hash.c: add arity check for Hash#default_proc (and Hash.new); fix mruby#6484

Author: matz

src/hash.c

@@ -11,6 +11,7 @@
 #include <mruby/hash.h>
 #include <mruby/string.h>
 #include <mruby/variable.h>
+#include <mruby/proc.h>
 #include <mruby/internal.h>
 #include <mruby/presym.h>
 
@@ -1273,6 +1274,21 @@ mrb_hash_set(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value val)
   mrb_field_write_barrier_value(mrb, mrb_basic_ptr(hash), key);
   mrb_field_write_barrier_value(mrb, mrb_basic_ptr(hash), val);
 }
+static void
+hash_set_default_proc(mrb_state *mrb, mrb_value hash, mrb_value proc)
+{
+  struct RProc *p = mrb_proc_ptr(proc);
+  if (MRB_PROC_STRICT_P(p)) {
+    int n = mrb_proc_arity(p);
+    if (n != 2 && (n >= 0 || n < -3)) {
+      if (n < 0) n = -n-1;
+      mrb_raisef(mrb, E_TYPE_ERROR, "default_proc takes two arguments (2 for %d)", n);
+    }
+  }
+  mrb_iv_set(mrb, hash, MRB_SYM(ifnone), proc);
+  RHASH(hash)->flags |= MRB_HASH_PROC_DEFAULT;
+  RHASH(hash)->flags |= MRB_HASH_DEFAULT;
+}
 
 /* 15.2.13.4.16 */
 /*
@@ -1323,10 +1339,10 @@ mrb_hash_init(mrb_state *mrb, mrb_value hash)
     if (ifnone_p) {
       mrb_argnum_error(mrb, 1, 0, 0);
     }
-    RHASH(hash)->flags |= MRB_HASH_PROC_DEFAULT;
-    ifnone = block;
+    hash_set_default_proc(mrb, hash, block);
+    return hash;
   }
-  if (!mrb_nil_p(ifnone)) {
+  if (ifnone_p && !mrb_nil_p(ifnone)) {
     RHASH(hash)->flags |= MRB_HASH_DEFAULT;
     mrb_iv_set(mrb, hash, MRB_SYM(ifnone), ifnone);
   }
@@ -1482,14 +1498,12 @@ mrb_hash_set_default_proc(mrb_state *mrb, mrb_value hash)
   }
   mrb_iv_set(mrb, hash, MRB_SYM(ifnone), ifnone);
   if (!mrb_nil_p(ifnone)) {
-    RHASH(hash)->flags |= MRB_HASH_PROC_DEFAULT;
-    RHASH(hash)->flags |= MRB_HASH_DEFAULT;
+    hash_set_default_proc(mrb, hash, ifnone);
   }
   else {
     RHASH(hash)->flags &= ~MRB_HASH_DEFAULT;
     RHASH(hash)->flags &= ~MRB_HASH_PROC_DEFAULT;
   }
-
   return ifnone;
 }