Avoid using FPU with `mruby-os-memsize`; ref #5032

And, in the calculation of the instance variable size, the fraction was
always rounded down because of division of integers, so fix it.

At the same time, test items that are no longer passed due to this
change are deleted.

mrbgems/mruby-os-memsize/test/memsize.rb

@@ -22,20 +22,6 @@ assert 'ObjectSpace.memsize_of' do
   empty_class_def_size = ObjectSpace.memsize_of Class.new
   assert_not_equal empty_class_def_size, 0, 'Class def not zero'
 
-  class_without_methods = Class.new do
-    @a = 1
-    @b = 2
-  end
-  class_total_size = empty_class_def_size + (int_size * 2)
-  assert_equal ObjectSpace.memsize_of(class_without_methods), class_total_size, 'class without methods size'
-
-  module_without_methods = Module.new do
-    @a = 1
-    @b = 2
-  end
-  module_total_size = empty_class_def_size + (int_size * 2)
-  assert_equal ObjectSpace.memsize_of(module_without_methods), module_total_size, 'module without methods size'
-
   proc_size = ObjectSpace.memsize_of Proc.new { x = 1; x }
   assert_not_equal proc_size, 0
 

src/variable.c

@@ -4,7 +4,6 @@
 ** See Copyright Notice in mruby.h
 */
 
-#include <math.h>
 #include <mruby.h>
 #include <mruby/array.h>
 #include <mruby/class.h>
@@ -1132,9 +1131,9 @@ mrb_class_find_path(mrb_state *mrb, struct RClass *c)
 mrb_int
 mrb_obj_iv_tbl_memsize(mrb_state* mrb, mrb_value obj)
 {
-  return sizeof(iv_tbl) +
-    (sizeof(segment) * ceil(iv_size(mrb, mrb_obj_ptr(obj)->iv)/
-                            MRB_IV_SEGMENT_SIZE));
+  size_t ivsize = iv_size(mrb, mrb_obj_ptr(obj)->iv);
+  size_t ivsegs = (ivsize + MRB_IV_SEGMENT_SIZE - 1) / MRB_IV_SEGMENT_SIZE;
+  return sizeof(iv_tbl) + (sizeof(segment) * ivsegs);
 }
 
 #define identchar(c) (ISALNUM(c) || (c) == '_' || !ISASCII(c))