early class GC?

Wed Jul 10 22:05:00 GMT 2002

On 2002年7月10日, Jeff Sturm wrote:
> So my hunch is that if two interpreted classes hash to the same chain, one
> will be vulnerable to premature collection. I suppose one could create a
> testcase by loading two classes of the same name, e.g.:

Here's a testcase. It fails as predicted on i686-linux with gcj 3.1,
finalizing 9 of 10 instances, all of which are reachable from their
respective classloaders. (Oddly, it finalized all 10 instances when
compiled to bytecode and executed with gij.)
I'll see about a patch shortly.
public class T extends ClassLoader {
 static T[] a = new T[10];
 byte[] code = {
 -54,-2,-70,-66,0,3,0,45,0,32,1,0,1,67,7,0,
 1,1,0,16,106,97,118,97,47,108,97,110,103,47,79,98,
 106,101,99,116,7,0,3,1,0,1,99,1,0,3,76,67,
 59,1,0,6,60,105,110,105,116,62,1,0,3,40,41,86,
 1,0,4,67,111,100,101,12,0,7,0,8,10,0,4,0,
 10,12,0,5,0,6,9,0,2,0,12,1,0,15,76,105,
 110,101,78,117,109,98,101,114,84,97,98,108,101,1,0,8,
 102,105,110,97,108,105,122,101,1,0,16,106,97,118,97,47,
 108,97,110,103,47,83,121,115,116,101,109,7,0,16,1,0,
 3,111,117,116,1,0,21,76,106,97,118,97,47,105,111,47,
 80,114,105,110,116,83,116,114,101,97,109,59,12,0,18,0,
 19,9,0,17,0,20,1,0,9,102,105,110,97,108,105,122,
 101,100,8,0,22,1,0,19,106,97,118,97,47,105,111,47,
 80,114,105,110,116,83,116,114,101,97,109,7,0,24,1,0,
 7,112,114,105,110,116,108,110,1,0,21,40,76,106,97,118,
 97,47,108,97,110,103,47,83,116,114,105,110,103,59,41,86,
 12,0,26,0,27,10,0,25,0,28,1,0,10,83,111,117,
 114,99,101,70,105,108,101,1,0,6,67,46,106,97,118,97,
 0,33,0,2,0,4,0,0,0,1,0,10,0,5,0,6,
 0,0,0,2,0,1,0,7,0,8,0,1,0,9,0,0,
 0,33,0,1,0,1,0,0,0,9,42,-73,0,11,42,-77,
 0,13,-79,0,0,0,1,0,14,0,0,0,6,0,1,0,
 4,0,5,0,4,0,15,0,8,0,1,0,9,0,0,0,
 33,0,2,0,1,0,0,0,9,-78,0,21,18,23,-74,0,
 29,-79,0,0,0,1,0,14,0,0,0,6,0,1,0,0,
 0,9,0,1,0,30,0,0,0,2,0,31
 };
 T() throws Throwable {
 defineClass("C", code, 0, code.length).newInstance();
 }
 public static void main(String[] args) {
 Runtime r = Runtime.getRuntime();
 try {
 for (int n = 0; n < a.length; n++) {
 a[n] = new T();
 r.gc();
 r.runFinalization();
 Thread.yield();
 }
 } catch (Throwable t) {
 t.printStackTrace();
 }
 }
}