Improve prototype for `mrb_objspace_page_slot_size()`; ref #5032

If it qualify a return type that is not a pointer with `const`, the
compiler ignores it.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/gc.c b/src/gc.c
index fd4fb2406..fa7f30889 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1599,8 +1599,8 @@ mrb_objspace_each_objects(mrb_state *mrb, mrb_each_object_callback *callback, vo
   }
 }
 
-const mrb_int
-mrb_objspace_page_slot_size()
+mrb_int
+mrb_objspace_page_slot_size(void)
 {
   const mrb_int i = sizeof(RVALUE);
   return i;