Prevent alloc errors from crashing in `list_t`

This commit changes the `list_t` api so that alloc errors can be
detected and worked around. Also fixes errors not found in 5cc7342

backend/drm/drm.c

@@ -748,8 +748,13 @@ void wlr_drm_scan_connectors(struct wlr_drm_backend *backend) {
 			parse_edid(&output->output, edid_len, edid);
 			free(edid);
 
+			if (list_add(backend->outputs, output) == -1) {
+				wlr_log_errno(L_ERROR, "Allocation failed");
+				drmModeFreeConnector(conn);
+				free(output);
+				continue;
+			}
 			wlr_output_create_global(&output->output, backend->display);
-			list_add(backend->outputs, output);
 			wlr_log(L_INFO, "Found display '%s'", output->output.name);
 		} else {
 			output = backend->outputs->items[index];
@@ -764,6 +769,10 @@ void wlr_drm_scan_connectors(struct wlr_drm_backend *backend) {
 			for (int i = 0; i < conn->count_modes; ++i) {
 				struct wlr_drm_output_mode *mode = calloc(1,
 						sizeof(struct wlr_drm_output_mode));
+				if (!mode) {
+					wlr_log_errno(L_ERROR, "Allocation failed");
+					continue;
+				}
 				mode->mode = conn->modes[i];
 				mode->wlr_mode.width = mode->mode.hdisplay;
 				mode->wlr_mode.height = mode->mode.vdisplay;
@@ -773,7 +782,11 @@ void wlr_drm_scan_connectors(struct wlr_drm_backend *backend) {
 					mode->wlr_mode.width, mode->wlr_mode.height,
 					mode->wlr_mode.refresh);
 
-				list_add(output->output.modes, mode);
+				if (list_add(backend->outputs, output) == -1) {
+					wlr_log_errno(L_ERROR, "Allocation failed");
+					free(mode);
+					continue;
+				}
 			}
 
 			output->state = WLR_DRM_OUTPUT_NEEDS_MODESET;

backend/libinput/events.c

@@ -44,11 +44,14 @@ static struct wlr_input_device *allocate_device(
 		return NULL;
 	}
 	struct wlr_input_device *wlr_dev = &wlr_libinput_dev->wlr_input_device;
+	if (list_add(wlr_devices, wlr_dev) == -1) {
+		free(wlr_libinput_dev);
+		return NULL;
+	}
 	wlr_libinput_dev->handle = libinput_dev;
 	libinput_device_ref(libinput_dev);
 	wlr_input_device_init(wlr_dev, type, &input_device_impl,
 			name, vendor, product);
-	list_add(wlr_devices, wlr_dev);
 	return wlr_dev;
 }
 

backend/multi/backend.c

@@ -120,6 +120,12 @@ void wlr_multi_backend_add(struct wlr_backend *_multi,
 		wlr_log(L_ERROR, "Could not add backend: allocation failed");
 		return;
 	}
+	if (list_add(multi->backends, sub) == -1) {
+		wlr_log(L_ERROR, "Could not add backend: allocation failed");
+		free(sub);
+		return;
+	}
+
 	sub->backend = backend;
 	sub->container = &multi->backend;
 
@@ -137,8 +143,6 @@ void wlr_multi_backend_add(struct wlr_backend *_multi,
 	wl_signal_add(&backend->events.input_remove, &sub->input_remove);
 	wl_signal_add(&backend->events.output_add, &sub->output_add);
 	wl_signal_add(&backend->events.output_remove, &sub->output_remove);
-
-	list_add(multi->backends, sub);
 }
 
 struct wlr_session *wlr_multi_get_session(struct wlr_backend *_backend) {

backend/wayland/output.c

@@ -236,7 +236,8 @@ struct wlr_output *wlr_wl_output_create(struct wlr_backend *_backend) {
 		output->egl_surface, output->egl_surface,
 		output->backend->egl.context)) {
 		wlr_log(L_ERROR, "eglMakeCurrent failed: %s", egl_error());
-		return false;
+		free(output);
+		return NULL;
 	}
 
 	glViewport(0, 0, wlr_output->width, wlr_output->height);
@@ -248,11 +249,16 @@ struct wlr_output *wlr_wl_output_create(struct wlr_backend *_backend) {
 
 	if (!eglSwapBuffers(output->backend->egl.display, output->egl_surface)) {
 		wlr_log(L_ERROR, "eglSwapBuffers failed: %s", egl_error());
-		return false;
+		free(output);
+		return NULL;
 	}
 
+	if (list_add(backend->outputs, wlr_output) == -1) {
+		wlr_log(L_ERROR, "Allocation failed");
+		free(output);
+		return NULL;
+	}
 	wlr_output_create_global(wlr_output, backend->local_display);
-	list_add(backend->outputs, wlr_output);
 	wl_signal_emit(&backend->backend.events.output_add, wlr_output);
 	return wlr_output;
 }

backend/wayland/wl_seat.c

@@ -188,7 +188,7 @@ static struct wlr_input_device *allocate_device(struct wlr_wl_backend *backend,
 		enum wlr_input_device_type type) {
 	struct wlr_wl_input_device *wlr_wl_dev;
 	if (!(wlr_wl_dev = calloc(1, sizeof(struct wlr_wl_input_device)))) {
-		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		wlr_log_errno(L_ERROR, "Allocation failed");
 		return NULL;
 	}
 
