warning: NULL used in arithmetic

[satyaakam goswami]

Hi,
     c++ code which used to link with gcc3.2.3, failed with gcc4.1.1,
the error is
"warning: NULL used in arithmetic" , found  searching on web that NULL
should be changed to 0 to avoid this error , my questions is why the
link should fail when we have just the warnings, is this normal
behaviour in gcc4.1.1 to fail on warnings.

Satya