I see this was discussed previously here: Bug in nvfortran with -Mchkptr for unallocated optional arguments?
There was some discussion about adding a sub-option but it seems it never went anywhere, could we revive it?
I am using this feature where null pointers can be passed to optional values and be considered not present when interfacing C and Fortran code. I can pass null pointers to signify that an optional value is not present.