fix: Qt6 Wayland crash — root cause identified, kded6 fix deployed

ROOT CAUSE: Qt6's auto-generated Wayland wrappers pass NULL proxies to wl_*_add_listener() during initialization. The generated code stores wlRegistryBind() return value in m_wl_* member without null check, then init_listener() calls wl_*_add_listener(m_wl_*, ...) which page-faults at null+8 (write to proxy->object.implementation). FIX (kded6): wrapper script renames libqwayland.so to .disabled before launching kded6.real. QT_QPA_PLATFORM=offscreen alone is not sufficient — Qt6 still loads wayland plugin despite env var. FIX (libwayland): null guards in redox.patch for wl_proxy_add_listener, wl_proxy_get_version, wl_proxy_get_display. Blocked from compilation by pre-existing relibc conflicts (open_memstream, signalfd_siginfo). FIX (Qt6 wrappers): regex-based null guard insertion proven in concept. Blocked by TOML recipe format not supporting backslash escape sequences. Implementation plan: inject null guards via a separate build step script rather than inline in recipe.toml.
2026-05-06 16:34:46 +01:00
parent 8c51508362
commit 36c8c3d95a
37 changed files with 1057 additions and 321 deletions
@@ -0,0 +1,46 @@
+/* Runtime null guard for wl_proxy_add_listener — interposed via LD_PRELOAD.
+ * Qt6 Wayland QPA passes NULL proxies during initialization on Redox.
+ * This shim prevents the page fault at null+8 (proxy->object.implementation)
+ * by returning an error code instead of crashing.
+ *
+ * Cross-referenced with libwayland wayland-client.c:649.
+ */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+/* Original function pointer */
+static int (*real_wl_proxy_add_listener)(void *proxy,
+    void (**implementation)(void), void *data) = NULL;
+
+static void *(*real_wl_proxy_get_display)(void *proxy) = NULL;
+static unsigned int (*real_wl_proxy_get_version)(void *proxy) = NULL;
+
+static void init(void) {
+    real_wl_proxy_add_listener = dlsym(RTLD_NEXT, "wl_proxy_add_listener");
+    real_wl_proxy_get_display = dlsym(RTLD_NEXT, "wl_proxy_get_display");
+    real_wl_proxy_get_version = dlsym(RTLD_NEXT, "wl_proxy_get_version");
+}
+
+int wl_proxy_add_listener(void *proxy,
+    void (**implementation)(void), void *data) {
+    if (!real_wl_proxy_add_listener) init();
+    if (!proxy) {
+        fprintf(stderr, "wayland-guard: wl_proxy_add_listener(NULL) prevented crash\n");
+        return -1;
+    }
+    return real_wl_proxy_add_listener(proxy, implementation, data);
+}
+
+void *wl_proxy_get_display(void *proxy) {
+    if (!real_wl_proxy_get_display) init();
+    if (!proxy) return NULL;
+    return real_wl_proxy_get_display(proxy);
+}
+
+unsigned int wl_proxy_get_version(void *proxy) {
+    if (!real_wl_proxy_get_version) init();
+    if (!proxy) return 0;
+    return real_wl_proxy_get_version(proxy);
+}