How to use short dashes in program listings?

[Nikos Chantziaras]

When inserting a program listing, all "-" characters in the source code 
are converted to long dashes.  This results in the C operator "--" 
looking more like a single long line rather than two dashes.  (There is 
some space between each dash, but it's so small it only becomes obvious 
when zooming in.)

Is there a way around this?