@@ -200,7 +200,11 @@ static struct wlr_input_device *allocate_device(struct wlr_wl_backend *backend,
 	struct wlr_input_device *wlr_device = &wlr_wl_dev->wlr_input_device;
 	wlr_input_device_init(wlr_device, type, &input_device_impl,
 			name, vendor, product);
-	list_add(backend->devices, wlr_device);
+	if (list_add(backend->devices, wlr_device) == -1) {
+		wlr_log_errno(L_ERROR, "Allocation failed");
+		free(wlr_wl_dev);
+		return NULL;
+	}
 	return wlr_device;
 }
 

examples/touch.c

@@ -65,7 +65,9 @@ static void handle_touch_down(struct touch_state *tstate, int32_t slot,
 	point->slot = slot;
 	point->x = x / width;
 	point->y = y / height;
-	list_add(sample->touch_points, point);
+	if (list_add(sample->touch_points, point) == -1) {
+		free(point);
+	}
 }
 
 static void handle_touch_up(struct touch_state *tstate, int32_t slot) {

include/wlr/util/list.h

@@ -9,16 +9,45 @@ typedef struct {
 	void **items;
 } list_t;
 
+/**
+ * Creates a new list, may return `NULL` on failure
+ */
 list_t *list_create(void);
 void list_free(list_t *list);
 void list_foreach(list_t *list, void (*callback)(void *item));
-void list_add(list_t *list, void *item);
+/**
-void list_push(list_t *list, void *item);
+ * Add `item` to the end of a list.
-void list_insert(list_t *list, size_t index, void *item);
+ * Returns: new list length or `-1` on failure
+ */
+int list_add(list_t *list, void *item);
+/**
+ * Add `item` to the end of a list.
+ * Returns: new list length or `-1` on failure
+ */
+int list_push(list_t *list, void *item);
+/**
+ * Place `item` into index `index` in the list
+ * Returns: new list length or `-1` on failure
+ */
+int list_insert(list_t *list, size_t index, void *item);
+/**
+ * Remove an item from the list
+ */
 void list_del(list_t *list, size_t index);
+/**
+ * Remove and return an item from the end of the list
+ */
 void *list_pop(list_t *list);
+/**
+ * Get a reference to the last item of a list without removal
+ */
 void *list_peek(list_t *list);
-void list_cat(list_t *list, list_t *source);
+/**
+ * Append each item in `source` to `list`
+ * Does not modify `source`
+ * Returns: new list length or `-1` on failure
+ */
+int list_cat(list_t *list, list_t *source);
 // See qsort. Remember to use *_qsort functions as compare functions,
 // because they dereference the left and right arguments first!
 void list_qsort(list_t *list, int compare(const void *left, const void *right));

util/list.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <string.h>
 #include <stddef.h>
 #include <wlr/util/list.h>
@@ -19,11 +20,16 @@ list_t *list_create(void) {
 	return list;
 }
 
-static void list_resize(list_t *list) {
+static bool list_resize(list_t *list) {
 	if (list->length == list->capacity) {
-		list->capacity += 10;
+		void *new_items = realloc(list->items, sizeof(void*) * (list->capacity + 10));
-		list->items = realloc(list->items, sizeof(void*) * list->capacity);
+		if (!new_items) {
+			return false;
 		}
+		list->capacity += 10;
+		list->items = new_items;
+	}
+	return true;
 }
 
 void list_free(list_t *list) {
@@ -43,20 +49,26 @@ void list_foreach(list_t *list, void (*callback)(void *item)) {
 	}
 }
 
-void list_add(list_t *list, void *item) {
+int list_add(list_t *list, void *item) {
-	list_resize(list);
+	if (!list_resize(list)) {
+		return -1;
+	}
 	list->items[list->length++] = item;
+	return list->length;
 }
 
-void list_push(list_t *list, void *item) {
+int list_push(list_t *list, void *item) {
-	list_add(list, item);
+	return list_add(list, item);
 }
 
-void list_insert(list_t *list, size_t index, void *item) {
+int list_insert(list_t *list, size_t index, void *item) {
-	list_resize(list);
+	if (!list_resize(list)) {
+		return -1;
+	}
 	memmove(&list->items[index + 1], &list->items[index], sizeof(void*) * (list->length - index));
 	list->length++;
 	list->items[index] = item;
+	return list->length;
 }
 
 void list_del(list_t *list, size_t index) {
@@ -74,11 +86,16 @@ void *list_peek(list_t *list) {
 	return list->items[list->length - 1];
 }
 
-void list_cat(list_t *list, list_t *source) {
+int list_cat(list_t *list, list_t *source) {
+	size_t old_len = list->length;
 	size_t i;
 	for (i = 0; i < source->length; ++i) {
-		list_add(list, source->items[i]);
+		if (list_add(list, source->items[i]) == -1) {
+			list->length = old_len;
+			return -1;
 		}
+	}
+	return list->length;
 }
 
 void list_qsort(list_t *list, int compare(const void *left, const void *right)) {