Embedding Ruby in C is poor documented part of Ruby programming. When I
call Ruby from C code and I do something wrong on Ruby side I get error
in this form:

<dummy toplevel>:17: [BUG] Segmentation fault
ruby 1.9.0 (2008-10-04 revision 19669) [i486-linux]

-- control frame ----------
c:0002 p:---- s:0004 b:0004 l:000003 d:000003 CFUNC  :require
c:0001 p:0000 s:0002 b:0002 l:000001 d:000001 TOP    <dummy toplevel>:17
---------------------------
DBG> : ":0:in `require'"
-- backtrace of native function call (Use addr2line) --
0x231316
0x1515e7
0x15166a
0x1da144
0x8e6410
0x3ca46c
0x1530da
0x153473
0x15009b
0x156127
0x1566c6
0x21ef73
0x22b56a
0x22c4a5
0x80540fb
0x80544ee
0x3b6bd6
0x8049721
-------------------------------------------------------
My first question is if its possible to get more sophisticated error
message? What does Use addr2line mean? Or how can I find from this stack
trace, where is my error?

Output of addr2line:
$ addr2line -e ./Debug/traffic_profiller < addrs ??:0 ??:0 ??:0 ??:0
??:0 ??:0 ??:0 ??:0 ??:0 ??:0 ??:0 ??:0 ??:0 ??:0
/home/matej/Programming/doschecker/traffic_profiller/Debug/../src/traffic_profiller.c:398
/home/matej/Programming/doschecker/traffic_profiller/Debug/../src/traffic_profiller.c:490
??:0 ??:0 

Which points me to ends of two methods, but in this case I know, where
the problem is and this output doesnt say me anything about it.

Second question is about using gems in embedded Ruby. When I use it in
classic Ruby form require name_of_gem the gem is not found. When I use
absolute path to one file gem its OK, but when gem is composed from more
files I wasnt able to use it.