* include/ruby/intern.h: declare rb_hash_tbl.

* include/ruby/ruby.h (RHash): delay st_table allocation.
  rename tbl field to ntbl to detect direct reference to the st_table
  as a compile error.
  (RHASH_TBL): abstract accessor defined.
  (RHASH_ITER_LEV): ditto.
  (RHASH_IFNONE): ditto.
  (RHASH_SIZE): ditto.
  (RHASH_EMPTY_P): ditto.

* hash.c: delay st_table allocation.

* gc.c: replace tbl by ntbl.

* array.c: replace direct field accessor by abstract field accessor
  such as RHASH(hash)->tbl to RHASH_TBL(hash).

* marshal.c: ditto.

* insns.def: ditto.

* ext/iconv/iconv.c: ditto.

* ext/json/ext/generator/generator.c: ditto.

* ext/json/ext/parser/parser.c: ditto.

* ext/syck/rubyext.c: ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13309 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

12 files changed, 136 insertions, 59 deletions

diff --git a/ChangeLog b/ChangeLog
index 475ff0395c..c75125134d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,35 @@
+Thu Aug 30 08:00:12 2007  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/intern.h: declare rb_hash_tbl.
+
+	* include/ruby/ruby.h (RHash): delay st_table allocation.
+	  rename tbl field to ntbl to detect direct reference to the st_table
+	  as a compile error.
+	  (RHASH_TBL): abstract accessor defined.
+	  (RHASH_ITER_LEV): ditto.
+	  (RHASH_IFNONE): ditto.
+	  (RHASH_SIZE): ditto.
+	  (RHASH_EMPTY_P): ditto.
+
+	* hash.c: delay st_table allocation.
+
+	* gc.c: replace tbl by ntbl.
+
+	* array.c: replace direct field accessor by abstract field accessor
+	  such as RHASH(hash)->tbl to RHASH_TBL(hash).
+
+	* marshal.c: ditto.
+
+	* insns.def: ditto.
+
+	* ext/iconv/iconv.c: ditto.
+
+	* ext/json/ext/generator/generator.c: ditto.
+
+	* ext/json/ext/parser/parser.c: ditto.
+
+	* ext/syck/rubyext.c: ditto.
+
 Wed Aug 29 18:36:06 2007  Tanaka Akira  <akr@fsij.org>
 
 	* lib/open-uri.rb: add :ftp_active_mode option.
diff --git a/array.c b/array.c
index 0b4ffa14d7..7718305d5a 100644
--- a/array.c
+++ b/array.c
@@ -2525,7 +2525,7 @@ rb_ary_diff(VALUE ary1, VALUE ary2)
     ary3 = rb_ary_new();
 
     for (i=0; i<RARRAY_LEN(ary1); i++) {
-	if (st_lookup(RHASH(hash)->tbl, RARRAY_PTR(ary1)[i], 0)) continue;
+	if (st_lookup(RHASH_TBL(hash), RARRAY_PTR(ary1)[i], 0)) continue;
 	rb_ary_push(ary3, rb_ary_elt(ary1, i));
     }
     return ary3;
@@ -2553,9 +2553,12 @@ rb_ary_and(VALUE ary1, VALUE ary2)
 	    RARRAY_LEN(ary1) : RARRAY_LEN(ary2));
     hash = ary_make_hash(ary2, 0);
 
+    if (RHASH_EMPTY_P(hash))
+        return ary3;
+
     for (i=0; i<RARRAY_LEN(ary1); i++) {
 	v = vv = rb_ary_elt(ary1, i);
-	if (st_delete(RHASH(hash)->tbl, (st_data_t*)&vv, 0)) {
+	if (st_delete(RHASH_TBL(hash), (st_data_t*)&vv, 0)) {
 	    rb_ary_push(ary3, v);
 	}
     }
@@ -2587,13 +2590,13 @@ rb_ary_or(VALUE ary1, VALUE ary2)
 
