OutOfTreeCompile

This page outlines setting up a module for building outside of the main VLC source tree. See also how to write a module.

Source code

There are a few differences that need to be taken into account when writing a module out-of-tree:

• MODULE_STRING must be defined manually (in-tree, the VLC build system takes care of it).
• The static import compatibility library (compat/libcompat.la) is not available. If a function is missing on the target platform, you will need to work around it yourself.
• <config.h> is not available either, so none of the HAVE_* and CAN_* macros are defined out-of-the-box. You will need to ensure that your build system provides any such macro that the module source code depends on.
• Similarly, the gettext functional macros N_(), _(), vlc_pgettext() and gettext_noop() are not defined automatically.
• Some (few) parts of the VLC core API are unavailable. Their header files are provided externally.

Internationalization

The VLC build system cannot scan out-of-tree source code for text to be translated. If you want gettext translations, you need to setup gettext in the build system and maintain the PO files.

However, the VLC core is able to load your module text domain into the process automatically. This is required for the plugins cache to operate correctly. You simply need to add one "set_text_domain" line in the module descriptor, e.g.:

#define DOMAIN  "vlc-myplugin"
#define _(str)  dgettext(DOMAIN, str)
#define N_(str) (str)

/* ... */

vlc_module_begin()
   set_text_domain (DOMAIN)
   set_description (N_("My plugin"))
   /* ... */
vlc_module_end()

You might find it hard to maintain this, and ignore internationalization altogether.

Symbols

External VLC modules are run-time libraries. They need to expose some predefined symbols (functions). They all start with the prefix "vlc_entry_". In principles, the vlc_module_begin() macro ensures that those function are exported, so you should not worry about this.

Installing the development files

The VLC header files, the pkg-config files, and import libraries are required.

On Debian/Ubuntu, you can simply install them:

% sudo apt-get install libvlc-dev

On Windows, you can find those files within the vlc-*-win*.zip file, inside the sdk/ directory.

Building

Note that the following examples assume that the VLC development package is installed and configured correctly. In particular, these commands should work (results may vary though):

% pkg-config --modversion vlc-plugin
1.1.13

% pkg-config --cflags vlc-plugin
-D__PLUGIN__ -D_FILE_OFFSET_BITS=64 -D__USE_UNIX98 -D_REENTRANT -D_THREAD_SAFE -I/usr/include/vlc/plugins  

% pkg-config --libs vlc-plugin
-lvlccore  

If cross-compiling, you will probably need to adjust the pkg-config environment variables.

Makefile

This is an example plain makefile (using GNU/make syntax) for Linux/BSD/Solaris:

PREFIX = /usr
LD = ld
CC = cc
INSTALL = install
CFLAGS = -g -O2 -Wall -Wextra
LDFLAGS =
VLC_PLUGIN_CFLAGS := $(shell pkg-config --cflags vlc-plugin)
VLC_PLUGIN_LIBS := $(shell pkg-config --libs vlc-plugin)

libdir = $(PREFIX)/lib
plugindir = $(libdir)/vlc/plugins

override CC += -std=gnu99
override CPPFLAGS += -DPIC -I. -Isrc
override CFLAGS += -fPIC
override LDFLAGS += -Wl,-no-undefined,-z,defs

override CPPFLAGS += -DMODULE_STRING=\"foo\"
override CFLAGS += $(VLC_PLUGIN_CFLAGS)
override LDFLAGS += $(VLC_PLUGIN_LIBS)

TARGETS = libfoo_plugin.so

all: libfoo_plugin.so

install: all
        mkdir -p -- $(DESTDIR)$(plugindir)/misc
        $(INSTALL) --mode 0755 libfoo_plugin.so $(DESTDIR)$(plugindir)/misc

install-strip:
        $(MAKE) install INSTALL="$(INSTALL) -s"

uninstall:
        rm -f $(plugindir)/misc/libfoo_plugin.so

clean:
        rm -f -- libfoo_plugin.so src/*.o

mostlyclean: clean

SOURCES = foo.c bar.c

$(SOURCES:%.c=src/%.o): %: src/foo.h

libfoo_plugin.so: $(SOURCES:%.c=src/%.o)
        $(CC) $(LDFLAGS) -shared -o $@ $^

.PHONY: all install install-strip uninstall clean mostlyclean

with GNU/autotools

If using automake and libtool, you can follow this instead:

configure.ac

# ...

AC_PROG_CC_C99
AM_PROG_CC_C_O
AM_PROG_LIBTOOL
PKG_PROG_PKG_CONFIG()

# ...

PKG_CHECK_MODULES(VLC_PLUGIN, [vlc-plugin >= 1.1.0])

Makefile.am

vlclibdir = $(libdir)/vlc

vlclib_libfoo_plugin_la_SOURCES = src/foo.c src/foo.h src/bar.c
vlclib_libfoo_plugin_la_CFLAGS = $(VLC_PLUGIN_CFLAGS) \
      -DMODULE_STRING=\"foo\"
vlclib_libfoo_plugin_la_LIBADD = $(VLC_PLUGIN_LIBS)
vlclib_libfoo_plugin_la_LDFLAGS = \
      -avoid-version -module -export-symbol-regex ^vlc_entry