This patch against debian fpc-2.2.2-8 does the following:
When a pascal program is compiled with -gl, then any runtime
error (either internal, caused by caught signal, or runerror())
dumps the stack and then kills itself by SIGABRT.

This is to allow catching runtime errors in gdb.

Details: We want the stack to be as small as possible when sending
SIGABRT. That is why DumpStackAndAbort is a macro and not a function
and why we call syscall using assembly. Another trick we do is
to place abort calls not only in HandleErrorAddrFrame, but in 
fpc_rangecheck, fpc_iocheck, fpc_... too. If a rangecheck fails,
the resulting stack trace is:
(gdb) bt
#0  0x08058409 in fpc_rangeerror ()
#1  0x08048115 in F (I=0) at testp.pas:13

Beware, gdb is not able to decode stack if the abort is called
in HandleErrorAddrFrame. That was another reason why fpc_*chech
methods calls abort themselves, not relying on HandleErrorAddrFrame.