     for (i=0; i<RARRAY_LEN(ary1); i++) {
 	v = vv = rb_ary_elt(ary1, i);
-	if (st_delete(RHASH(hash)->tbl, (st_data_t*)&vv, 0)) {
+	if (st_delete(RHASH_TBL(hash), (st_data_t*)&vv, 0)) {
 	    rb_ary_push(ary3, v);
 	}
     }
     for (i=0; i<RARRAY_LEN(ary2); i++) {
 	v = vv = rb_ary_elt(ary2, i);
-	if (st_delete(RHASH(hash)->tbl, (st_data_t*)&vv, 0)) {
+	if (st_delete(RHASH_TBL(hash), (st_data_t*)&vv, 0)) {
 	    rb_ary_push(ary3, v);
 	}
     }
@@ -2623,12 +2626,12 @@ rb_ary_uniq_bang(VALUE ary)
     ary_iter_check(ary);
     hash = ary_make_hash(ary, 0);
 
-    if (RARRAY_LEN(ary) == RHASH(hash)->tbl->num_entries) {
+    if (RARRAY_LEN(ary) == RHASH_SIZE(hash)) {
 	return Qnil;
     }
     for (i=j=0; i<RARRAY_LEN(ary); i++) {
 	v = vv = rb_ary_elt(ary, i);
-	if (st_delete(RHASH(hash)->tbl, (st_data_t*)&vv, 0)) {
+	if (st_delete(RHASH_TBL(hash), (st_data_t*)&vv, 0)) {
 	    rb_ary_store(ary, j++, v);
 	}
     }
diff --git a/ext/iconv/iconv.c b/ext/iconv/iconv.c
index b6bc0a11a5..ccedd0c66d 100644
--- a/ext/iconv/iconv.c
+++ b/ext/iconv/iconv.c
@@ -138,10 +138,10 @@ map_charset(VALUE *code)
 {
     VALUE val = *code;
 
-    if (RHASH(charset_map)->tbl && RHASH(charset_map)->tbl->num_entries) {
+    if (RHASH_SIZE(charset_map)) {
 	VALUE key = rb_funcall2(val, rb_intern("downcase"), 0, 0);
 	StringValuePtr(key);
-	if (st_lookup(RHASH(charset_map)->tbl, key, &val)) {
+	if (st_lookup(RHASH_TBL(charset_map), key, &val)) {
 	    *code = val;
 	}
     }
diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index b08455f223..616832c992 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -86,7 +86,7 @@ static int hash_to_json_state_i(VALUE key, VALUE value, VALUE Vstate)
 }
 
 inline static VALUE mHash_json_transfrom(VALUE self, VALUE Vstate, VALUE Vdepth) {
-    long depth, len = RHASH(self)->tbl->num_entries;
+    long depth, len = RHASH_SIZE(self);
     VALUE result;
     GET_STATE(Vstate);
 
