cache mrb_regexp_p(); ref #980

include/mruby.h

@@ -124,9 +124,13 @@ typedef struct {
 
 typedef void (*mrb_atexit_func)(struct mrb_state*);
 
+#define MRB_STATE_NO_REGEXP 1
+#define MRB_STATE_REGEXP    2
+
 typedef struct mrb_state {
   struct mrb_jmpbuf *jmp;
 
+  uint32_t flags;
   mrb_allocf allocf;                      /* memory allocation function */
   void *allocf_ud;                        /* auxiliary data of allocf */
 

src/etc.c

@@ -179,7 +179,18 @@ mrb_word_boxing_cptr_value(mrb_state *mrb, void *p)
 MRB_API mrb_bool
 mrb_regexp_p(mrb_state *mrb, mrb_value v)
 {
-  return mrb_class_defined(mrb, REGEXP_CLASS) && mrb_obj_is_kind_of(mrb, v, mrb_class_get(mrb, REGEXP_CLASS));
+  if (mrb->flags & MRB_STATE_NO_REGEXP) {
+    return FALSE;
+  }
+  if ((mrb->flags & MRB_STATE_REGEXP) || mrb_class_defined(mrb, REGEXP_CLASS)) {
+    mrb->flags |= MRB_STATE_REGEXP;
+    return mrb_obj_is_kind_of(mrb, v, mrb_class_get(mrb, REGEXP_CLASS));
+  }
+  else {
+    mrb->flags |= MRB_STATE_REGEXP;
+    mrb->flags |= MRB_STATE_NO_REGEXP;
+  }
+  return FALSE;
 }
 
 #if defined _MSC_VER && _MSC_VER < 1900