Does &((struct name *)NULL -> b) cause undefined behaviour in C11?

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From a lawyer point of view, the expression &(((struct name *)NULL)->b); should lead to UB, since you could not find a path in which there would be no UB. IMHO the root cause is that at a moment you apply the -> operator on an expression that does not point to an object.

From a compiler point of view, assuming the compiler programmer was not overcomplicated, it is clear that the expression returns the same value as offsetof(name, b) would, and I’m pretty sure that provided it is compiled without error any existing compiler will give that result.

As written, we could not blame a compiler that would note that in the inner part you use operator -> on an expression than cannot point to an object (since it is null) and issue a warning or an error.

My conclusion is that until there is a special paragraph saying that provided it is only to take its address it is legal do dereference a null pointer, this expression is not legal C.

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