Well, if I find some time, maybe I can fix this. But I need for info to find out the problem. Could you run lamip with gdb and post the backtrace here?

$ gdb lamip
(gdb) run
SIGSEGV received
(gdb) backtrace

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 182901310624 (LWP 15798)]
0x0000002a95a2a288 in __gconv_get_alias_db () from /lib/libc.so.6

(gdb) thread apply all bt

Thread 2 (Thread 1082128752 (LWP 15801)):
#0 0x0000002a957774e4 in pthread_cond_wait@@GLIBC_2.3.2 ()
from /lib/libpthread.so.0
#1 0x0000000000406eae in _signal_thread ()
#2 0x0000002a95774b55 in start_thread () from /lib/libpthread.so.0
#3 0x0000002a95adb870 in clone () from /lib/libc.so.6
#4 0x0000000000000000 in ?? ()
#5 0x0000000000000000 in ?? ()
#6 0x0000000000000000 in ?? ()
#7 0x0000000000000000 in ?? ()
#8 0x0000000000000000 in ?? ()
#9 0x0000000000000000 in ?? ()
#10 0x0000000000000000 in ?? ()
#11 0x0000000000000000 in ?? ()
#12 0x0000002a95c2ae80 in __check_rhosts_file () from /lib/libc.so.6
...
#38 0x0000002a9587d1d0 in stack_cache () from /lib/libpthread.so.0
#39 0x0000002a9587d1d0 in stack_cache () from /lib/libpthread.so.0
...
#148 0x0000000000406de5 in queue_out ()
...
now here go the endless:
#217 0x108e8b4800000408 in ?? ()

forgot backtrace:
#0 0x0000002a95a2a288 in __gconv_get_alias_db () from /lib/libc.so.6
(gdb) backtrace
#0 0x0000002a95a2a288 in __gconv_get_alias_db () from /lib/libc.so.6
#1 0x0000002a95a273d9 in iconv_close () from /lib/libc.so.6
#2 0x0000002a95a269d7 in iconv () from /lib/libc.so.6
#3 0x0000002a98fc2e02 in from_native_encoding ()
from /usr/lib/lamip/libfoobar.so
#4 0x0000002a98fc348d in tagz_parser_real () from /usr/lib/lamip/libfoobar.so
#5 0x0000002a98fbb745 in update_display () from /usr/lib/lamip/libfoobar.so
#6 0x0000002a9698691f in gtk_tree_model_rows_reordered ()
from /usr/lib/libgtk-x11-2.0.so.0
#7 0x0000002a96986a26 in gtk_tree_model_foreach ()
from /usr/lib/libgtk-x11-2.0.so.0
#8 0x0000002a98fbb33a in fpl_update () from /usr/lib/lamip/libfoobar.so
#9 0x0000002a98fb90cf in foo_mainwin_setup () from /usr/lib/lamip/libfoobar.so
#10 0x0000002a98fb5750 in run () from /usr/lib/lamip/libfoobar.so
#11 0x00000000004069e1 in _ct_thread ()
#12 0x0000000000404a98 in lamip_run_control ()
#13 0x00000000004048bd in main ()

I checked the arguments I passed to iconv() in from_native_encoding(), and they seem fine.

Could you try:
$ iconv -f utf8 -t ucs-4le <some-file-in-utf8-encoding>
and see if it receives segfault?

Or is someone else having this problem too?

>>iconv -f utf8 -t ucs-4le <some-file-in-utf8-encoding>

works flawlessly

after reinstalling ubuntu it seems to work. I'll continue testing

now i get "String is null (BUG)"

I added some printf:
http://www.olv.idv.tw/~olvaffe/tmp/unicode.patch

Could you apply this and see what it says?

it keeps saying "conversion failed"

There must be some invalid byte sequence (maybe from %metadata%) in the input.

Does this happen for any input, even pure ascii or even when the formatting string is "abcdefgh"?