patch for gc of interned String

Fri Mar 16 23:03:00 GMT 2001

I was having a String mysteriously turn into another String.
I finally noticed that the intern'd string table is allocated
using _Jv_AllocBytes, which means the GC does not search for
pointers in it. That is ok - but what is not ok was that
when an interned String is collected, there is nothing to
remove it from the intern table - the code that does so is
commented out ... Ooops.
Does this look like a reasonable fix? I especially would
like Hans's opinion, of course. Basically we want the
intern table to be a "weak set", and this seems like a simple
way to do so, but it depends on the cost of finalizers.
 * String.java (unintern): Remove method.
 * natString.cc (unintern): Make into a regular static function,
 instead of a method.
 (intern): Register unintern as a finalizer.
Index: natString.cc
===================================================================
RCS file: /cvs/gcc/gcc/libjava/java/lang/natString.cc,v
retrieving revision 1.16
diff -u -r1.16 natString.cc

--- natString.cc	2000年12月02日 00:28:44	1.16
+++ natString.cc	2001年03月17日 06:55:36
@@ -150,6 +150,19 @@
 }
 }
 
+/* Called by String fake finalizer. */
+static void
+::unintern (jobject obj)
+{
+ JvSynchronize sync (&StringClass);
+ jstring str = reinterpret_cast<jstring> (obj);
+ jstring* ptr = _Jv_StringGetSlot(str);
+ if (*ptr == NULL || *ptr == DELETED_STRING)
+ return;
+ *ptr = DELETED_STRING;
+ strhash_count--;
+}
+
 jstring
 java::lang::String::intern()
 {
@@ -163,21 +176,8 @@
 strhash_count++;
 *ptr = this;
 // When string is GC'd, clear the slot in the hash table.
- // _Jv_RegisterFinalizer ((void *) this, unintern);
+ _Jv_RegisterFinalizer ((void *) this, ::unintern);
 return this;
-}
-
-/* Called by String fake finalizer. */
-void
-java::lang::String::unintern (jobject obj)
-{
- JvSynchronize sync (&StringClass);
- jstring str = reinterpret_cast<jstring> (obj);
- jstring* ptr = _Jv_StringGetSlot(str);
- if (*ptr == NULL || *ptr == DELETED_STRING)
- return;
- *ptr = DELETED_STRING;
- strhash_count--;
 }
 
 jstring
Index: String.java
===================================================================
RCS file: /cvs/gcc/gcc/libjava/java/lang/String.java,v
retrieving revision 1.12
diff -u -r1.12 String.java
--- String.java	2000年11月18日 02:29:13	1.12
+++ String.java	2001年03月17日 06:55:36
@@ -347,6 +347,5 @@
 private native void init (byte[] chars, int hibyte, int offset, int count);
 private native void init (byte[] chars, int offset, int count, String enc)
 throws UnsupportedEncodingException;
- private static native void unintern (Object obj);
 private static native void rehash ();
 }
-- 
	--Per Bothner
per@bothner.com http://www.bothner.com/~per/