@@ -140,7 +140,7 @@ static VALUE mHash_to_json(int argc, VALUE *argv, VALUE self)
     rb_scan_args(argc, argv, "02", &Vstate, &Vdepth);
     depth = NIL_P(Vdepth) ? 0 : FIX2LONG(Vdepth);
     if (NIL_P(Vstate)) {
-        long len = RHASH(self)->tbl->num_entries;
+        long len = RHASH_SIZE(self);
         result = rb_str_buf_new(len);
         rb_str_buf_cat2(result, "{");
         rb_hash_foreach(self, hash_to_json_i, result);
@@ -480,7 +480,7 @@ static inline VALUE cState_configure(VALUE self, VALUE opts)
         state->object_nl = tmp;
     }
     tmp = ID2SYM(i_check_circular);
-    if (st_lookup(RHASH(opts)->tbl, tmp, 0)) {
+    if (st_lookup(RHASH_TBL(opts), tmp, 0)) {
         tmp = rb_hash_aref(opts, ID2SYM(i_check_circular));
         state->check_circular = RTEST(tmp);
     } else {
@@ -488,7 +488,7 @@ static inline VALUE cState_configure(VALUE self, VALUE opts)
     }
     tmp = ID2SYM(i_max_nesting);
     state->max_nesting = 19;
-    if (st_lookup(RHASH(opts)->tbl, tmp, 0)) {
+    if (st_lookup(RHASH_TBL(opts), tmp, 0)) {
         VALUE max_nesting = rb_hash_aref(opts, tmp);
         if (RTEST(max_nesting)) {
             Check_Type(max_nesting, T_FIXNUM);
diff --git a/ext/json/ext/parser/parser.c b/ext/json/ext/parser/parser.c
index a1950b067a..a6b7021f7e 100644
--- a/ext/json/ext/parser/parser.c
+++ b/ext/json/ext/parser/parser.c
@@ -1470,7 +1470,7 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
             rb_raise(rb_eArgError, "opts needs to be like a hash");
         } else {
             VALUE tmp = ID2SYM(i_max_nesting);
-            if (st_lookup(RHASH(opts)->tbl, tmp, 0)) {
+            if (st_lookup(RHASH_TBL(opts), tmp, 0)) {
                 VALUE max_nesting = rb_hash_aref(opts, tmp);
                 if (RTEST(max_nesting)) {
                     Check_Type(max_nesting, T_FIXNUM);
@@ -1480,7 +1480,7 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
                 }
             }
             tmp = ID2SYM(i_allow_nan);
-            if (st_lookup(RHASH(opts)->tbl, tmp, 0)) {
+            if (st_lookup(RHASH_TBL(opts), tmp, 0)) {
                 VALUE allow_nan = rb_hash_aref(opts, tmp);
                 if (RTEST(allow_nan)) json->allow_nan = 1;
             }
diff --git a/ext/syck/rubyext.c b/ext/syck/rubyext.c
index 9a41c18e8f..53625c91de 100644
--- a/ext/syck/rubyext.c
+++ b/ext/syck/rubyext.c
@@ -621,7 +621,7 @@ rb_syck_load_handler(SyckParser *p, SyckNode *n)
     if ( bonus->taint)      OBJ_TAINT( obj );
     if ( bonus->proc != 0 ) rb_funcall(bonus->proc, s_call, 1, obj);
 
-    rb_hash_aset(bonus->data, INT2FIX(RHASH(bonus->data)->tbl->num_entries), obj);
+    rb_hash_aset(bonus->data, INT2FIX(RHASH_SIZE(bonus->data)), obj);
     return obj;
 }
 
diff --git a/gc.c b/gc.c
index 8054d9acb3..7d521eb07a 100644
--- a/gc.c
+++ b/gc.c
@@ -1032,7 +1032,7 @@ gc_mark_children(VALUE ptr, int lev)
 	break;
 
       case T_HASH:
-	mark_hash(obj->as.hash.tbl, lev);
+	mark_hash(obj->as.hash.ntbl, lev);
 	ptr = obj->as.hash.ifnone;
 	goto again;
 
@@ -1267,8 +1267,8 @@ obj_free(VALUE obj)
 	rb_ary_free(obj);
 	break;
       case T_HASH:
-	if (RANY(obj)->as.hash.tbl) {
-	    st_free_table(RANY(obj)->as.hash.tbl);
+	if (RANY(obj)->as.hash.ntbl) {
+	    st_free_table(RANY(obj)->as.hash.ntbl);
 	}
 	break;
       case T_REGEXP:
diff --git a/hash.c b/hash.c
index 27c0c5bdfc..8fbc7b9416 100644
--- a/hash.c
+++ b/hash.c
@@ -147,10 +147,10 @@ hash_foreach_iter(VALUE key, VALUE value, struct hash_foreach_arg *arg)
     int status;
     st_table *tbl;
 
