mtrace not showing line number

Hi,

I have a problem similar to this one http://www.linuxselfhelp.com/forum/viewtopic.phtml?t=2937
I am trying to use mtrace to see where in the source file the double
free is occuring and
still mtrace only shows me pointer addresses.
I'm using
mtrace tests mtrace.log
the code I'm compiling is written in c++
.