Is serialization broken?

Fri Jan 26 04:19:00 GMT 2001

On 2001年1月26日, Barnet Wagman wrote:
> I'm getting an erroneous ClassCastException deserializing an object with
> gcj, gcc version 2.97 20010117 (experimental).
>> With the test program SerTest.java (below)...

Well, it seems that java.io.DataInputStream.readInt is throwing an
EOFException because it is mistakenly reading some negative data to mean
EOF. I was able to jump past the check for the negative value in the
debugger and the program ran to completion just fine.
Breakpoint 2, java.util.HashMap.readObject (this=@8101fc8, s=@8086400)
 at /home/warrenl/egcs/libjava/java/util/HashMap.java:639
639 s.defaultReadObject();
(gdb) n
641 int capacity = s.readInt();
(gdb) 
642 int len = s.readInt();
(gdb) s
java.io.ObjectInputStream.readInt (this=@8086400)
 at /home/warrenl/egcs/libjava/java/io/ObjectInputStream.java:651
651 return this.dataInputStream.readInt ();
(gdb) 
java.io.DataInputStream.readInt (this=@8066f00)
 at /home/warrenl/egcs/libjava/java/io/DataInputStream.java:293
293 int a = in.read();
(gdb) n
294 int b = in.read();
(gdb) 
295 int c = in.read();
(gdb) 
296 int d = in.read();
(gdb) 
297 if (d < 0)
(gdb) p d
6ドル = -24
(gdb) l
292 {
293 int a = in.read();
294 int b = in.read();
295 int c = in.read();
296 int d = in.read();
297 if (d < 0)
298 throw new EOFException();
299 
300 return (((a & 0xff) << 24) | ((b & 0xff) << 16) |
301 ((c & 0xff) << 8) | (d & 0xff));
(gdb) 
It'll take a bit more poking around to see how to properly avoid that < 0
check (that'll have to wait till at least after I've had some sleep ;-).
--warrenl