https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103496
--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> --- (In reply to anlauf from comment #1) > https://j3-fortran.org/doc/year/21/21-134r2.txt > but it still requires using interoperable types etc. > Just asking: did you simply forget to "decorate" your declarations? If you talk about something like 'kind=c_int': On most systems, c_int == c_int32_t == 4 - and gfortran has (by default) a default integer == 4. But also 'kind=8' is very likely to be interoperable; whether it is with c_long or only c_int64_t or ... does not really matter in case of c_sizeof – we just need to know that some C type exists, which is interoperable. [Likewise, integer(kind=c_int128_t) may or may not be interoperable, depending whether that kind is available - and if not, c_int128_t should be a negative number. (Ignoring for now that c_int128_t is a vendor extension.)] But granted, usually you want to be sure that kind matches a specific C integer type and then c_... becomes useful and more portable. * * * 'interoperable type': I have to admit that I tend to get confused whether * "18.3.5 Interoperability of array variables" applies or whether also * "18.3.6 Interoperability of procedures and procedure interfaces" applies. In the latter case, array descriptors are permitted - and that permits allocatables, pointer, sub-sections etc. The former is more restrictive by only permitting explicit shape or assumed size – while the latter permits more. Given that the current wording for c_sizeof is about "that is not an assumed-size array or an assumed-rank array that is associated with an assumed-size array." I think one reasonable reading is that 18.3.6 applies as 18.3.5 does not permit assumed rank. As 21-134r2 shows, the current wording is not ideal – but at the end, the modification just implies that 18.3.5 applies (IMHO).
