Re: Optional libraries

[Eli Zaretskii <eliz@gnu.org>]

> From: Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>
> Date: Mon, 19 Sep 2016 02:05:20 +0300
> 
> I'm currently trying to make sense of the possible optional libraries that are used on Windows.

Dependency Walker (http://www.dependencywalker.com/) is your friend.
You can run it for each DLL and see its dependency DLLs.

> Can someone help me document them?
> 
> Here's a list I lifted from emacs-w64 project, with some commentaries added.

I try adding some info below, but I don't have MinGW64 and cannot
check things myself.  (I also find many MSYS2 packages bloated with
unneeded stuff, which then requires users to have many redundant DLLs
around.)

> libbwinpthread-*.dll ; msys2 built emacs does not work without it? Does not exist in official builds...

I believe the MinGW64 GCC produces DLLs that depend on this and on
libgcc_s_seh-*.dll.  The package builders should be told to avoid
that, since these 2 dependencies require the corresponding sources be
available (and the sources for libgcc_s_seh-*.dll is the entire 80MB
GCC distribution).

> libdbus-*.dll ; is there a single legitimate usecase for dbus on windows?

There could be, but Emacs built for Windows doesn't support D-Bus, so
until that support is added, linking with this DLL is futile.

> ;; Image support
> libpng*.dll ; png images
> libtiff-*.dll
> libtiffxx-*.dll ; tiff images

The last one is for C++ programs, so not needed for Emacs.

> libjpeg-*.dll ; jpeg images
> libgif-*.dll ; gif images
> libXpm-noX*.dll ; xpm images
> ;; rsvg dependencies
> libglib-*.dll
> libcairo-*.dll
> libcroco-*.dll
> libpango-*.dll
> libpangocairo-*.dll
> libpangoft*.dll
> libpangowin32-*.dll
> librsvg-*.dll ; svg images

You've missed some rsvg dependencies, which appear under "unknown":

> libgobject-*.dll
> libgdk_pixbuf-*.dll
> libgio-*.dll
> libgmodule-*.dll
> libfontconfig-*.dll
> libfreetype-*.dll
> libpixman-*.dll
> libharfbuzz-*.dll

> ;; Gnutls dependencies
> libffi-*.dll ; only needed for msys2-based builds
> libgmp-*.dll
> libgnutls-*.dll
> libgnutls-openssl-*.dll ; only in Eli's gnutls build

It's in the GnuTLS binary distro, but is not needed for Emacs.

> libgnutlsxx-*.dll ; only in msys2, same library as the previous one, with a different name?

No, it's C++ APIs for GnuTLS; again, not needed for Emacs.

> libhogweed-*.dll
> libiconv-*.dll
> libidn-*.dll ; only needed for msys2-based builds
> libintl-*.dll
> libnettle-*.dll
> libp11-kit-*.dll
> libtasn1-*.dll
> zlib*.dll

zlib is also used by Emacs directly.

> ;; Unknown
> libgomp-*.dll

This one is part of GCC, use the Dependency Walker to see who needs
it, if at all.

> libxml2-*.dll

This is the XML support library, required for HTML and XML support in
Emacs.

> libexpat-*.dll

Not sure which DLL needs it, perhaps libxml2?

> liblzma-*.dll
> libbz2-*.dll
> libjbig-*.dll

Perhaps rsvg dependencies?

HTH