Hi, Hui Zhu I have saw the link you gave me, but I stll cannot figure out how to run gdb with LD_PRELOAD. Can you give me an example in my case? Thanks! Regards, chenwj -- Wei-Ren Chen (陳韋任) Parallel Processing Lab, Institute of Information Science, Academia Sinica, Taiwan (R.O.C.) Tel:886-2-2788-3799 #1667