diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/fortran/gfortran.texi | 67 | ||||
| -rw-r--r-- | gcc/fortran/invoke.texi | 5 |
2 files changed, 71 insertions, 1 deletions
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi index 7e8783a..f0cdbae 100644 --- a/gcc/fortran/gfortran.texi +++ b/gcc/fortran/gfortran.texi @@ -1192,6 +1192,7 @@ extensions. @menu * Extensions implemented in GNU Fortran:: * Extensions not implemented in GNU Fortran:: +* Experimental features for Fortran 202Y:: @end menu @@ -2701,7 +2702,73 @@ descriptor occurred, use @code{INQUIRE} to get the file position, count the characters up to the next @code{NEW_LINE} and then start reading from the position marked previously. +@node Experimental features for Fortran 202Y +@section Experimental features for Fortran 202Y +@cindex Fortran 202Y +GNU Fortran supports some experimental features which have been +proposed and accepted by the J3 standards committee. These +exist to give users a chance to try them out, and to provide +a reference implementation. + +As these features have not been finalized, there is a chance that the +version in the upcoming standard will differ from what GNU Fortran +currently implements. Stability of these implementations is therefore +not guaranteed. + +@menu +* Unsigned integers:: +@end menu + +@node Unsigned integers +@subsection Unsigned integers +@cindex Unsigned integers +GNU Fortran supports unsigned integers according to +@uref{https://j3-fortran.org/doc/year/24/24-116.txt, J3/24-116}. The +data type is called @code{UNSIGNED}. For an unsigned type with $n$ bits, +it implements integer arithmetic modulo @code{2**n}, comparable to the +@code{unsigned} data type in C. + +The data type has @code{KIND} numbers comparable to other Fortran data +types, which can be selected via the @code{SELECTED_UNSIGNED_KIND} +function. + +Mixed arithmetic, comparisoins and assignment between @code{UNSIGNED} +and other types are only possible via explicit conversion. Conversion +from @code{UNSIGNED} to other types is done via type conversion +functions like @code{INT} or @code{REAL}. Unsigned variables cannot be +used as index variables in @code{DO} loops or as array indices. + +Unsigned numbers have a trailing @code{u} as suffix, optionally followed +by a @code{KIND} number separated by an underscore. + +Input and output can be done using the @code{I} and (to be +implemented) @code{X}, @code{O} and @code{Z} descriptors, plus +unformatted I/O. + +Here is a small, somewhat contrived example of their use: +@smallexample +program main + unsigned(kind=8) :: v + v = huge(v) - 32u_8 + print *,v +end program main +@end smallexample +which will output the number 18446744073709551583. + +Generally, unsigned integers are only permitted as data in intrinsics, +not, for example, for counting bits. +As of now, the following intrinsics take unsigned arguments: +@itemize @bullet +@item @code{BLT}, @code{BLE}, @code{BGE} and @code{BGT}. These intrinsics + are actually redundante because comparison operators could be used + directly. +@item @code{IAND}, @code{IOR}, @code{IEOR} and @code{NOT} +@item @code{BIT_SIZE}, @code{DIGITS} and @code{HUGE} +@item @code{DSHIFTL} and @code{DSHIFTR} +@item @code{IBCLR}, @code{IBITS} and @code{IBITS} +@end itemize +This list will grow in the near future. @c --------------------------------------------------------------------- @c --------------------------------------------------------------------- @c Mixed-Language Programming diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi index 6bc42af..dcb5782 100644 --- a/gcc/fortran/invoke.texi +++ b/gcc/fortran/invoke.texi @@ -129,7 +129,7 @@ by type. Explanations are in the following sections. -fmodule-private -ffixed-form -fno-range-check -fopenacc -fopenmp -fopenmp-allocators -fopenmp-simd -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 -freal-8-real-10 -freal-8-real-16 -freal-8-real-4 --std=@var{std} -ftest-forall-temp +-std=@var{std} -ftest-forall-temp -funsigned } @item Preprocessing Options @@ -611,6 +611,9 @@ earlier gfortran versions and should not be used any more. @item -ftest-forall-temp Enhance test coverage by forcing most forall assignments to use temporary. +@opindex @code{funsigned} +@item -funsigned +Allow the experimental unsigned extension. @end table @node Preprocessing Options |