On Mon, Jan 26, 2009 at 11:52 PM, <zol...@bendor.com.au> wrote: > I was debugging a function and by inserting the debug statement crashed > the system. Some investigation revealed that gcc 4.3.2 arm-eabi (compiled > from sources) with -O2 under some circumstances assumes that if a pointer > is dereferenced, it can not be NULL therefore explicite tests against > NULL can be later eliminated.
That's an optimization permitted by the language standard, but possibly unhelpful on your particular target. It is a case of a more general situation: the compiler can assume that code containing "undefined behavior" (such as a null-pointer dereference) is not executed, or equivalently that a condition that would lead to the execution of UB is always false. I don't know how much work it would be to disable this optimization in gcc. -- James
