When alloc size is too large, only allocate struct

struct.c

@@ -849,7 +849,7 @@ struct_alloc(VALUE klass)
         return (VALUE)st;
     }
     else {
-        NEWOBJ_OF(st, struct RStruct, klass, flags, embedded_size, 0);
+        NEWOBJ_OF(st, struct RStruct, klass, flags, sizeof(struct RStruct), 0);
 
         st->as.heap.ptr = struct_heap_alloc((VALUE)st, n);
         rb_mem_clear((VALUE *)st->as.heap.ptr, n);

test/ruby/test_struct.rb

@@ -41,6 +41,14 @@ module TestStruct
     end
   end
 
+  def test_larger_than_largest_pool
+    count = (GC::INTERNAL_CONSTANTS[:RVARGC_MAX_ALLOCATE_SIZE] / RbConfig::SIZEOF["void*"]) + 1
+    list = Array(0..count)
+    klass = @Struct.new(*list.map { |i| :"a_#{i}"})
+    struct = klass.new(*list)
+    assert_equal 0, struct.a_0
+  end
+
   def test_small_structs
     names = [:a, :b, :c, :d]
     1.upto(4) {|n|