C Library problem in Debian

I have been using LLVM on an 32-bit RHEL 5 machine for a while now. I used “printf” in the passes, and the llvm backend was able to compile without any problems. Recently, I tried installing LLVM on Debian 6 (using vmware), and the make process complains that it can’t “printf” in the scope. I am using gcc 4.5 on the RHEL 5, and gcc 4.4 on the Debian 6. I was able to get printf to work with an “include <stdio.h>”, but I am puzzled as to why I have to specify this in Debian but not RHEL 5?
I was wondering if this was a problem with the LD_LIBRARY_PATH, or some flags that I need to change in the build process?