common: Add znew/znew_n() macros

include/common/mem.h

@@ -11,6 +11,17 @@
  */
 void *xzalloc(size_t size);
 
+/*
+ * Type-safe macros in the style of C++ new/new[].
+ * <expr> may be either a type name or value expression.
+ *
+ * Examples:
+ *   struct wlr_box *box = znew(*box);
+ *   char *buf = znew_n(char, 80);
+ */
+#define znew(expr)       ((__typeof__(expr) *)xzalloc(sizeof(expr)))
+#define znew_n(expr, n)  ((__typeof__(expr) *)xzalloc((n) * sizeof(expr)))
+
 /*
  * As defined in FreeBSD.
  * Like realloc(), but calls exit() on error.