[arch-general] Wine MinGW system libraries

[Zebediah Figura]

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?

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. There's some internal discussion 
about whether this is possible while using "stock" builds of MinGW 
libraries, but, due to the way the Win32 loader works, we may need to 
compile each library, and its dependencies, with a separate, 
wine-specific name, e.g. "libwinefreetype-6.dll" and 
"libwineharfbuzz.dll". For a detailed explantion see footnote [3]. Note 
that all we actually need to change is the name; we don't need to patch 
the source.

(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).

(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. There is a 
MinGW version of pkg-config shipped by many distributions, which lets us 
find libraries, but there's no standardized way to find them at runtime. 
(Arch does not ship this, although it's available in the AUR [2].)

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.

ἔρρωσθε,
Zebediah


[1] The basic problem is that applications can and often do ship with PE 
builds of cross-platform libraries. These libraries can be ahead of 
Wine's system libraries, behind them, or even built with custom patches. 
Accordingly we really don't want to load "our" freetype in place of 
"their" freetype, or "theirs" in place of "ours". But because of the way 
the Win32 loader works, you can generally only have one DLL of a given 
name loaded in a process, and further attempts to dlopen() [as it were] 
"libfreetype-6.dll" will return the handle to the already loaded 
library, potentially breaking either Wine or the application. There 
*may* be ways we can hack around this internally, but it's not clear 
that it's feasible yet, and so it's probably best to assume that we'll 
need special builds of dynamic libraries.

[2] https://aur.archlinux.org/packages/mingw-w64-pkg-config/