Latest revision as of 14:41, 15 October 2011

Mono Default Paths / Multiarch Changes

Summary

Change the default path for mono assemblies (and mono's global assembly cache) from %{_libdir} to /usr/lib. This will remove the multiarch support for mono on x86-64 systems.

Owner

Name: Christian Krause

Email: chkr@fedoraproject.org

Current status

Targeted release: Fedora 17
Last updated: (DATE)
Percentage of completion: 00%

Detailed Description

The way how mono is packaged in Fedora is uncommon with respect to mono's default search path. For various reasons the default path for mono assembles and the mono "Global Assembly Cache" ( /usr/lib and /usr/lib/mono) was changed to %{_libdir} in Fedora. This causes lots of unnecessary work by the maintainers and quite a couple of bug reports due to uncaught uses of these default paths within the mono packages. Reverting this decision and using again mono's standard search path /usr/lib would result in conflicts between i686 and x86_64 packages because both would contain the same files. Although the assemblies are the same, the files may differ due to strings referring to the build architecture).

That means, that we would have to prevent that any mono i686 package would be drawn into the x86_64 repos and so we would loose the ability to use 32bit parts of the mono stack in x86-64 - a feature which never worked correctly and is not available for other run-time environments like perl or python either.

Benefit to Fedora

Much easier maintenance of all mono-based packages since all patches and hacks to change /usr/lib to %{_libdir} are not necessary anymore.

Scope

the Fedora-specific %{_libdir} patches have to be removed from all mono-based packages and they have to be re-compiled
repoquery reports 114 packages which may be 50 separate source packages
rel-eng must change the mash scripts to prevent that any 32-bit mono-based packages are drawn into the x86_64 repository

How To Test

install any mono-based package you like to use (preferably on x86 and on x86-64 systems)
try whether it still works correctly

User Experience

Most user won't recognize it.
It may solve some unreported issues caused by the change default paths.
There may be some users who used the 32-bit mono core packages in x86-64. These packages will not be available anymore.

Dependencies

the "mash" tool to generate the x86-64 repositories must blacklist all -devel RPMS of the mono-based packages

Contingency Plan

do the recompilation of all packages using a special build-target to check whether it works correctly
in case it turns out that the migration can't be done, the git commits of the modified mono-based packages must be reverted
since no builds were done for dist-rawhide, no rebuilds are necessary in that case

Documentation

Rationale

mono-based packages may contain mono assemblies (arch-independent) and ELF binaries (e.g. glue code etc., arch-dependent)
the assemblies are usually put in the GAC, mono's "global assembly cache"
the arch-dependent files are correctly copied into %{_libdir}
upstream places the gac into /usr/lib (/usr/lib/mono/gac) (regardless of the actual architecture)
Fedora moves the GAC into %{_libdir} (which is /usr/lib64 on x86_64) which causes the following issues
- packaging problems - most mono packages have this path hard-coded or even generate the path names at run-time, so all mono packages must be patched
- Fedora encourages the packagers to stay close to upstream and provide all changes as patches to upstream, however since in this case Fedora diverges from upstream (and all other distributions), none of the necessary patches and fixes for changing /usr/lib to /usr/lib64 can be upstreamed
- Upstream does not care about any issues Fedora has regarding any problems which result of using %{_libdir}
- Fixing all of the issues is a tedious and self-defeating work which actually does not solve any real-world problems but is only necessary because of Fedora's "self-made" problem

There are two main questions:

Are mono assemblies (*.dll, *.exe) architecture independent?
Fedora previously assumed, that they are not (based on http://lists.alioth.debian.org/pipermail/pkg-mono-devel/2005-February/000370.html )
- I have verified with mono upstream, that this is not their position anymore:
  - mono assemblies are in general architecture independent, every CLI runtime-environment should be able to execute them
  - in theory it is possible to write architecture-dependent native bindings, but doing so is discouraged and is treated (even by upstream) as a bug which should be fixed
  - if it is hard to generate a binding because of platform dependencies in the native library, the developers are encouraged to write gluecode libraries (native) which provide an interface which C# code can utilize with platform independent code
  - details: http://lists.ximian.com/pipermail/mono-devel-list/2011-May/037591.html , http://lists.ximian.com/pipermail/mono-devel-list/2011-May/037593.html
  - AOT compilations would be architecture-dependent, but they are not in use right now

