Plugin Sample (GModule)

This sample loads a shared library at runtime with GLib.Module and calls an exported C symbol from Vala. It is a minimal GModule example (no TypeModule registration).

Plugin (plugin.vala)

The plugin exposes a plain entry function. Build it as a shared library (see below).

// plugin.vala
public void plugin_entry () {
    print ("Hello from the plugin.\n");
}

Loader (loader.vala)

// loader.vala
[CCode (has_target = false)]
private delegate void PluginEntryFunc ();

int main () {
    string path = Module.build_path (Environment.get_current_dir (), "plugin");
    unowned Module? m = Module.open (path, ModuleFlags.BIND_LAZY);
    if (m == null) {
        error ("Could not open module: %s", Module.error ());
    }

    void * sym;
    if (! m.symbol ("plugin_entry", out sym)) {
        error ("Could not find plugin_entry: %s", Module.error ());
    }

    ((PluginEntryFunc) sym) ();
    return 0;
}

Module.build_path picks a filename appropriate for the platform (for example libplugin.so on GNU/Linux).

Build

Generate C from the plugin, then link a shared library:

valac -C plugin.vala
gcc -fPIC -shared -o libplugin.so plugin.c $(pkg-config --cflags --libs glib-2.0 gobject-2.0 gmodule-2.0)
valac -o loader loader.vala --pkg=gmodule-2.0

Run

Point the dynamic loader at the directory that contains libplugin.so:

LD_LIBRARY_PATH=$PWD ./loader

On macOS, use DYLD_LIBRARY_PATH instead of LD_LIBRARY_PATH if you build a .dylib.

For a type-aware plugin that registers GObject types from a module, see TypeModule sample and the Type Modules developer guide.