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This document summarizes Fortran standards support in Flang. The information is only provided as a guideline. The TODOs/Not Yet Implemented messages emitted by the compiler for unimplemented features should be treated as authoritative.
The standards support information is provided as a table with three columns that are self explanatory. The Status column uses the letters Y, P, N for the implementation status:
There is no distinction made between support in the Parser/Semantics and the MLIR or Lowering stages.
Note: The two major missing features in Flang at present are coarrays and parameterized derived types (PDTs) with length type parameters.
See document for a brief discussion about the new features in Fortran 2023. The following table summarizes the status of all important Fortran 2023 features. The table entries are based on the document The new features in Fortran 2023.
| Feature | Status | Comments |
|---|---|---|
| Allow longer statement lines and overall statement length | Y | |
| Automatic allocation of lengths of character variables | N | |
| The specifiers typeof and classof | N | |
| Conditional expressions and arguments | N | |
| More use of boz constants | P | All usages other than enum are supported |
| Intrinsics for extracting tokens from a string | N | |
| Intrinsics for Trig functions that work in degrees | Y | |
| Intrinsics for Trig functions that work in half revolutions | Y | |
| Changes to system_clock | N | |
| Changes for conformance with the new IEEE standard | Y | |
| Additional named constants to specify kinds | Y | |
| Extensions for c_f_pointer intrinsic | Y | |
| Procedures for converting between fortran and c strings | N | |
| The at edit descriptor | N | |
| Control over leading zeros in output of real values | N | |
| Extensions for Namelist | N | |
| Allow an object of a type with a coarray ultimate component to be an array or allocatable | N | |
| Put with Notify | N | |
| Error conditions in collectives | N | |
| Simple procedures | N | |
| Using integer arrays to specify subscripts | N | |
| Using integer arrays to specify rank and bound of an array | N | |
| Using an integer constant to specify rank | N | |
| Reduction specifier for do concurrent | P | Syntax is accepted |
| Enumerations | N |
All features except those listed in the following table are supported. Almost all of the unsupported features are related to the multi-image execution. The table entries are based on the document The new features in Fortran 2018.
| Feature | Status | Comments |
|---|---|---|
| Asynchronous communication | P | Syntax is accepted |
| Teams | N | Multi-image/Coarray feature |
| Image failure | P | Multi-image/Coarray feature. stat_failed_image is added |
| Form team statement | N | Multi-image/Coarray feature |
| Change team construct | N | Multi-image/Coarray feature |
| Coarrays allocated in teams | N | Multi-image/Coarray feature |
| Critical construct | N | Multi-image/Coarray feature |
| Lock and unlock statements | N | Multi-image/Coarray feature |
| Events | N | Multi-image/Coarray feature |
| Sync team construct | N | Multi-image/Coarray feature |
| Image selectors | N | Multi-image/Coarray feature |
| Intrinsic functions get_team and team_number | N | Multi-image/Coarray feature |
| Intrinsic function image_index | N | Multi-image/Coarray feature |
| Intrinsic function num_images | N | Multi-image/Coarray feature |
| Intrinsic function this_image | N | Multi-image/Coarray feature |
| Intrinsic move_alloc extensions | P | Multi-image/Coarray feature |
| Detecting failed and stopped images | N | Multi-image/Coarray feature |
| Collective subroutines | N | Multi-image/Coarray feature |
| New and enhanced atomic subroutines | N | Multi-image/Coarray feature |
| Failed images and stat= specifiers | N | Multi-image/Coarray feature |
| Intrinsic function coshape | N | Multi-image/Coarray feature |
All features except those listed in the following table are supported.
| Feature | Status | Comments |
|---|---|---|
| Coarrays | N | Lowering and runtime support is not implemented |
| do concurrent | P | Sequential execution works. Parallel support in progress |
| Internal procedure as an actual argument or pointer target | Y | Current implementation requires stack to be executable. See Proposal |
All features except those listed in the following table are supported.
| Feature | Status | Comments |
|---|---|---|
| Parameterized Derived Types | P | PDT with length type parameters is not supported. See Proposal |
| Assignment to allocatable | P | Assignment to whole allocatable in FORALL is not implemented |
| Asynchronous input/output | P | IO will happen synchronously |
| MIN/MAX extensions for CHARACTER | P | Some variants are not supported |
All features are supported.
All features are supported.
All features are supported.