Multiarch

What is Multiarch?

In order to ease cross-compiling and distribution, the Debian-based distros have undertaken a project known as "multi-arch." The idea is to update the packaged software itself, and occasionally change how it's built, so that every package can satisfy multiple architectures. Either one version of the package will work for all architectures, or the different architectures' versions can be installed alongside each other.

To be fully compliant, a package not only needs to play well with different architectures, but explicitly state how it operates in a multi-arch environment. This is implemented through values in the control file of each source package, which are then enforced by the distro's package management.

While there are general guidelines, each package has its own dynamic so making it multi-arch compatible is largely up to that package's maintainer. As a result, multi-arch is still a work in progress, and the distros prioritize which packages they focus on.

According to documents from ca. 2013, multi-arch behavior for header-files (common in -dev packages) was undefined. Since then, the Debian-family distros have settled on using subdirectories for multi-arch triplets within /usr/include/. Note that this extension is not yet part of the Filesystem Hierarchy Standard.

Status of Wine Build Dependencies

Perhaps the main (but not only) way this matters to Wine is in regards to building and porting. Once all of Wine's build dependencies are multi-arch compatible, cross-compiling and packaging Wine for different architectures becomes much simpler.

As of August 2017, building Wine 2.14 on Debian Stretch shows the following build dependencies still conflicting across architectures (version info may be different for Ubuntu, Mint, etc.)

Several of these packages will be fixed in Debian Buster, or only conflict because of dependencies that will be. When Debian Buster is released, we can remove them from the table.

Debian Package	Stable Version	Unstable Version	Apt-get Result	Debian Bug Report	Patch Proposed?	Fixed in Stretch?	Fixed in Buster?	Notes
libxml-simple-perl	2.22-1	2.24-1	Package couldn't be found	#869758	✔		✔	Outdated, only used once in dlls/opengl32/make_opengl; consider move to libxml-libxml-simple-perl... or rewrite make_opengl for new tools
oss4-dev	4.2-build2010-2	4.2-build2010-5	Package couldn't be found					Necessary for OSS sound-driver support in Wine. Replaced by ALSA.
khronos-api	0~svn29735-1.1	0~svn33340-0.1	Package couldn't be found	#865308	✔		✔	Supersedes parts of dlls/opengl32/make_opengl
libpcap-dev	1.8.1-3	1.8.1-3	Package couldn't be found	#760370	✔			Transitional package; pulls in libpcap0.8-dev (not yet multi-arch)
gir1.2-gstreamer-1.0	1.4.4-2	1.6.3-1	Satisfies dependencies, but won't be installed					Needed by libgstreamer1.0-dev; see #755874 about multiarch in gobject-introspection
libatk1.0-dev	2.22.0-1	2.24.0-1	Other arch will be removed	#689124	✔		✔	Also depends on libglib2.0-dev
libcairo2-dev	1.14.0-2.1	1.14.6-1	Other arch will be removed	#689122	✔			Also has deps on libfontconfig1-dev, libfreetype6-dev and libglib2.0-dev
libfreetype6-dev	2.6.3-3.2	2.8-0.2	Other arch will be removed	#642354 #870618
libfontconfig1-dev	2.11.0-6.3	2.11.0-6.3	Other arch will be removed	#677885	✔	Partially		Marked as Multi-Arch: same; conflict due to dep on libfreetype6-dev
libgdk-pixbuf2.0-dev	2.31.1-2+deb8u4	2.32.3-1.2	Other arch will be removed	#689125				Reply to report implies gobject-introspection had priority... but see report #755874 for recent resolution
libgirepository1.0-dev	1.42.0-2.2	1.46.0-4	Other arch will be removed	#801672				Again, see #755874; also needs multiarch in gobject-introspection
libglib2.0-dev	2.50.3-2	2.53.4-3	Other arch will be removed	#683593	✔		✔	Also see merged bug report #648621
libgnutls28-dev	3.3.8-6+deb8u3	3.4.9-2	Other arch will be removed	#776841	✔	✔		Package is already marked as Multi-Arch: same; requires nettle-dev to resolve
libgstreamer1.0-dev	1.4.4-2	1.6.3-1	Other arch will be removed					Will also need multiarch in gir1.2-gstreamer-1.0 to resolve conflict
libgstreamer-plugins-base1.0-dev	1.12.2-1	1.12.2-1	Other arch will be removed					Will also need multiarch in libgstreamer1.0-dev, libxml2-dev and gir1.2-gst-plugins-base-1.0 to resolve the conflict.
libgtk2.0-dev	2.24.25-3	2.24.29-1	Other arch will be removed	#689097	Partially			Several dependencies need multiarch to resolve the conflict
libpango1.0-dev	1.36.8-3	1.38.1-1	Other arch will be removed	#683592				See report #763851 for blocking files
libpulse-dev	10.0-1+deb9u1	10.0-2	Other arch will be removed	N/A	N/A	Partially	✔	Already marked Multi-Arch: same; needs multiarch in libglib2.0-dev to resolve
libxft-dev	2.3.2-1	2.3.2-1	Other arch will be removed					Will also need multiarch in libfreetype6-dev to resolve
libxml-parser-perl	2.44-2	2.44-2	Requires dependencies					Requires perl and perl-base to resolve.
libxml2-dev	2.9.4+dfsg1-2.2	2.9.4+dfsg1-3	Other arch will be removed					Requires libicu-dev to resolve.
libxslt1-dev	1.1.29-2.1	1.1.29-2.1	Other arch will be removed					Already marked Multi-Arch: same; requires libxml2-dev to resolve.
nettle-dev	2.7.1-5	3.2-1	Other arch will be removed	#856160		Partially	Partially	Conflicts in /usr/include/nettle/version.h.
unixodbc-dev	2.3.1-3	2.3.1-4	Other arch will be removed

I determined these packages by simulating apt-get build-dep with i386 build-dependencies for the (Debian unstable) version of wine-development:

apt-get -s build-dep wine-development/unstable -a i386

At first, this would return an error for some package; to bypass the error, I used apt-get source to grab the package source, quickly entered a "Multi-Arch: foreign" key into the control file, then rebuilt and installed it. After repeating this for a few packages, the simulated apt-get completed. I didn't need these packages to actually work, only to install and allow apt-get to give a full build-dep list.

See Also

Some of these pages might be out of date, but they're still good places to start:

• The MultiarchSpec on the Ubuntu Wiki
• Multiarch on the Debian Wiki
• MultiarchCross on the Ubuntu Wiki has details about how multi-arch works with -dev packages.