[Box] Unroll the changes using features for 4.1

box.c

@@ -299,7 +299,7 @@ box_entry_free(void *ptr)
     cleanup_all_local_extensions(box->ruby_dln_libmap);
 
     free_box_st_tables(ptr);
-    SIZED_FREE(box);
+    xfree((void *)box);
 }
 
 static size_t
@@ -426,9 +426,6 @@ box_initialize(VALUE box_value)
         }
     }
 
-    // Invalidate ZJIT code that assumes only the root box is active
-    rb_zjit_invalidate_root_box();
-
     return box_value;
 }
 

ruby.c

@@ -1818,6 +1818,13 @@ ruby_opt_init(ruby_cmdline_options_t *opt)
 
     if (opt->dump & dump_exit_bits) return;
 
+    /* [Feature #19785] Warning for removed GC environment variable.
+     * Remove this in Ruby 3.4. */
+    if (getenv("RUBY_GC_HEAP_INIT_SLOTS")) {
+        rb_warn_deprecated("The environment variable RUBY_GC_HEAP_INIT_SLOTS",
+                           "environment variables RUBY_GC_HEAP_%d_INIT_SLOTS");
+    }
+
     Init_ext(); /* load statically linked extensions before rubygems */
     Init_extra_exts();