GCC translates the expression into the offset of the field port_list as intended, but doing this involves dereferencing a NULL-pointer (evaluates to 0). The expression can only be correct if one assumes that the dereference will be optimized away - why is it safe to assume that?
this is similar to the offsetof(...) macro (stddef.h). but basically it (the offsetof macro at-least) works like this [consider a shorter sample "& ((S *0) ->foo) )"]: 1. (( S *)0) : takes the integer zero and casts it as a pointer to S. 2. ((S *)0)->foo: dereferences that pointer to point to structure member foo. 3. &(((S *)0)->foo): computes the address of foo does that make any sense ? kind regards anupam -- In the beginning was the lambda, and the lambda was with Emacs, and Emacs was the lambda. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
