drm_format_set_union: Require initialized dst and remove assert

include/wlr/render/drm_format_set.h

@@ -82,7 +82,8 @@ bool wlr_drm_format_set_intersect(struct wlr_drm_format_set *dst,
 
 /**
  * Unions DRM format set `a` and `b`, storing in the destination set
- * `dst`.
+ * `dst`. The `dst` must either be zeroed or initialized with other state
+ * to be replaced.
  *
  * Returns false on failure.
  */

render/drm_format_set.c

@@ -258,8 +258,6 @@ static bool drm_format_set_extend(struct wlr_drm_format_set *dst,
 
 bool wlr_drm_format_set_union(struct wlr_drm_format_set *dst,
 		const struct wlr_drm_format_set *a, const struct wlr_drm_format_set *b) {
-	assert(dst != a && dst != b);
-
 	struct wlr_drm_format_set out = {0};
 	out.capacity = a->len + b->len;
 	out.formats = calloc(out.capacity, sizeof(struct wlr_drm_format *));
@@ -276,6 +274,7 @@ bool wlr_drm_format_set_union(struct wlr_drm_format_set *dst,
 		return false;
 	}
 
+	wlr_drm_format_set_finish(dst);
 	*dst = out;
 
 	return true;

types/wlr_linux_dmabuf_v1.c

@@ -917,12 +917,9 @@ static bool set_default_feedback(struct wlr_linux_dmabuf_v1 *linux_dmabuf,
 	for (size_t i = 0; i < tranches_len; i++) {
 		const struct wlr_linux_dmabuf_feedback_v1_tranche *tranche = &tranches[i];
 
-		struct wlr_drm_format_set uni;
-		if (!wlr_drm_format_set_union(&uni, &formats, &tranche->formats)) {
+		if (!wlr_drm_format_set_union(&formats, &formats, &tranche->formats)) {
 			goto error_formats;
 		}
-		wlr_drm_format_set_finish(&formats);
-		formats = uni;
 	}
 
 	compiled_feedback_destroy(linux_dmabuf->default_feedback);