The GNU Fortran Compiler: Fortran 2018 status

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#### 1.3.4 Fortran 2018 status

Fortran 2018 (ISO/IEC 1539:2018) is the most recent version of the Fortran language standard. GNU Fortran implements some of the new features of this standard:

- All Fortran 2018 features derived from ISO/IEC TS 29113:2012, “Further Interoperability of Fortran with C”, are supported by GNU Fortran. This includes assumed-type and assumed-rank objects and the `SELECT RANK` construct as well as the parts relating to `BIND(C)` functions. See also Further Interoperability of Fortran with C.
- GNU Fortran supports a subset of features derived from ISO/IEC TS 18508:2015, “Additional Parallel Features in Fortran”:
  - The new atomic ADD, CAS, FETCH and ADD/OR/XOR, OR and XOR intrinsics.
  - The `CO_MIN` and `CO_MAX` and `SUM` reduction intrinsics, and the `CO_BROADCAST` and `CO_REDUCE` intrinsic, except that those do not support polymorphic types or types with allocatable, pointer or polymorphic components.
  - Events (`EVENT POST`, `EVENT WAIT`, `EVENT_QUERY`).
  - Failed images (`FAIL IMAGE`, `IMAGE_STATUS`, `FAILED_IMAGES`, `STOPPED_IMAGES`).
- An `ERROR STOP` statement is permitted in a `PURE` procedure.
- GNU Fortran supports the `IMPLICIT NONE` statement with an `implicit-none-spec-list`.
- The behavior of the `INQUIRE` statement with the `RECL=` specifier now conforms to Fortran 2018.