Attachment 95503 Details for Bug 145014 – Proposed changes

Proposed changes

gcc-upgrading-changed.xml (text/plain), 15.97 KB, created by Wernfried Haas (RETIRED) on 2006-08-30 12:10:12 UTC

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><?xml version='1.0' encoding="UTF-8"?>
>
>
><!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
>
><guide link="/doc/en/gcc-upgrading.xml">
><title>Gentoo Linux GCC Upgrade Guide</title>
>
><author title="Author">
> <mail link="amne@gentoo.org">Wernfried Haas</mail>
></author>
><author title="Author">
> <mail link="jkt@gentoo.org">Jan KundrÃ¡t</mail>
></author>
><author title="Editor">
> <mail link="halcy0n@gentoo.org">Mark Loeser</mail>
></author>
>
><abstract>
>This document will guide the user through the process of upgrading GCC on their
>Gentoo Linux machines.
></abstract>
>
>
>
><license/>
>
><version>12</version>
><date>2006-05-26</date>
>
><chapter id="intro">
><title>Introduction</title>
><section>
><title>GCC Upgrading</title>
><body>
>
>
>Why should you upgrade? Well, GCC is quite similar to any other package on your
>system, just a bit more critical. You should upgrade GCC whenever a new version
>fixes some bug that annoys you, new functionality you need is introduced, or if
>you want to keep your system up-to-date. If none of the previous cases apply to
>you, you can safely postpone upgrade as long as your GCC version is supported by
>Gentoo developers.
>
>
>
>If you install a newer version of GCC, the system will not switch over to use it
>automatically. You'll have to explicitly request the change because the
>migration process might require some additional steps. If you decide not to
>switch, Portage will continue to use older version of your compiler until you
>change your mind, or remove the old compiler from the system.
>
>
>
>This guide will document the necessary steps required to perform a seamless
>upgrade of the compiler used by your Gentoo box. A specific section is
>dedicated to the <uri link="#upgrade-3.3-to-3.4">upgrade from GCC 3.3 to 3.4 or
>greater versions</uri> and issues with <c>libstdc++</c>. A second specific
>section is for users <uri link="#first-install">first installing</uri> Gentoo
>using a stage3 tarball, after a new GCC major/minor version has been released.
>
>
><warn>
>It should be noted that upgrading from GCC-3.4 to GCC-4.1 or greater still
>requires you to follow the general upgrading instructions, as GCC-3.4 and
>GCC-4.1 use slightly different ABIs.
></warn>
>
></body>
></section>
></chapter>
>
><chapter id="upgrade-general">
><title>General Upgrade Instructions</title>
><section>
><title>Introduction</title>
><body>
>
><impo>
>If you're looking for instructions specific to upgrades from GCC-3.3 to GCC-3.4
>or greater, please consult the <uri link="#upgrade-3.3-to-3.4">dedicated
>section</uri>.
></impo>
>
><impo>
>If you're looking for instructions specific to upgrades in GCC for new
>installs, please consult the <uri link="#first-install">dedicated
>section</uri>.
></impo>
>
>
>Generally speaking, upgrades to <e>bug fix releases</e>, 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, <c>libtool</c>. However, some GCC
>upgrades break binary compatibility; in such cases a rebuild of the affected
>packages (or even whole toolchain and system) might be required.
>
>
>
>When we spoke about the need to switch your compiler to the newer version by
>hand, we said it won't happen automatically. However, there is one exception --
>upgrades to bug fix releases, like from 3.3.5 to 3.3.6 in case you don't use the
>"multislot" feature allowing them to coexist on one system. Multislot is
>disabled by default as the majority of users won't benefit from it.
>
>
><pre caption="Upgrading GCC">
># emerge -uav gcc
>
><comment>(Please substitute "i686-pc-linux-gnu-4.1.1" with the GCC
>version and CHOST settings you've upgraded to:)</comment>
># gcc-config i686-pc-linux-gnu-4.1.1
># source /etc/profile
>
><comment>If you upgraded from gcc 3 to 4 (e.g. from 3.4.6 to 4.1.1 in this
>example) you will have to run fix_libtool_files.sh manually</comment>
># fix_libtool_files.sh 3.4.6
>
><comment>(Rebuilding libtool)</comment>
># emerge --oneshot -av libtool
></pre>
>
>
>To be completely safe that the system is in a sane state, it is necessary to 
>rebuild toolchain and then world to make use of the new compiler. 
