When I use a function wich have as C argument:

const gchar**

So in vala code I call this function like this:

func({ "some string" });

But this code cause a gcc & Clang/LLVM warning (for Gtk.AboutDialog.set_authors):

src/about.c:89:56: warning: passing 'gchar **' (aka 'char **') to parameter of
      type 'const gchar **' (aka 'const char **') discards qualifiers in nested
      pointer types
        gtk_about_dialog_set_authors ((GtkAboutDialog*) self, _tmp5_);
                                                              ^~~~~~
In file included from src/about.c:7:
In file included from /usr/include/gtk-2.0/gtk/gtk.h:33:
/usr/include/gtk-2.0/gtk/gtkaboutdialog.h:112:26: note: passing argument to
      parameter 'authors' here
  ...const gchar    **authors);

In C code, a new temporary variable is created, but it's useless !

I tested two ways to fix this:

1) A local constant array
2) A class/global constant array

The fist way produce a gcc & Clang/LLVM error:

src/about.c:63:28: error: initializer element is not a compile-time constant
        static const gchar* a[] = {_tmp0_};

The second way works but it's not optimised ! (use a C static variable)

Note: I use Clang/LLVM for warnings and errors because it's more detailed.