Implementation-defined as far as I'm aware. If pointers with all bits zero actually represent null pointers, things will be fine. edit: I haven't found any sm

Implementation-defined as far as I'm aware. If pointers with all bits zero actually represent null pointers, things will be fine. edit: I haven't found any smoking gun quotation in the C11 standard on short notice, but there is footnote 296 (p.348) on calloc() zeroing all bits: > Note that this need not be the same as the representation of floating-point zero or a null pointer constant. Nothing about this being UB in cases where it does represent a null pointer constant.