https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78737
--- Comment #20 from janus at gcc dot gnu.org --- (In reply to Damian Rouson from comment #19) > > On thinking about it, is the specific instance of write_formatted allowed? > > I believe not. Note 7.50 of the 31 August 2016 draft Fortran 2015 standard > includes the following: > > "The dynamic type of an object cannot be abstract; therefore, a deferred > type-bound procedure cannot be invoked." > > I interpret the above quote to mean that write_formatted as written in > comment #15 cannot be invoked. Presumably that also means it is invalid > code. I'm not so sure here. Actually I tend to believe that comment 15 as such is valid. It just has two different things that (incidentally) share the same name (which is not forbidden in this context): 1) The deferred TBP 'write_formatted' of the type 'object'. As it is deferred, it has no implementation in that type and can only be invoked polymorphically. 2) The subroutine 'write_formatted' in the module 'object_interface'. I don't see anything that would prevent you from defining a subroutine in this way, but it simply cannot be interpreted as the implementation of the deferred TBP. But then gfortran's runtime-interpretation of this code is wrong. It prints (with Paul's patch) write_formatted => 99 write_formatted2 => 99 since it calls 'write_formatted' as a DTIO procedure of the type 'object', which it is not! I think the correct output would only consist of the second line: write_formatted2 => 99
