libgcj/3523: java.io.LineNumberReader has a buggy reset() method.

[jwnimmer@alum.mit.edu]

>Number:         3523
>Category:       libgcj
>Synopsis:       java.io.LineNumberReader has a buggy reset() method.
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jul 01 19:56:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Jeremy Nimmer
>Release:        gcc version 3.1 20010630 (experimental)
>Organization:
>Environment:
i686-pc-linux-gnu, configured with: configure --enable-threads=posix --enable-shared --enable-languages=c++,java
>Description:
The implementation of the reset() method in java.io.LineNumberReader passes invalid arguments to the countLines method, causing it to index the array out of bounds under certain circumstances.
>How-To-Repeat:
Compile this program to bytecode (with javac, jikes, or gcj) and then run with gij.

import java.io.*;
public class CrashLNR {
  public static void main(String[] args)
    throws Exception
  {
    String s = "123456789\n123456789\n1234\n1234\n";
    LineNumberReader r = new LineNumberReader(new StringReader(s), 35);
    r.readLine();
    r.readLine();
    r.mark(10);
    r.readLine();
    r.reset(); // exception
  }
}
>Fix:
Here is my suggested patch, but I have not tested it thoroughly.

% diff -u LineNumberReader.java LineNumberReader.java.fixed
--- LineNumberReader.java       Tue Mar  7 14:55:26 2000
+++ LineNumberReader.java.fixed Sun Jul  1 22:27:14 2001
@@ -94,7 +94,7 @@
        if (markPos > 0 && pos > markPos && buffer[markPos-1] == '\r'
            && buffer[markPos] == '\n')
          lineNumber--;
-       lineNumber -= countLines(buffer, pos, markPos);
+       lineNumber -= countLines(buffer, markPos, pos-markPos);
        pos = markPos;
       }
   }
>Release-Note:
>Audit-Trail:
>Unformatted: