fix register_error_handlers NULL deref in pure Wayland build: move vtable entry out of USE_XWAYLAND guard, add empty stub

src/backend/wayland/wl_backend.c

@@ -920,6 +920,7 @@ wl_display_open(const char *name)
 
     wl_state.pointer_x = 960;
     wl_state.pointer_y = 540;
+    fprintf(stderr, "TRACE: wl_display_open done, returning NULL\n");
     wwarning("wl_backend: virtual pointer initialised at %d,%d",
              wl_state.pointer_x, wl_state.pointer_y);
 
@@ -1838,6 +1839,7 @@ void wl_screen_alloc_gcs(WScreen *scr) { (void)scr; }
       void
 wl_screen_create_internals(WScreen *scr)
 {
+    fprintf(stderr, "TRACE: wl_screen_create_internals\n");
     wl_state.scr = scr;
     {
         FILE *fp = fopen("/tmp/wl_backend_trace.log", "a");

src/backend/wayland/wl_screen.c

@@ -16,6 +16,7 @@
 void
 wl_screen_open(WScreen *scr)
 {
+    fprintf(stderr, "TRACE: wl_screen_open\n");
     /* Set geometry from the headless output created in display_open(). */
     scr->scr_width  = wl_state.output ?
         (int)wl_state.output->width  : 1920;
@@ -45,6 +46,7 @@ void wl_screen_close(WScreen *scr) { (void)scr; }
 int
 wl_screen_init_display(WScreen *scr, int screen_number)
 {
+    fprintf(stderr, "TRACE: wl_screen_init_display\n");
     (void)screen_number;
     scr->w_depth = 32;
     scr->rcontext = RCreateContextWayland(scr->scr_width, scr->scr_height, NULL);
@@ -68,7 +70,7 @@ wl_screen_init_display(WScreen *scr, int screen_number)
     scr->white_pixel = scr->white ? WMColorPixel(scr->white) : 0xFFFFFFFF;
     scr->light_pixel = scr->gray ? WMColorPixel(scr->gray) : 0xFFAAAAAA;
     scr->dark_pixel  = scr->darkGray ? WMColorPixel(scr->darkGray) : 0xFF555555;
-
+    fprintf(stderr, "TRACE: wl_screen_init_display done\n");
     return 1;
 }
 

src/backend/wayland/wl_stubs.c

@@ -60,6 +60,7 @@ unsigned long wl_xdisplay_intern_atom(const char *n) { (void)n; return 0; }
 Display *wl_get_x_display(void) { return NULL; }
 RImage *wl_xwayland_capture_snapshot(WScreen *s, struct wlr_xwayland_surface *xw) { (void)s; (void)xw; return NULL; }
 float wl_xwayland_get_window_opacity(WNativeWindow cw) { (void)cw; return 1.0f; }
+void wl_register_error_handlers(void) {}
 RContext *wl_create_rcontext(int screen_number, RContextAttributes *attribs)
 { (void)screen_number; return RCreateContextWayland(1920, 1080, attribs); }
 #if USE_XWAYLAND
@@ -412,8 +413,8 @@ const WMBackend wl_backend = {
     .cursors_init           = wl_cursors_init,
     .cursor_create_named    = wl_cursor_create_named,
     .shape_combine_mask     = wl_shape_combine_mask,
+.register_error_handlers = wl_register_error_handlers,
 #if USE_XWAYLAND
-    .register_error_handlers = wl_register_error_handlers,
     .texture_create_gc      = wl_texture_create_gc,
     .texture_free_gc        = wl_texture_free_gc,
 #endif

src/main.c

@@ -788,9 +788,13 @@ static int real_main(int argc, char **argv)
 	}
 
 	/* open display */
+	fprintf(stderr, "TRACE: before display_open\n");
 	dpy = (Display *)wm_backend->display_open(DisplayName);
+	fprintf(stderr, "TRACE: after display_open, dpy=%p\n", dpy);
 	wm_backend->display_post_open(DisplayName, &multiHead);
+	fprintf(stderr, "TRACE: before StartUp\n");
 	StartUp(!multiHead);
+	fprintf(stderr, "TRACE: after StartUp\n");
 
 	if (w_global.screen_count == 1)
 		multiHead = False;

src/startup.c

@@ -278,14 +278,16 @@ void StartUp(Bool defaultScreenOnly)
 
 	memset(&wKeyBindings, 0, sizeof(wKeyBindings));
 
+	fprintf(stderr, "TRACE: StartUp before context_init\n");
 	wm_backend->context_init();
-
+	fprintf(stderr, "TRACE: StartUp after context_init, before atoms\n");
 	{
 		int ai;
 		for (ai = 0; ai < (int)wlengthof(atomNames); ai++)
 			atom[ai] = (WMNativeAtom)wm_backend->atom_intern(atomNames[ai]);
 	}
-
+	fprintf(stderr, "TRACE: StartUp after atoms\n");
+	fprintf(stderr, "TRACE: StartUp xdnd_init\n");
 	w_global.atom.wm.state = atom[0];
 	w_global.atom.wm.change_state = atom[1];
 	w_global.atom.wm.protocols = atom[2];
@@ -313,10 +315,14 @@ void StartUp(Bool defaultScreenOnly)
 
 	w_global.atom.wm.ignore_focus_events = atom[21];
 
+fprintf(stderr, "TRACE: StartUp before xdnd_init\n");
 	wm_backend->xdnd_init();
+	fprintf(stderr, "TRACE: StartUp after xdnd_init\n");
 
+	fprintf(stderr, "TRACE: StartUp before cursors_init\n");
 	/* cursors */
 	wm_backend->cursors_init();
+	fprintf(stderr, "TRACE: StartUp after cursors_init\n");
 
 	/* emergency exit... */
 	sig_action.sa_handler = handleSig;