-    tbl = RHASH(arg->hash)->tbl;
+    tbl = RHASH(arg->hash)->ntbl;
     if (key == Qundef) return ST_CONTINUE;
     status = (*arg->func)(key, value, arg->arg);
-    if (RHASH(arg->hash)->tbl != tbl) {
+    if (RHASH(arg->hash)->ntbl != tbl) {
 	rb_raise(rb_eRuntimeError, "rehash occurred during iteration");
     }
     switch (status) {
@@ -172,7 +172,7 @@ hash_foreach_ensure(VALUE hash)
 
     if (RHASH(hash)->iter_lev == 0) {
 	if (FL_TEST(hash, HASH_DELETED)) {
-	    st_cleanup_safe(RHASH(hash)->tbl, Qundef);
+	    st_cleanup_safe(RHASH(hash)->ntbl, Qundef);
 	    FL_UNSET(hash, HASH_DELETED);
 	}
     }
@@ -182,7 +182,7 @@ hash_foreach_ensure(VALUE hash)
 static VALUE
 hash_foreach_call(struct hash_foreach_arg *arg)
 {
-    if (st_foreach(RHASH(arg->hash)->tbl, hash_foreach_iter, (st_data_t)arg)) {
+    if (st_foreach(RHASH(arg->hash)->ntbl, hash_foreach_iter, (st_data_t)arg)) {
  	rb_raise(rb_eRuntimeError, "hash modified during iteration");
     }
     return Qnil;
@@ -193,6 +193,8 @@ rb_hash_foreach(VALUE hash, int (*func)(ANYARGS), VALUE farg)
 {
     struct hash_foreach_arg arg;
 
+    if (!RHASH(hash)->ntbl)
+        return;
     RHASH(hash)->iter_lev++;
     arg.hash = hash;
     arg.func = (rb_foreach_func *)func;
@@ -216,7 +218,7 @@ hash_alloc(VALUE klass)
 {
     VALUE hash = hash_alloc0(klass);
 
-    RHASH(hash)->tbl = st_init_table(&objhash);
+    RHASH(hash)->ntbl = 0;
 
     return hash;
 }
@@ -228,14 +230,29 @@ rb_hash_new(void)
 }
 
 static void
-rb_hash_modify(VALUE hash)
+rb_hash_modify_check(VALUE hash)
 {
-    if (!RHASH(hash)->tbl) rb_raise(rb_eTypeError, "uninitialized Hash");
     if (OBJ_FROZEN(hash)) rb_error_frozen("hash");
     if (!OBJ_TAINTED(hash) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify hash");
 }
 
+struct st_table *
+rb_hash_tbl(VALUE hash)
+{
+    if (!RHASH(hash)->ntbl) {
+        RHASH(hash)->ntbl = st_init_table(&objhash);
+    }
+    return RHASH(hash)->ntbl;
+}
+
+static void
+rb_hash_modify(VALUE hash)
+{
+    rb_hash_modify_check(hash);
+    rb_hash_tbl(hash);
+}
+
 /*
  *  call-seq:
  *     Hash.new                          => hash
@@ -313,7 +330,9 @@ rb_hash_s_create(int argc, VALUE *argv, VALUE klass)
 
     if (argc == 1 && TYPE(argv[0]) == T_HASH) {
 	hash = hash_alloc0(klass);
-	RHASH(hash)->tbl = st_copy(RHASH(argv[0])->tbl);
+        if (RHASH(argv[0])->ntbl) {
+            RHASH(hash)->ntbl = st_copy(RHASH(argv[0])->ntbl);
+        }
 
 	return hash;
     }
@@ -388,11 +407,13 @@ rb_hash_rehash(VALUE hash)
     if (RHASH(hash)->iter_lev > 0) {
 	rb_raise(rb_eRuntimeError, "rehash during iteration");
     }
-    rb_hash_modify(hash);
-    tbl = st_init_table_with_size(RHASH(hash)->tbl->type, RHASH(hash)->tbl->num_entries);
+    rb_hash_modify_check(hash);
+    if (!RHASH(hash)->ntbl)
+        return hash;
+    tbl = st_init_table_with_size(RHASH(hash)->ntbl->type, RHASH(hash)->ntbl->num_entries);
     rb_hash_foreach(hash, rb_hash_rehash_i, (st_data_t)tbl);
-    st_free_table(RHASH(hash)->tbl);
-    RHASH(hash)->tbl = tbl;
+    st_free_table(RHASH(hash)->ntbl);
+    RHASH(hash)->ntbl = tbl;
 
     return hash;
 }
@@ -416,7 +437,7 @@ rb_hash_aref(VALUE hash, VALUE key)
 {
     VALUE val;
 
