Interesting Prof at MIT
David Wingate
http://web.mit.edu/~wingated/www/index.html

Linux memory and 64bit useful commands

file
ulimit

if get error like Program received signal SIGSEGV, Segmentation fault.
0x000000380ee62184 in fwrite () from /lib64/libc.so.6
using gdb for non root user but works fine for root user on
RHEL 5.4

try
export MALLOC_CHECK_=3
and recompile the program with gcc

That should solve the problem