>
>
><pre caption="Rebuilding system">
># emerge -eav system
># emerge -eav world
></pre>
>
>
>It is safe to remove the older GCC version at this time. If you feel the need,
>please issue the following command (as usual, substitute
><c>=sys-devel/gcc-3.4*</c> with the version you want to uninstall):
>
>
><pre caption="Removing older GCC version">
># emerge -aC =sys-devel/gcc-3.4*
></pre>
>
></body>
></section>
></chapter>
>
><chapter id="upgrade-3.3-to-3.4">
><title>Upgrading from GCC-3.3 to 3.4 or greater</title>
><section>
><title>Introduction</title>
><body>
>
>
>The upgrade from GCC-3.3 to 3.4 or greater is not seamless as the C++ ABI
>changed between these two versions. There is an issue with the <c>libstdc++</c>
>library which must be taken care of, as well.
>
>
></body>
></section>
><section id="upgrade-3.3-to-3.4-choices">
><title>The Choices</title>
><body>
>
><impo>
>If you upgrade from gcc 3.4 to 4.1, please consult the General Update
>instructions.
></impo>
>
><impo>
>If you're upgrading on a SPARC machine, you will have to take the way of
><uri link="#upgrade-3.3-to-3.4-emerge-e">complete system rebuild</uri> due to
>some internal <uri link="http://gcc.gnu.org/gcc-3.4/sparc-abi.html">ABI
>changes</uri> in GCC's parameter passing.
></impo>
>
>
>If you upgrade from gcc 3.3 to 3.4, you have two possibilities on how to
>upgrade your system. The <uri link="#upgrade-3.3-to-3.4-revdep-rebuild">first
>method</uri> is faster and requires use of the <c>revdep-rebuild</c> tool from
>package <c>gentoolkit</c> while the <uri
>link="#upgrade-3.3-to-3.4-emerge-e">second one</uri> rebuilds the entire
>system from scratch so it will make use of new GCC features. It's up to you to decide which of these two ways you will choose. In most cases, the first
>method is sufficient.
>If you upgrade from gcc 3.3 to 4.1, do not use the method based on
>revdep-rebuild, but do a <uri link="#upgrade-3.3-to-3.4-emerge-e">complete
>system rebuild</uri>.
>
>
></body>
></section>
><section id="upgrade-3.3-to-3.4-revdep-rebuild">
><title>Using revdep-rebuild</title>
><body>
>
>
>This method requires that you first install <c>gentoolkit</c> if you have not
>already done so. Then we will upgrade GCC and switch to the new compiler. We
>will also rebuild the <c>libtool</c> package to ensure that toolchain is in
>healthy state.
>
>
><pre caption="Installing gentoolkit and upgrading GCC">
># emerge -an gentoolkit
># emerge -uav gcc
><comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
>version and CHOST settings you've upgraded to:)</comment>
># gcc-config i686-pc-linux-gnu-3.4.5
># source /etc/profile
>
><comment>(Rebuilding libtool)</comment>
># emerge --oneshot -av libtool
></pre>
>
>
>Now, we want to see which packages that revdep-rebuild will want to rebuild.
>Then we will tell revdep-rebuild to actually rebuild the packages. This may take
>some time, so have some patience.
>
>
><pre caption="Using revdep-rebuild">
># revdep-rebuild --library libstdc++.so.5 -- -p -v
># revdep-rebuild --library libstdc++.so.5
></pre>
>
><note>
>It is possible that you might have problems with non-existing package versions
>due to them being outdated or masked. If this is the case, you will want to use
>the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
>to be recompiled based on the package name, rather than the exact name and
>version.
></note>
>
>
>To provide compatibility with older binary C++ applications and any packages
>that revdep-rebuild might have missed, <c>sys-libs/libstdc++-v3</c> needs to be
>merged before you unmerge GCC 3.3 from your system.