-    if (!st_lookup(RHASH(hash)->tbl, key, &val)) {
+    if (!RHASH(hash)->ntbl || !st_lookup(RHASH(hash)->ntbl, key, &val)) {
 	return rb_funcall(hash, id_default, 1, key);
     }
     return val;
@@ -427,7 +448,7 @@ rb_hash_lookup(VALUE hash, VALUE key)
 {
     VALUE val;
 
-    if (!st_lookup(RHASH(hash)->tbl, key, &val)) {
+    if (!RHASH(hash)->ntbl || !st_lookup(RHASH(hash)->ntbl, key, &val)) {
 	return Qnil; /* without Hash#default */
     }
     return val;
@@ -475,7 +496,7 @@ rb_hash_fetch(int argc, VALUE *argv, VALUE hash)
     if (block_given && argc == 2) {
 	rb_warn("block supersedes default value argument");
     }
-    if (!st_lookup(RHASH(hash)->tbl, key, &val)) {
+    if (!RHASH(hash)->ntbl || !st_lookup(RHASH(hash)->ntbl, key, &val)) {
 	if (block_given) return rb_yield(key);
 	if (argc == 1) {
 	    rb_raise(rb_eKeyError, "key not found");
@@ -620,13 +641,15 @@ rb_hash_delete_key(VALUE hash, VALUE key)
 {
     st_data_t ktmp = (st_data_t)key, val;
 
+    if (!RHASH(hash)->ntbl)
+        return Qundef;
     if (RHASH(hash)->iter_lev > 0) {
-	if (st_delete_safe(RHASH(hash)->tbl, &ktmp, &val, Qundef)) {
+	if (st_delete_safe(RHASH(hash)->ntbl, &ktmp, &val, Qundef)) {
 	    FL_SET(hash, HASH_DELETED);
 	    return (VALUE)val;
 	}
     }
-    else if (st_delete(RHASH(hash)->tbl, &ktmp, &val))
+    else if (st_delete(RHASH(hash)->ntbl, &ktmp, &val))
 	return (VALUE)val;
     return Qundef;
 }
@@ -765,9 +788,12 @@ rb_hash_delete_if(VALUE hash)
 VALUE
 rb_hash_reject_bang(VALUE hash)
 {
-    int n = RHASH(hash)->tbl->num_entries;
+    int n;
+    if (!RHASH(hash)->ntbl)
+        return Qnil;
+    n = RHASH(hash)->ntbl->num_entries;
     rb_hash_delete_if(hash);
-    if (n == RHASH(hash)->tbl->num_entries) return Qnil;
+    if (n == RHASH(hash)->ntbl->num_entries) return Qnil;
     return hash;
 }
 
@@ -861,12 +887,14 @@ clear_i(VALUE key, VALUE value, VALUE dummy)
 static VALUE
 rb_hash_clear(VALUE hash)
 {
-    rb_hash_modify(hash);
-    if (RHASH(hash)->tbl->num_entries > 0) {
+    rb_hash_modify_check(hash);
+    if (!RHASH(hash)->ntbl)
+        return hash;
+    if (RHASH(hash)->ntbl->num_entries > 0) {
 	if (RHASH(hash)->iter_lev > 0)
 	    rb_hash_foreach(hash, clear_i, 0);
 	else
-	    st_clear(RHASH(hash)->tbl);
+	    st_clear(RHASH(hash)->ntbl);
     }
 
