Well load the app in question in gdb
then
with whatever address is on the bad line.
You can also try to use dwarf vs stabs as symbol info type (project options / debugging // but also for each package)
There are various things that can be wrong.
- the actual line info written by fpc to your app
- the line info reader that fpc adds to your app (unit lineinfo (stabs) or lnfodwrf (dwarf))
there are tools like objdump that may be able to decompile the line info, if you want to go that way.
For a bug report, it would be real important to know where the error is. (And also if released/older fpc has the problem too)