A simple test to show the memory leak from the Vala Compiler called via libvala

libvalaleak.vala

public static void parse (string[] args) {
	Vala.Parser parser = new Vala.Parser ();
	Vala.CodeContext context = new Vala.CodeContext();
	parser.parse (context);
	Vala.CodeContext.push(context);

	foreach (var path in args)
		if (path.has_suffix (".vala") || path.has_suffix (".vapi") || path.has_suffix (".gs"))
			context.add_source_file (new Vala.SourceFile (context, Vala.SourceFileType.SOURCE, path));

	context.add_external_package("glib-2.0");
	context.add_external_package("gobject-2.0");
	context.add_external_package("libvala-0.30");

	foreach (var src in context.get_source_files ())
		parser.visit_source_file (src);

	context.check ();
	Vala.CodeContext.pop();

}

/* the arguments are an array of full paths to valid Vala files */
public static int main (string[] args) {

	int i = 0;
	while (i < 20) {
		// simulate calling the compiler multiple times
		parse(args);
		i++;
	}
	return 0;
}

to compile - valac libvalaleak.vala --pkg libvala-0.XX to run simply pass the full path of any number of vala files

Interesting results...
vala_code_visitor_ref//unref 80/100
vala_code_context_ref/unref 31920/31880