https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107576
--- Comment #8 from anlauf at gcc dot gnu.org --- (In reply to G. Steinmetz from comment #7) > $ gfortran -c z3.f90 > z3.f90:2:10: > > 2 | call s(null()) > | 1 > Error: MOLD argument to NULL required at (1) I think that error message might be fine. It seems to be related to 16.9.144 NULL() and table 16.5: Characteristics of the result of NULL ( ). This is why z3c/z2i give no error: there is an explicit interface, and 16.9.144(5) explains how this is resolved. With gfortran -fallow-argument-mismatch, we have the bad situation that the user explicitly wants to leave the space of standard conformance, and we are entering extension space, with all its problems...