Hello all,
I'm a contributor to the Wine project. To summarize the following mail,
Wine needs special versions of some of its normal dependencies, such as
libfreetype and libgnutls, built using the MinGW cross-compiler, and I'm
sending out a mail to major distributions in order to get some feedback
from our packagers on how these should be built and packaged.
For a long time Wine has built all of its Win32 libraries (DLLs and
EXEs) as ELF binaries. For various reasons related to application
compatibility, we have started building our binaries as PE instead,
using the MinGW cross-compiler. It is our intent to expand this to some
of our dependencies as well. The list of dependencies that we intend to
build using MinGW is not quite fixed yet, but we expect it to include
and be mostly limited to the following:
* libvkd3d
* libFAudio
* libgnutls
* zlib (currently included via manual source import)
* libmpg123
* libgsm
* libpng
* libjpeg-turbo
* libtiff
* libfreetype
* liblcms2
* jxrlib
and dependencies of the above packages (not including CRT dependencies,
which Wine provides).
There is currently some internal discussion about how these dependencies
should be built and linked. There are essentially three questions I see
that need to be resolved, and while these resolutions have a significant
impact on the Wine building and development process, they also have an
impact on distributions, and accordingly I'd like to get input from our
packagers to ensure that their considerations are accurately taken into
account.
(1) Should we build via source import, or link statically, or dynamically?
Static linking and source imports are dispreferred by Fedora [1] [2], as
by many distributions, on the grounds that they cause duplication of
libraries on disk and in memory, and make it harder to update the
libraries in question (see also question 2). They also make building and
bisecting harder.
Note however that if they are linked dynamically, we need to make sure
that we load our packages instead of MinGW builds of open-source
libraries with applications ship with. Accordingly we need each library
to be renamed, and to link to renamed dependencies. For example, if
application X ships with its own copy of libfreetype-6.dll, we need to
make sure that our gdi32.dll links to libwinefreetype-6.dll instead, and
that libwinefreetype-6.dll links to libwineharfbuzz-0.dll and
winezlib.dll. I think, although I haven't completely verified yet, that
this can be done just with build scripts (i.e. no source patches), by
using e.g. --with-zlib=/path/to/winezlib.dll.
Accordingly, although static linking and source imports are generally
disprefered, it may quite likely be preferable in our case. We don't get
the benefits of on-disk deduplication, since Wine is essentially the
only piece of software which needs these libraries.
(2) If we use dynamic libraries, should dependencies be included in the
main wine package, or packaged separately?
This is mostly a question for packagers, although it also relates to (3).
I expect that Fedora (and most distributions) want to answer "packaged
separately" here, on the grounds that this lets them update (say) Wine's
libgnutls separately, and in sync with ELF libgnutls, if some security
fix is needed. There is a snag, though: we need libraries to be copied
into the prefix (there's some internal effort to allow using something
like symlinks instead, but this hard and not done yet). Normally we
perform this copy every time Wine is updated, but if Wine and its
dependencies aren't updated on the same schedule, we may end up loading
an old version of a dependency in the prefix, thus missing the point of
the update.
(3) If dependencies are packaged separately, should Wine build them as
part of its build tree (e.g. using submodules), or find and link
(statically or dynamically) to existing binaries?
Linking to existing binaries is generally preferable: it avoids
duplication on disk; it reduces compile times when compiling a single
package from source (especially the first time). However, we aren't
going to benefit from on-disk duplication. And, most importantly, unlike
with ELF dependencies, there is no standardized way to locate MinGW
libraries—especially if it comes to Wine-specific libraries. We would
need a way for Wine's configure script to find these packages—and
ideally find them automatically, or else fall back to a submodule-based
approach.
If we rely on distributions to provide our dependencies, the best idea I
have here would be something like a x86_64-w64-mingw32-pkg-config. And
if we use shared libraries rather than static, things get worse: we need
to know the exact path of each library and its dependencies so that we
can copy (or symlink) them into a user's WINEPREFIX.
For what it's worth, the current proposed solution (which has the
support of the Wine maintainer) involves source imports and submodules.
There's probably room for changing our approach even after things are
committed, but I'd still like to get early feedback from distributions,
and make sure that their interests are accurately represented, before we
commit. In short, it's not clear whether distributions want their
no-static-library policies to apply to us as well, or whether we're
enough of a special case and would be enough of a pain to package that
they'd rather we deal with the hard parts, and I don't want us to make
any assumptions.
ἔρρωσθε,
Zebediah
[1]
https://docs.fedoraproject.org/en-US/packaging-guidelines/#packaging-static-libraries
[2] https://fedoraproject.org/wiki/Bundled_Libraries
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