Extended interoperation with C

Standardized support of C language interface use, as defined in Fortran 2003, is nowadays implemented in most Fortran compilers. However, there are significant limitations to this interoperability, particularly with respect to Fortran objects for which no C analog exists. Furthermore, the language semantics as defined up to Fortran 2008 do not allow for a conforming implementation of the Message Passing Interface (MPI, [1]) which presently is the most prevalent parallelization approach on large-scale HPC systems. Therefore, a decision was made by the Fortran Standards Committee to develop a Technical Specification (ISO/IEC TS 29113 [2], referred to as “TS” in the following) that significantly extends the scope of the interoperation facilities; this work was concluded in 2012 by a successful WG5 ballot, and the TS was published by ISO shortly afterwards. This article provides an informal overview of the new facilities, which are also targeted for integration into the next release of the Fortran standard, with additional technical corrections if necessary.