Given that mono assemblies are platform independent, should they go into %{_datadir} or /usr/lib ?
- FHS specifies, that libraries should go to /usr/lib ( http://www.pathname.com/fhs/pub/fhs-2.3.html#USRLIBLIBRARIESFORPROGRAMMINGANDPA )
- FHS specifies further: "The /usr/share hierarchy is for all read-only architecture independent data files [...] Much of this data originally lived in /usr (man, doc) or /usr/lib (dict, terminfo, zoneinfo)."
- FHS does not forbid to place arch-independent files into /usr/lib. It only forbids to place arch-dependent files into /usr/share
- Placing the mono assemblies into /usr/share would not solve the mentioned issue (see above)

What does other distributions do:
- Fedora is the only distribution which has made these changes
  - OpenSUSE
    - packages only containing mono bytecode are noarch
    - GAC still in /usr/lib
    - example: https://build.opensuse.org/package/binary?arch=x86_64&filename=gtk-sharp2-2.12.10-23.2.x86_64.rpm&package=gtk-sharp2&project=openSUSE%3A11.3&repository=standard
  - Debian
    - custom location for the GAC in newer releases (but still in /usr/lib)
    - example: http://packages.debian.org/sid/amd64/libgtk2.0-cil/filelist

Examples for the currently necessary patches

example from monodevelop.spec:


sed -i -e 's!$(prefix)/lib/!%{_libdir}/!' \
    -e 's!${exec_prefix}/lib!%{_libdir}!' configure
sed -i -e 's!/lib/monodevelop!/%{_lib}/monodevelop!' monodevelop
sed -i -e 's!$PREFIX/lib/!%{_libdir}/!' mdtool.in
sed -i -e 's!monodevelop}/lib/!monodevelop}/%{_lib}/!' monodevelop.in

find . -name '*.cs' -and \
     ! \( -name 'GNUCompiler.cs' -or -name 'CProjectConfiguration.cs' \) \
      | while read f ;
        do
        sed -i -e 's!"lib"!"%{_lib}"!' "$f" 1>/dev/null
        done

find . -name Makefile.in -or -name \*.pc.in \
       -or -name \*.in -or -name \*.xml \
       | while read f ;
         do
           sed -i -e 's!$(prefix)/lib/!%{_libdir}/!' \
               -e 's!@prefix@/lib/!%{_libdir}/!' \
               -e 's!/usr/lib/!%{_libdir}/!' \
               -e 's!${exec_prefix}/lib/!%{_libdir}/!' "$f" 1>/dev/null
         done

another example from mono-basic.spec

%prep
%setup -q
sed -i -e 's!@libdir@!%{_libdir}!' %{PATCH0}
%patch0 -p1 -b .original
sed -i -e 's!%{_libdir}!@libdir@!' %{PATCH0}
sed -i -e 's!$(prefix)/lib/!%{_libdir}/!' build/config-default.make
sed -i -e 's!${exec_prefix}/lib!%{_libdir}!' configure

Necessary Changes

general rule: remove all patches and "sed" calls in the spec file of the mono-based packages which deals with altering the lib path
- ensure, that mono assemblies (for both i686 and x86_64 packages!) are either
  - correctly installed into the gac in /usr/lib/mono or
  - installed into /usr/lib/$monoprogram
- ensure, that ELF binaries are correctly installed into %{_libdir}
blacklist all mono packages from mash's "multi-arch" selection rule which pulls in 32bit packages into x86-64
these rules follow the same ideas as used by the python packages (in Fedora) and the mono packages in OpenSUSE
like OpenSUSE we may also change all mono packages which only contain mono binaries and no ELF binaries to noarch
packages which contain mono assemblies and ELF libraries should not be splitted but they will remain arch-dependent:
- does not solve any real issues
- unnecessary work
- not done for perl and python either