     return hash;
@@ -894,11 +922,11 @@ VALUE
 rb_hash_aset(VALUE hash, VALUE key, VALUE val)
 {
     rb_hash_modify(hash);
-    if (TYPE(key) != T_STRING || st_lookup(RHASH(hash)->tbl, key, 0)) {
-	st_insert(RHASH(hash)->tbl, key, val);
+    if (TYPE(key) != T_STRING || st_lookup(RHASH(hash)->ntbl, key, 0)) {
+	st_insert(RHASH(hash)->ntbl, key, val);
     }
     else {
-	st_add_direct(RHASH(hash)->tbl, rb_str_new4(key), val);
+	st_add_direct(RHASH(hash)->ntbl, rb_str_new4(key), val);
     }
     return val;
 }
@@ -959,7 +987,9 @@ rb_hash_replace(VALUE hash, VALUE hash2)
 static VALUE
 rb_hash_size(VALUE hash)
 {
-    return INT2FIX(RHASH(hash)->tbl->num_entries);
+    if (!RHASH(hash)->ntbl)
+        return INT2FIX(0);
+    return INT2FIX(RHASH(hash)->ntbl->num_entries);
 }
 
 
@@ -976,9 +1006,7 @@ rb_hash_size(VALUE hash)
 static VALUE
 rb_hash_empty_p(VALUE hash)
 {
-    if (RHASH(hash)->tbl->num_entries == 0)
-	return Qtrue;
-    return Qfalse;
+    return RHASH_EMPTY_P(hash) ? Qtrue : Qfalse;
 }
 
 static int
@@ -1190,7 +1218,7 @@ inspect_hash(VALUE hash, VALUE dummy, int recur)
 static VALUE
 rb_hash_inspect(VALUE hash)
 {
-    if (RHASH(hash)->tbl == 0 || RHASH(hash)->tbl->num_entries == 0)
+    if (RHASH_EMPTY_P(hash))
 	return rb_str_new2("{}");
     return rb_exec_recursive(inspect_hash, hash, 0);
 }
@@ -1288,7 +1316,9 @@ rb_hash_values(VALUE hash)
 static VALUE
 rb_hash_has_key(VALUE hash, VALUE key)
 {
-    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
+    if (!RHASH(hash)->ntbl)
+        return Qfalse;
+    if (st_lookup(RHASH(hash)->ntbl, key, 0)) {
 	return Qtrue;
     }
     return Qfalse;
@@ -1380,15 +1410,17 @@ hash_equal(VALUE hash1, VALUE hash2, int eql)
 	}
 	return rb_equal(hash2, hash1);
     }
-    if (RHASH(hash1)->tbl->num_entries != RHASH(hash2)->tbl->num_entries)
+    if (RHASH_SIZE(hash1) != RHASH_SIZE(hash2))
 	return Qfalse;
+    if (!RHASH(hash1)->ntbl || !RHASH(hash2)->ntbl)
+        return Qtrue;
 #if 0
     if (!(rb_equal(RHASH(hash1)->ifnone, RHASH(hash2)->ifnone) &&
 	  FL_TEST(hash1, HASH_PROC_DEFAULT) == FL_TEST(hash2, HASH_PROC_DEFAULT)))
 	return Qfalse;
 #endif
 
-    data.tbl = RHASH(hash2)->tbl;
+    data.tbl = RHASH(hash2)->ntbl;
     data.result = Qtrue;
     rb_hash_foreach(hash1, eql ? eql_i : equal_i, (st_data_t)&data);
 
