1 files changed, 30 insertions, 6 deletions

diff --git a/symbol.c b/symbol.c
index a3422501a8..b7df410187 100644
--- a/symbol.c
+++ b/symbol.c
@@ -19,6 +19,9 @@
 #ifndef SYMBOL_DEBUG
 # define SYMBOL_DEBUG 0
 #endif
+#ifndef CHECK_ID_SERIAL
+# define CHECK_ID_SERIAL SYMBOL_DEBUG
+#endif
 
 #define SYMBOL_PINNED_P(sym) (RSYMBOL(sym)->id&~ID_SCOPE_MASK)
 
@@ -370,20 +373,41 @@ set_id_entry(rb_id_serial_t num, VALUE str, VALUE sym)
 }
 
 static VALUE
-get_id_entry(rb_id_serial_t num, const enum id_entry_type t)
+get_id_serial_entry(rb_id_serial_t num, ID id, const enum id_entry_type t)
 {
     if (num && num <= global_symbols.last_id) {
 	size_t idx = num / ID_ENTRY_UNIT;
 	VALUE ids = global_symbols.ids;
 	VALUE ary;
 	if (idx < (size_t)RARRAY_LEN(ids) && !NIL_P(ary = rb_ary_entry(ids, (long)idx))) {
-	    VALUE result = rb_ary_entry(ary, (long)(num % ID_ENTRY_UNIT) * ID_ENTRY_SIZE + t);
-	    if (!NIL_P(result)) return result;
+            long pos = (long)(num % ID_ENTRY_UNIT) * ID_ENTRY_SIZE;
+            VALUE result = rb_ary_entry(ary, pos + t);
+            if (NIL_P(result)) return 0;
+#if CHECK_ID_SERIAL
+            if (id) {
+                VALUE sym = result;
+                if (t != ID_ENTRY_SYM)
+                    sym = rb_ary_entry(ary, pos + ID_ENTRY_SYM);
+                if (STATIC_SYM_P(sym)) {
+                    if (STATIC_SYM2ID(sym) != id) return 0;
+                }
+                else {
+                    if (RSYMBOL(sym)->id != id) return 0;
+                }
+            }
+#endif
+            return result;
 	}
     }
     return 0;
 }
 
+static VALUE
+get_id_entry(ID id, const enum id_entry_type t)
+{
+    return get_id_serial_entry(rb_id_to_serial(id), id, t);
+}
+
 static inline ID
 #ifdef __GNUC__
 __attribute__((unused))
@@ -391,7 +415,7 @@ __attribute__((unused))
 rb_id_serial_to_id(rb_id_serial_t num)
 {
     if (is_notop_id((ID)num)) {
-	VALUE sym = get_id_entry(num, ID_ENTRY_SYM);
+        VALUE sym = get_id_serial_entry(num, 0, ID_ENTRY_SYM);
 	return SYM2ID(sym);
     }
     else {
@@ -579,7 +603,7 @@ lookup_str_sym(const VALUE str)
 static VALUE
 lookup_id_str(ID id)
 {
-    return get_id_entry(rb_id_to_serial(id), ID_ENTRY_STR);
+    return get_id_entry(id, ID_ENTRY_STR);
 }
 
 ID
@@ -758,7 +782,7 @@ VALUE
 rb_id2sym(ID x)
 {
     if (!DYNAMIC_ID_P(x)) return STATIC_ID2SYM(x);
-    return get_id_entry(rb_id_to_serial(x), ID_ENTRY_SYM);
+    return get_id_entry(x, ID_ENTRY_SYM);
 }