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### 4.2 Fortran 2008 status

The latest version of the Fortran standard is ISO/IEC 1539-1:2010, informally known as Fortran 2008. The official version is available from International Organization for Standardization (ISO) or its national member organizations. The the final draft (FDIS) can be downloaded free of charge from http://www.nag.co.uk/sc22wg5/links.html. Fortran is developed by the Working Group 5 of Sub-Committee 22 of the Joint Technical Committee 1 of the International Organization for Standardization and the International Electrotechnical Commission (IEC). This group is known as WG5.

The GNU Fortran compiler supports several of the new features of Fortran 2008; the wiki has some information about the current Fortran 2008 implementation status. In particular, the following is implemented.

- The `-std=f2008` option and support for the file extensions `.f08` and `.F08`.
- The `OPEN` statement now supports the `NEWUNIT=` option, which returns a unique file unit, thus preventing inadvertent use of the same unit in different parts of the program.
- The `g0` format descriptor and unlimited format items.
- The mathematical intrinsics `ASINH`, `ACOSH`, `ATANH`, `ERF`, `ERFC`, `GAMMA`, `LOG_GAMMA`, `BESSEL_J0`, `BESSEL_J1`, `BESSEL_JN`, `BESSEL_Y0`, `BESSEL_Y1`, `BESSEL_YN`, `HYPOT`, `NORM2`, and `ERFC_SCALED`.
- Using complex arguments with `TAN`, `SINH`, `COSH`, `TANH`, `ASIN`, `ACOS`, and `ATAN` is now possible; `ATAN`(Y,X) is now an alias for `ATAN2`(Y,X).
- Support of the `PARITY` intrinsic functions.
- The following bit intrinsics: `LEADZ` and `TRAILZ` for counting the number of leading and trailing zero bits, `POPCNT` and `POPPAR` for counting the number of one bits and returning the parity; `BGE`, `BGT`, `BLE`, and `BLT` for bitwise comparisons; `DSHIFTL` and `DSHIFTR` for combined left and right shifts, `MASKL` and `MASKR` for simple left and right justified masks, `MERGE_BITS` for a bitwise merge using a mask, `SHIFTA`, `SHIFTL` and `SHIFTR` for shift operations, and the transformational bit intrinsics `IALL`, `IANY` and `IPARITY`.
- Support of the `EXECUTE_COMMAND_LINE` intrinsic subroutine.
- Support for the `STORAGE_SIZE` intrinsic inquiry function.
- The `INT{8,16,32}` and `REAL{32,64,128}` kind type parameters and the array-valued named constants `INTEGER_KINDS`, `LOGICAL_KINDS`, `REAL_KINDS` and `CHARACTER_KINDS` of the intrinsic module `ISO_FORTRAN_ENV`.
- The module procedures `C_SIZEOF` of the intrinsic module `ISO_C_BINDINGS` and `COMPILER_VERSION` and `COMPILER_OPTIONS` of `ISO_FORTRAN_ENV`.
- Coarray support for serial programs with `-fcoarray=single` flag and experimental support for multiple images with the `-fcoarray=lib` flag.
- The `DO CONCURRENT` construct is supported.
- The `BLOCK` construct is supported.
- The `STOP` and the new `ERROR STOP` statements now support all constant expressions. Both show the signals which were signaling at termination.
- Support for the `CONTIGUOUS` attribute.
- Support for `ALLOCATE` with `MOLD`.
- Support for the `IMPURE` attribute for procedures, which allows for `ELEMENTAL` procedures without the restrictions of `PURE`.
- Null pointers (including `NULL()`) and not-allocated variables can be used as actual argument to optional non-pointer, non-allocatable dummy arguments, denoting an absent argument.
- Non-pointer variables with `TARGET` attribute can be used as actual argument to `POINTER` dummies with `INTENT(IN)`.
- Pointers including procedure pointers and those in a derived type (pointer components) can now be initialized by a target instead of only by `NULL`.
- The `EXIT` statement (with construct-name) can be now be used to leave not only the `DO` but also the `ASSOCIATE`, `BLOCK`, `IF`, `SELECT CASE` and `SELECT TYPE` constructs.
- Internal procedures can now be used as actual argument.
- Minor features: obsolesce diagnostics for `ENTRY` with `-std=f2008`; a line may start with a semicolon; for internal and module procedures `END` can be used instead of `END SUBROUTINE` and `END FUNCTION`; `SELECTED_REAL_KIND` now also takes a `RADIX` argument; intrinsic types are supported for `TYPE`(intrinsic-type-spec); multiple type-bound procedures can be declared in a single `PROCEDURE` statement; implied-shape arrays are supported for named constants (`PARAMETER`).

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