>
>
><pre caption="Installing libstdc++-v3 and cleaning up">
># emerge --oneshot sys-libs/libstdc++-v3
># emerge -aC =sys-devel/gcc-3.3*
></pre>
>
></body>
></section>
><section id="upgrade-3.3-to-3.4-emerge-e">
><title>Using emerge -e</title>
><body>
>
>
>This method, while much slower, will rebuild your whole system to ensure that
>everything has been rebuilt with your new compiler, and therefore safer. At
>first, you will upgrade GCC and libtool and switch to your new compiler.
>
>
><pre caption="Upgrading GCC">
># emerge -uav gcc
><comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
>version and CHOST settings you've upgraded to:)</comment>
># gcc-config i686-pc-linux-gnu-3.4.5
># source /etc/profile
>
><comment>If you upgraded from gcc 3 to 4 (e.g. from 3.3.6 to 4.1.1 in this
>example) you will have to run fix_libtool_files.sh manually</comment>
># fix_libtool_files.sh 3.3.6
>
><comment>(Rebuilding libtool)</comment>
># emerge --oneshot -av libtool
></pre>
>
>
>To provide compatibility with older binary C++ applications,
><c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
>
>
><pre caption="Installing libstdc++-v3">
># emerge --oneshot sys-libs/libstdc++-v3
></pre>
>
>
>Now we will go about first rebuilding the system target, then the world target.
>This will take a very long time, depending on the number of packages that you
>have installed, as it will rebuild your entire toolchain and supporting system
>files, followed by every package on your system, including the toolchain. This
>is necessary to ensure that all packages have been compiled with the new
>toolchain, including the toolchain itself.
>
>
><pre caption="Rebuilding system and world">
># emerge -e system
># emerge -e world
></pre>
>
>
>It is also safe to remove older GCC versions at this time:
>
>
><pre caption="Cleaning up">
># emerge -aC =sys-devel/gcc-3.3*
></pre>
>
></body>
></section>
></chapter>
>
><chapter id="first-install">
><title>Upgrading to GCC on a First Install</title>
><section>
><title>Introduction</title>
><body>
>
>
>A GCC upgrade on a system after installation from a stage3 tarball is a simple
>affair. One advantage users of new installations have is they do not have a
>plethora of software installed that links against the older version of GCC.
>The following example is for a GCC-3.3 to 3.4 or greater upgrade. Certain parts
>will be different if upgrading from other versions of GCC. For example, the
>library names used for <c>revdep-rebuild</c> below are GCC 3.3 specific, as
>well as the need to install <c>libstdc++-v3</c>.
>
>
>
>If a user has not made any customizations to their system yet, then there are
>very few steps to get their system upgraded to a new GCC version. As with the
>GCC-3.3 to 3.4 upgrade, the user has a couple options. However, unlike the
>GCC-3.3 to 3.4 upgrade, this one is less complicated as there are fewer
>differences between the methods. The <uri
>link="#first-install-revdep-rebuild">first method</uri> is faster and makes use
>of the <c>revdep-rebuild</c> tool from <c>gentoolkit</c>, similar to the above
>procedure. Using revdep-rebuild causes only packages which actually link
>against GCC libraries to be rebuilt, while the <uri
>link="#first-install-emerge-e">second method</uri> causes your entire new
>install to be recompiled with the new GCC version and takes much longer. This
>second method is never required and only documented for completeness.
>
>
>
>These first steps are common between both methods, and should be completed by
>everyone.
>
>
><pre caption="Upgrading GCC">
># emerge -uav gcc
><comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
>version and CHOST settings you've upgraded to:)</comment>
># gcc-config i686-pc-linux-gnu-3.4.5
># source /etc/profile
>
><comment>(Rebuilding libtool)</comment>
># emerge --oneshot -av libtool
></pre>
>
>
>To provide compatibility with older binary C++ applications,
><c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
>
>
><pre caption="Installing libstdc++-v3">
># emerge --oneshot sys-libs/libstdc++-v3
></pre>
>
></body>
></section>
>
><section id="first-install-revdep-rebuild">
><title>Using revdep-rebuild</title>
><body>
>
>
>This method requires that you first install <c>gentoolkit</c> if you have not
>already done so. We will then run <c>revdep-rebuild</c> to actually scan the
>installed packages for ones we need to rebuild, then rebuild them.
