 Location: Ireland

OK, whatever it was, it's solved now, and "emerge -e world" with the correct march is about finished.