(gdb) bt full
#0  0x00007ffff4cd74ed in getenv () at /usr/lib/libc.so.6
#1  0x00007ffff717728d in ArdourCanvas::Canvas::render(ArdourCanvas::Rect const&, Cairo::RefPtr<Cairo::Context> const&) const () at /usr/lib/ardour6/libcanvas.so.0
#2  0x00007ffff7177611 in ArdourCanvas::GtkCanvas::on_expose_event(_GdkEventExpose*) () at /usr/lib/ardour6/libcanvas.so.0
#3  0x00007ffff5fb1098 in Gtk::Widget_Class::expose_event_callback(_GtkWidget*, _GdkEventExpose*) () at /usr/lib/libgtkmm-2.4.so.1
#4  0x00007ffff680803c in  () at /usr/lib/libgtk-x11-2.0.so.0
#5  0x00007ffff6c71052 in g_closure_invoke () at /usr/lib/libgobject-2.0.so.0
#6  0x00007ffff6c993d0 in  () at /usr/lib/libgobject-2.0.so.0
#7  0x00007ffff6c8cbab in g_signal_emit_valist () at /usr/lib/libgobject-2.0.so.0
#8  0x00007ffff6c8dae0 in g_signal_emit () at /usr/lib/libgobject-2.0.so.0
#9  0x00007ffff69246f8 in  () at /usr/lib/libgtk-x11-2.0.so.0
#10 0x00007ffff6806e11 in gtk_main_do_event () at /usr/lib/libgtk-x11-2.0.so.0
#11 0x00007ffff6661a90 in  () at /usr/lib/libgdk-x11-2.0.so.0
#12 0x00007ffff6661a33 in  () at /usr/lib/libgdk-x11-2.0.so.0
#13 0x00007ffff6661a33 in  () at /usr/lib/libgdk-x11-2.0.so.0
#14 0x00007ffff6661a33 in  () at /usr/lib/libgdk-x11-2.0.so.0
#15 0x00007ffff665e4cf in  () at /usr/lib/libgdk-x11-2.0.so.0
#16 0x00007ffff665ee20 in gdk_window_process_all_updates () at /usr/lib/libgdk-x11-2.0.so.0
#17 0x00007ffff665ee79 in  () at /usr/lib/libgdk-x11-2.0.so.0
#18 0x00007ffff663d257 in  () at /usr/lib/libgdk-x11-2.0.so.0
#19 0x00007ffff6b80b00 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#20 0x00007ffff6bd21f9 in  () at /usr/lib/libglib-2.0.so.0
#21 0x00007ffff6b80163 in g_main_loop_run () at /usr/lib/libglib-2.0.so.0
#22 0x00007ffff6805b7e in gtk_main () at /usr/lib/libgtk-x11-2.0.so.0
#23 0x00007ffff6ff5ff9 in Gtkmm2ext::UI::run(Receiver&) () at /usr/lib/ardour6/libgtkmm2ext.so.0
#24 0x00005555559f8286 in main ()