>
>
><pre caption="Installing gentoolkit and running revdep-rebuild">
># emerge -an gentoolkit
># revdep-rebuild --library libstdc++.so.5 -- -p -v
># revdep-rebuild --library libstdc++.so.5
></pre>
>
><note>
>It is possible that you might have problems with non-existing package versions
>due to them being outdated or masked. If this is the case, you will want to use
>the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
>to be recompiled based on the package name, rather than the exact name and
>version.
></note>
>
></body>
></section>
><section id="first-install-emerge-e">
><title>Using emerge -e</title>
><body>
>
>
>This method, while much slower, will rebuild the system target to ensure that
>everything has been rebuilt with your new compiler. This is not necessary, but
>is valid if you are also making changes to CFLAGS or other make.conf variables
>that will affect the system compile.
>
>
>
>Since we are performing these actions after an initial installation, we do not
>need to recompile the <c>world</c> target as we would when doing an upgrade on
>an already installed system. However, you may choose to perform a world update
>in place of the system update, to ensure that all packages are updated.
>
>
><pre caption="Rebuilding system">
># emerge -e system
></pre>
>
></body>
></section>
><section id="first-install-cleaning-up">
><title>Cleaning up</title>
><body>
>
>
>It is also safe to remove older GCC versions at this time. Please substitute
><c>YOUR-NEW-GCC-VERSION</c> with the actual version you've upgraded to:
>
>
><pre caption="Cleaning up">
># emerge -aC "&lt;sys-devel/gcc-YOUR-NEW-GCC-VERSION"
></pre>
>
></body>
></section>
></chapter>
>
><chapter id="common-pitfalls">
><title>Common Pitfalls</title>
><section>
><body>
>
>
>It's important to disable <c>distcc</c> during upgrade. Mixing compiler versions
>on your nodes <e>will</e> cause build issues. This is not required for ccache,
>as the cache objects will be invalidated anyway.
>
>
>
>Always use same GCC version for your kernel and additional kernel modules. Once
>you rebuild your world with new GCC, external modules (like
><c>app-emulation/qemu-softmmu</c>) will fail to load. Please rebuild your kernel
>with new GCC to fix that.
>
>
>
>If you're upgrading on a SPARC machine, make sure to rerun <c>silo -f</c> after
>re-emerging world to avoid possible issues.
>
>
></body>
></section>
><section>
><title>Frequent Error Messages</title>
><body>
>
>
>If your system complains about something like <e>libtool: link:
>`/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.la' is not a valid libtool
>archive</e>, please run <c>/sbin/fix_libtool_files.sh 3.3.6</c> (substitute
>"3.3.6" with the version numbers from the error message).
>
>
>
>If you see the <e>error: /usr/bin/gcc-config: line 632:
>/etc/env.d/gcc/i686-pc-linux-gnu-3.3.5: No such file or directory</e>, then try
>deleting <path>/etc/env.d/gcc/config-i686-pc-linux-gnu</path> and running
><c>gcc-config</c> again, followed by <c>source /etc/profile</c>. Only do this if
>you do not have any cross-compilers set up, though.
>
>
>
>If a package fails during <c>emerge -e system</c> or <c>emerge -e world</c>,
>you can resume operation with <c>emerge --resume</c>. If a package fails
>repeatedly, skip it with <c>emerge --resume --skipfirst</c>. Don't run any
>other instances of emerge in between or you will lose the resume information.
>
>
>
>If you get an error message <e>spec failure: unrecognized spec option</e> while
>upgrading your compiler, try to switch back to your default compiler, unset the
><c>GCC_SPECS</c> variable and upgrade GCC again:
>
>
><pre caption="Restoring primary specs">
># gcc-config 1
># source /etc/profile
># unset GCC_SPECS
># emerge -uav gcc
></pre>
>
></body>
></section>
></chapter>
></guide>

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