Move MRB_GC_ARENA_SIZE to gc.h and fix compiler warnings

include/mruby.h

@@ -65,10 +65,6 @@ struct mrb_state;
  */
 typedef void* (*mrb_allocf) (struct mrb_state *mrb, void*, size_t, void *ud);
 
-#ifndef MRB_GC_ARENA_SIZE
-#define MRB_GC_ARENA_SIZE 100
-#endif
-
 #ifndef MRB_FIXED_STATE_ATEXIT_STACK_SIZE
 #define MRB_FIXED_STATE_ATEXIT_STACK_SIZE 5
 #endif

include/mruby/gc.h

@@ -30,6 +30,10 @@ MRB_API void mrb_free_context(struct mrb_state *mrb, struct mrb_context *c);
 #define MRB_GC_WHITES (MRB_GC_WHITE_A | MRB_GC_WHITE_B)
 #define MRB_GC_COLOR_MASK 7
 
+#ifndef MRB_GC_ARENA_SIZE
+#define MRB_GC_ARENA_SIZE 100
+#endif
+
 typedef enum {
   GC_STATE_ROOT = 0,
   GC_STATE_MARK,
@@ -75,7 +79,7 @@ typedef struct mrb_gc {
 } mrb_gc;
 
 MRB_API mrb_bool
-mrb_object_dead_p(struct mrb_state *mrb, struct RObject *object);
+mrb_object_dead_p(struct mrb_state *mrb, struct RBasic *object);
 
 MRB_END_DECL
 

src/gc.c

@@ -260,7 +260,7 @@ mrb_free(mrb_state *mrb, void *p)
 }
 
 MRB_API mrb_bool
-mrb_object_dead_p(mrb_state *mrb, struct RObject *object) {
+mrb_object_dead_p(mrb_state *mrb, struct RBasic *object) {
   return is_dead(&mrb->gc, object);
 }
 
@@ -394,7 +394,7 @@ gc_protect(mrb_state *mrb, mrb_gc *gc, struct RBasic *p)
   if (gc->arena_idx >= MRB_GC_ARENA_SIZE) {
     /* arena overflow error */
     gc->arena_idx = MRB_GC_ARENA_SIZE - 4; /* force room in arena */
-    mrb_raise(gc, E_RUNTIME_ERROR, "arena overflow error");
+    mrb_raise(mrb, E_RUNTIME_ERROR, "arena overflow error");
   }
 #else
   if (gc->arena_idx >= gc->arena_capa) {