@@ -1451,7 +1483,9 @@ recursive_hash(VALUE hash, VALUE dummy, int recur)
     if (recur) {
 	return LONG2FIX(0);
     }
-    hval = RHASH(hash)->tbl->num_entries;
+    if (!RHASH(hash)->ntbl)
+        return LONG2FIX(0);
+    hval = RHASH(hash)->ntbl->num_entries;
     rb_hash_foreach(hash, hash_i, (st_data_t)&hval);
     return INT2FIX(hval);
 }
@@ -1695,7 +1729,7 @@ static VALUE
 rb_hash_compare_by_id(VALUE hash)
 {
     rb_hash_modify(hash);
-    RHASH(hash)->tbl->type = &identhash;
+    RHASH(hash)->ntbl->type = &identhash;
     rb_hash_rehash(hash);
     return hash;
 }
@@ -1712,7 +1746,9 @@ rb_hash_compare_by_id(VALUE hash)
 static VALUE
 rb_hash_compare_by_id_p(VALUE hash)
 {
-    if (RHASH(hash)->tbl->type == &identhash) {
+    if (!RHASH(hash)->ntbl)
+        return Qfalse;
+    if (RHASH(hash)->ntbl->type == &identhash) {
 	return Qtrue;
     }
     return Qfalse;
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 78ac3f9d00..829d732893 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -326,6 +326,7 @@ VALUE rb_hash_lookup(VALUE, VALUE);
 VALUE rb_hash_aset(VALUE, VALUE, VALUE);
 VALUE rb_hash_delete_if(VALUE);
 VALUE rb_hash_delete(VALUE,VALUE);
+struct st_table *rb_hash_tbl(VALUE);
 int rb_path_check(const char*);
 int rb_env_path_tainted(void);
 /* io.c */
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 2dbf29956e..63cb7b417e 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -478,10 +478,15 @@ struct RRegexp {
 
 struct RHash {
     struct RBasic basic;
-    struct st_table *tbl;
+    struct st_table *ntbl;      /* maybe 0 */
     int iter_lev;
     VALUE ifnone;
 };
+#define RHASH_TBL(h) rb_hash_tbl(h)
+#define RHASH_ITER_LEV(h) RHASH(h)->iter_lev
+#define RHASH_IFNONE(h) RHASH(h)->ifnone
+#define RHASH_SIZE(h) (RHASH(h)->ntbl ? RHASH(h)->ntbl->num_entries : 0)
+#define RHASH_EMPTY_P(h) (RHASH_SIZE(h) == 0)
 
 struct RFile {
     struct RBasic basic;
diff --git a/insns.def b/insns.def
index 4a12a5b930..1d9ef3d6f2 100644
--- a/insns.def
+++ b/insns.def
@@ -1312,7 +1312,7 @@ opt_case_dispatch
     }
     else {
 	VALUE val;
-	if (st_lookup(RHASH(hash)->tbl, key, &val)) {
+	if (st_lookup(RHASH_TBL(hash), key, &val)) {
 	    JUMP(FIX2INT(val));
 	}
 	else {
@@ -1958,7 +1958,7 @@ opt_length
 	    val = LONG2NUM(RARRAY_LEN(recv));
 	}
 	else if (HEAP_CLASS_OF(recv) == rb_cHash) {
-	    val = INT2FIX(RHASH(recv)->tbl->num_entries);
+	    val = INT2FIX(RHASH_SIZE(recv));
 	}
 	else {
 	    goto INSN_LABEL(normal_dispatch);
diff --git a/marshal.c b/marshal.c
index b4ba9b6140..79e559d7f3 100644
--- a/marshal.c
+++ b/marshal.c
@@ -578,7 +578,7 @@ w_object(VALUE obj, struct dump_arg *arg, int limit)
 	    else {
 		w_byte(TYPE_HASH_DEF, arg);
 	    }
-	    w_long(RHASH(obj)->tbl->num_entries, arg);
+	    w_long(RHASH_SIZE(obj), arg);
 	    rb_hash_foreach(obj, hash_each, (st_data_t)&c_arg);
 	    if (!NIL_P(RHASH(obj)->ifnone)) {
 		w_object(RHASH(obj)->ifnone, arg, limit);
@@ -899,7 +899,7 @@ r_string(struct load_arg *arg)
 static VALUE
 r_entry(VALUE v, struct load_arg *arg)
 {
-    rb_hash_aset(arg->data, INT2FIX(RHASH(arg->data)->tbl->num_entries), v);
+    rb_hash_aset(arg->data, INT2FIX(RHASH_SIZE(arg->data)), v);
     if (arg->taint) OBJ_TAINT(v);
     if (arg->proc) {
 	v = rb_funcall(arg->proc, rb_intern("call"), 1, v);