Gentoo compile flags - Revision history

Flow: /* Which flags to use */

2011-07-24T09:18:41Z

‎Which flags to use

Rwald: /* Which flags to use */

2008-02-21T11:02:09Z

‎Which flags to use

Rwald: /* Example files */

2008-02-21T11:01:38Z

‎Example files

Rwald: Updated CFLAGS section with new info

2008-02-21T11:00:51Z

Updated CFLAGS section with new info

Vitaliy: /* Which flags to use */

2006-04-19T23:11:22Z

‎Which flags to use

80.220.48.208: /* Example files */

2005-11-19T09:22:53Z

‎Example files

80.197.65.56: /* Which flags to use */

2005-11-01T19:35:16Z

‎Which flags to use

Wyrfel at 16:13, 14 July 2005

2005-07-14T16:13:18Z

192.33.106.228 at 14:59, 30 March 2005

2005-03-30T14:59:17Z

192.33.106.228 at 22:11, 14 March 2005

2005-03-14T22:11:22Z

New page

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<div style="margin: 0; margin-right:10px; border: 1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#F8F8FF; align:right;">
=== Gentoo compile flags ===
This page gives an introduction to Gentoo compile flags.
</div>
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{| style="vertical-align:top;margin-left:20px;margin-right:20px"
|
__NOTOC__
=== About compile flags in Gentoo ===
One strength of Gentoo is the ability to use global flags for code optimizing. This is done through the file /etc/make.conf ([http://gentoo-wiki.com/MAN_make.conf_5 man page]). Since the Pentium Mobile (Centrino) used in some Thinkpads supports the mmx and sse extensions of the insturuction set, using compile flags can speedup programs quite a bit. To use optimized code, you have to adjust the USE ([http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=2&chap=2 Gentoo Handbook]) variable, which contains the libraries and extensions you want to use and the CFLAGS variable, which contains compiler flags, that portage passes along to gcc.

If you want to set specific flags for only one package, you can also use the file /etc/portage/package.use instead of the USE variable in make.conf.

=== Which flags to use ===
In order to adjust USE correctly, you have to find out, which instruction set extensions your processor supports. The Pentium M instruction set is compatible to a Pentium 4 and supports mmx and sse extensions, so your make.conf should contain something like this:

USE="mmx mmx2 sse sse2"
CFLAGS="-O2 -march=pentium4 -pipe -fomit-frame-pointer"

You might also use -O3, but it may cause crashes in your programs if you optimize too much.
Independently of the CPU it's also a good idea to tell portage which libraries to use. If you leave away all the libraries you don't need, you can save compile time, get a smaller binary size and faster programs.

For instance, if you know you don't use Gnome and don't need java support in you binaries, but you want to use KDE, your make.conf might contain
USE="mmx mmx2 sse sse2 qt kde -gnome -java"
If you want gnome support in your binaries at any later time, you just have to edit make.conf an run "emerge --newuse world" (this will take some time though).

=== Example files ===
These are the make.conf and package.use files I use for my T40P:
*make.conf
USE="X mmx mmx2 sse sse2 qt kde -gpm -gtk -gtk2 -gnome -arts -alsa -cups -java -esd -v4l -v4l1 -samba -ipv6 -directfb -lirc -svga"
CFLAGS="-O2 -march=pentium4 -pipe -fomit-frame-pointer"
CHOST="i686-pc-linux-gnu"
CXXFLAGS="${CFLAGS}"
MAKEOPTS="-j2"

*package.use
sys-libs/glibc userlocales
app-laptop/tpb xosd
media-video/mplayer dvd xanim divx4linux network xvid live
media-libs/xine-lib dvd

|}

=== Other portage features ===
There are lots of other great features in portage (the Gentoo package managing system). If you want to use Gentoo, you should read the docs on [http://gentoo.org gentoo.org] and the man pages of portage and make.conf.

[[Category:Gentoo]]

@@ Line 16: / Line 16: @@
 === Which flags to use ===
-Gentoo has a [http://gentoo-wiki.com/Safe_Cflags separate wiki page] for deciding which CFLAGS are right for you. Use your model's page here at ThinkWiki to figure out your processor family, then look it up on that page for the proper CFLAGS. That page may assume that you're using GCC version 4.2, but this is the case on all reasonably modern systems.
+Gentoo has a [http://en.gentoo-wiki.com/wiki/Safe_Cflags separate wiki page] for deciding which CFLAGS are right for you. Use your model's page here at ThinkWiki to figure out your processor family, then look it up on that page for the proper CFLAGS. That page may assume that you're using GCC version 4.2, but this is the case on all reasonably modern systems.
 Additionally, it may help to include ''some'' of the following USE flags:

@@ Line 18: / Line 18: @@
 Gentoo has a [http://gentoo-wiki.com/Safe_Cflags separate wiki page] for deciding which CFLAGS are right for you. Use your model's page here at ThinkWiki to figure out your processor family, then look it up on that page for the proper CFLAGS. That page may assume that you're using GCC version 4.2, but this is the case on all reasonably modern systems.
-Additionally, it may help to include some of the following USE flags:
+Additionally, it may help to include ''some'' of the following USE flags:
   USE="mmx sse sse2 ssse3"

@@ Line 39: / Line 39: @@
   media-libs/xine-lib dvd
-This is the make.conf files used for a 64-bit T61 (with Intel X3100 graphics):
+This is the make.conf file used for a 64-bit T61 (with Intel X3100 graphics):
 *make.conf
   CFLAGS="-march=nocona -O2 -pipe"

@@ Line 16: / Line 16: @@
 === Which flags to use ===
-In order to adjust USE correctly, you have to find out, which instruction set extensions your processor supports. You can use google for this, or look at /proc/cpuinfo. If you are using an older version of GCC (below 3.4) you should use:
+Gentoo has a [http://gentoo-wiki.com/Safe_Cflags separate wiki page] for deciding which CFLAGS are right for you. Use your model's page here at ThinkWiki to figure out your processor family, then look it up on that page for the proper CFLAGS. That page may assume that you're using GCC version 4.2, but this is the case on all reasonably modern systems.
- CFLAGS="-O2 -march=pentium4 -pipe -fomit-frame-pointer"
+Additionally, it may help to include some of the following USE flags:
-You might also use -O3, but it may cause crashes in your programs if you optimize too much.
+ USE="mmx sse sse2 ssse3"
-With either GCC version you should be using the following USE flags:
+Run the command "cat /proc/cpuinfo" and look through the "flags" section to see which your CPU supports; only include those in your global USE flag.
 === Example files ===
-These are the make.conf and package.use files I use for my T40P:
+These are the make.conf and package.use files used for a T40P:
 *make.conf
   USE="X mmx mmx2 sse sse2 qt kde -gpm -gtk -gtk2 -gnome -arts -alsa -cups -java -esd -v4l -v4l1 -samba -ipv6 -directfb -lirc -svga"
@@ Line 45: / Line 38: @@
   media-video/mplayer dvd xanim divx4linux network xvid live
   media-libs/xine-lib dvd
 === Other portage features ===

@@ Line 16: / Line 16: @@
 === Which flags to use ===
-In order to adjust USE correctly, you have to find out, which instruction set extensions your processor supports. You can use google for this, or look at /proc/cpuinfo. The Pentium M instruction set is compatible to a Pentium 4 and supports mmx and sse extensions, so your make.conf should contain something like this:
+In order to adjust USE correctly, you have to find out, which instruction set extensions your processor supports. You can use google for this, or look at /proc/cpuinfo. If you are using an older version of GCC (below 3.4) you should use:
   CFLAGS="-O2 -march=pentium4 -pipe -fomit-frame-pointer"
-If you have a Pentium-M cpu you should use "-march=pentium3" since it's a Pentium 3 deriviate, unless you're using GCC >=3.4 which is marked as unstable. GCC 3.4 has a specific march-setting for Pentium-M machines.
+As of >=3.4 release of GCC Pentium-M CFLAGs are supported and the following should be used:
 You might also use -O3, but it may cause crashes in your programs if you optimize too much.
 Independently of the CPU it's also a good idea to tell portage which libraries to use. If you leave away all the libraries you don't need, you can save compile time, get a smaller binary size and faster programs.
-For instance, if you know you don't use Gnome and don't need java support in you binaries, but you want to use KDE, your make.conf might contain
+With either GCC version you should be using the following USE flags:
-  USE="mmx mmx2 sse sse2 qt kde -gnome -java"
-If you want gnome support in your binaries at any later time, you just have to edit make.conf an run "emerge --newuse world" (this will take some time though).
+  USE="mmx mmx2 sse sse2"
 === Example files ===

@@ Line 4: / Line 4: @@
 <div style="margin: 0; margin-right:10px; border: 1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#F8F8FF; align:right;">
 === Gentoo compile flags ===
-This page gives an introduction to Gentoo compile flags.
+This page gives an introduction to {{Gentoo}} compile flags.
 </div>
 |}
@@ Line 48: / Line 48: @@
 |}