par2cmdline (Commandline implementation of PARv2.0 specification)

par2cmdline is a GPL-licensed commandline tool for creating and using PAR2 
parity sets to detect damage in files and repair them if necessary. The 
program uses Reed Solomon Coding to perform its error correction. A useful 
program for checking and ensuring the integrity of binaries retrieved from 
usenet for instance.

This program, or it's argued gcc, has compile issues which result in a 
"Warning: ignoring..." messages during the build process.  This problem is 
known and was made a gcc bug, which was shortly fixed.  From what I know,
this issue does not affect the actual compilation of the program. 

For information on the issue see these messages:
  http://gcc.gnu.org/ml/gcc-bugs/2004-04/msg02848.html
  http://gcc.gnu.org/ml/gcc-bugs/2004-04/msg02856.html 
  http://bugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=356548

There is also current work being done on a par2 library extracted from 
par2cmdline called libpar2 and is available at pararchive.sourceforge.net. 
However, since it still contains the original par2cmdline, it has the same 
compilation issue. 

On a side note, par2cmdline in combination with unrar (available here on 
SlackBuilds.org) can be used by the python program hellanzb to make getting, 
verifying and unraring files with a nzb file almost totally hands-free. 
For more information see: http://www.hellanzb.com/trac/.