For more info, it seems fine on Solaris with dbx.

bash-3.00# dbx ./sample
For information about new features see `help changes'
To remove this message, put `dbxenv suppress_startup_message 7.5' in your .dbxrc
Reading sample
Reading ld.so.1
Reading libsocket.so.1
Reading libnsl.so.1
Reading libm.so.2
Reading librt.so.1
Reading libpthread.so.1
Reading libc.so.1
Reading libaio.so.1
Reading libmd5.so.1
(dbx) stop in initsig
dbx: warning: 'initsig' has no debugger info -- will trigger on first instructio n
(2) stop in initsig
(dbx) run
Running: sample
(process id 18817)
t@1 (l@1) stopped in initsig at 0x08aae794
0x08aae794: initsig       :     pushl    %ebp
(dbx) where
current thread: t@1
=>[1] initsig(0x8047310, 0x80471e0, 0xd13fb840, 0x8a8002f, 0x0, 0xd1250408), at 0x8aae794
  [2] main(0x1, 0x8047224, 0x804722c), at 0x8a80073
(dbx) threads
*>    t@1  a  l@1   ?()   breakpoint       in  initsig()
(dbx) catch
INT QUIT ILL TRAP ABRT BUS SEGV SYS PIPE TERM USR1 USR2 PWR URG POLL STOP TTIN T TOU VTALRM PROF XCPU XFSZ FREEZE THAW LOST XRES 39 40 RTMIN RTMIN+1 RTMIN+2 RTMI N+3 RTMIN+4 RTMIN+5 RTMIN+6 RTMIN+7
(dbx) cont -sig SIGINT
t@null (l@null) terminating signal 2 SIGINT
(dbx) where
dbx: program is not active
(dbx)