mruby/mruby — pull request #623 by liancheng (2012-12-12 13:22:42+00:00)
Title: Call mrb_gc_arena_save/mrb_gc_arena_restore when proper

I noticed that code in `vm.c` and `codegen.c` were saving and restoring the `arena_idx` field of some `mrb_state` by directly manipulating `arena_idx`. To show the semantics more explicitly, I think it would be better to call `mrb_gc_arena_save` and `mrb_gc_arena_restore` here.

To reduce the cost of the additional function calls, `mrb_gc_arena_save` and `mrb_gc_arena_restore` may be written as macros or inlined functions (if necessary).