detailed step-by-step
1. announce changes on fedora-mono mailing list
2. ask rel-eng for a special koji-target: "f17-mono" to update the 64 packages without interfering with rawhide
3. fix/verify mono core packages: mono, libgdiplus, mono-tools, boo, nant, mono-addins, gtk-sharp in rawhide
4. fix all remaining mono-based packages:

avahi-0:0.6.30-4.fc17.src
banshee-0:2.0.1-2.fc16.src
banshee-community-extensions-0:2.0.1-2.fc16.src
bareftp-0:0.3.9-1.fc17.src
blam-0:1.8.7-3.fc14.src
bless-0:0.6.0-7.fc16.src
boo-0:0.9.4.9-2.fc16.src
cdcollect-0:0.6.0-12.fc15.src
chronojump-0:0.8.14-1.fc12.src
clutter-sharp-0:0-0.14.20090828.fc17.src
dbus-sharp-0:0.63-17.fc15.src
docky-0:2.0.12-1.fc17.src
f-spot-0:0.8.2-3.fc16.src
flickrnet-0:2.2-8.fc15.src
gdata-sharp-0:1.4.0.2-5.fc15.src
gecko-sharp2-0:0.13-20.fc16.src
gio-sharp-0:0.3-2.fc16.src
gkeyfile-sharp-0:0.1-7.fc16.src
gmime-0:2.5.8-1.fc16.src
gnome-desktop-sharp-0:2.26.0-13.fc15.src
gnome-do-0:0.8.5-7.fc17.src
gnome-do-docklets-0:0.8.2-4.fc15.src
gnome-do-plugins-0:0.8.4-2.fc16.src
gnome-guitar-0:0.8.1-10.fc16.src
gnome-keyring-sharp-0:1.0.1-0.8.133722svn.fc15.src
gnome-rdp-0:0.2.3-9.fc16.src
gnome-sharp-0:2.24.1-6.fc16.src
gnome-subtitles-0:1.2-1.fc17.src
gsf-sharp-0:0.8.1-15.fc15.src
gtk-sharp2-0:2.12.11-1.fc17.src
gtksourceview-sharp-0:2.0.12-14.fc16.src
gtksourceview2-sharp-0:1.0-10.svn89788.fc16.src
ice-0:3.4.2-3.fc17.src
libgpod-0:0.8.2-1.fc16.src
log4net-0:1.2.10-16.fc16.src
mod_mono-0:2.10-1.fc16.src
mono-addins-0:0.6.2-2.fc17.src
mono-basic-0:2.10-2.fc17.src
mono-bouncycastle-0:1.7-1.fc16.src
mono-cecil-flowanalysis-0:0.1-0.15.20110512svn100264.fc16.src
mono-debugger-0:2.10-1.fc16.src
mono-nat-0:1.1.0-1.fc16.src
mono-reflection-0:0.1-0.2.20110613git304d1d.fc16.src
mono-tools-0:2.10-3.fc16.src
mono-zeroconf-0:0.9.0-5.fc15.src
monodevelop-0:2.6-2.fc17.src
monodevelop-debugger-gdb-0:2.6-1.fc17.src
monodevelop-vala-0:2.6-1.fc17.src
monsoon-0:0.21-4.fc13.src
nant-1:0.90-6.fc16.src
ndesk-dbus-0:0.6.1b-1.fc13.src
ndesk-dbus-glib-0:0.4.1-10.fc15.src
notify-sharp-0:0.4.0-0.14.20100411svn.fc15.src
pinta-0:1.0-1.fc16.src
taglib-sharp-0:2.0.3.7-3.fc16.src
taoframework-0:2.1.0-3.fc17.src
themonospot-base-0:0.8.2-7.fc16.src
themonospot-console-0:0.1.1-6.fc16.src
themonospot-gui-gtk-0:0.2.2-7.fc16.src
themonospot-gui-qt-0:0.1.3-10.fc16.src
themonospot-plugin-avi-0:0.1.1-6.fc16.src
themonospot-plugin-mkv-0:0.1.1-6.fc16.src
webkit-sharp-0:0.3-6.fc16.src
xsp-0:2.10.2-1.fc16.src

- if everything works as expected, ask rel-eng to block the mono-devel packages from mash'ing into multi-arch x86_64

Release Notes

no specific release notes necessary

Comments and Discussion

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