re PR fortran/54339 (Update gfortran manual for GCC 4.8's TS29113 changes)
2013-02-07 Tobias Burnus <burnus@net-b.de>
PR fortran/54339
* gfortran.texi (Standards): Mention TS29113.
(Varying Length Character): Mention deferred-length
strings.
(Fortran 2003 Status): Add unlimited polymorphic.
(TS 29113 Status): Add TYPE(*) and DIMENSION(..).
(C Interop): Update the section about TS29113.
From-SVN: r195845
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Tobias Burnus
Tobias Burnus
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@ -1,3 +1,13 @@
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2013-02-07 Tobias Burnus <burnus@net-b.de>
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PR fortran/54339
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* gfortran.texi (Standards): Mention TS29113.
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(Varying Length Character): Mention deferred-length
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strings.
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(Fortran 2003 Status): Add unlimited polymorphic.
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(TS 29113 Status): Add TYPE(*) and DIMENSION(..).
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(C Interop): Update the section about TS29113.
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2013-02-06 Paul Thomas <pault@gcc.gnu.org>
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PR fortran/55789
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@ -221,7 +221,7 @@ compiler.
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The GNU Fortran compiler front end was
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designed initially as a free replacement for,
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or alternative to, the unix @command{f95} command;
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or alternative to, the Unix @command{f95} command;
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@command{gfortran} is the command you will use to invoke the compiler.
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@menu
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@ -522,12 +522,13 @@ ISO/IEC 1539:1997 (Fortran 95). As such, it can also compile essentially all
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standard-compliant Fortran 90 and Fortran 77 programs. It also supports
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the ISO/IEC TR-15581 enhancements to allocatable arrays.
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In the future, the GNU Fortran compiler will also support ISO/IEC
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1539-1:2004 (Fortran 2003), ISO/IEC 1539-1:2010 (Fortran 2008) and
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future Fortran standards. Partial support of the Fortran 2003 and
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Fortran 2008 standard is already provided; the current status of the
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support is reported in the @ref{Fortran 2003 status} and
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@ref{Fortran 2008 status} sections of the documentation.
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GNU Fortran also have a partial support for ISO/IEC 1539-1:2004 (Fortran
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2003), ISO/IEC 1539-1:2010 (Fortran 2008), the Technical Specification
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@code{Further Interoperability of Fortran with C} (ISO/IEC TS 29113:2012).
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Full support of those standards and future Fortran standards is planned.
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The current status of the support is can be found in the
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@ref{Fortran 2003 status}, @ref{Fortran 2008 status} and
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@ref{TS 29113 status} sections of the documentation.
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Additionally, the GNU Fortran compilers supports the OpenMP specification
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(version 3.1, @url{http://openmp.org/@/wp/@/openmp-specifications/}).
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@ -545,6 +546,10 @@ for them, which work with GNU Fortran. They can be found at
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@uref{http://www.fortran.com/@/iso_varying_string.f95} and at
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@uref{ftp://ftp.nag.co.uk/@/sc22wg5/@/ISO_VARYING_STRING/}.
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Deferred-length character strings of Fortran 2003 supports part of
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the features of @code{ISO_VARYING_STRING} and should be considered as
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replacement. (Namely, allocatable or pointers of the type
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@code{character(len=:)}.)
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@c =====================================================================
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@ -807,8 +812,8 @@ operators bound to a type.
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override type-bound procedures or to have deferred binding.
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@item Polymorphic entities (``@code{CLASS}'') for derived types -- including
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@code{SAME_TYPE_AS}, @code{EXTENDS_TYPE_OF} and @code{SELECT TYPE}.
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Note that unlimited polymorphism is currently not supported.
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@code{SAME_TYPE_AS}, @code{EXTENDS_TYPE_OF} and @code{SELECT TYPE} for
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scalars and arrays, including unlimited polymorphism.
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@item Generic interface names, which have the same name as derived types,
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are now supported. This allows one to write constructor functions. Note
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@ -1079,16 +1084,23 @@ The @uref{http://gcc.gnu.org/wiki/TS29113Status, wiki} has some information
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about the current TS 29113 implementation status. In particular, the
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following is implemented.
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See also @ref{Further Interoperability of Fortran with C}.
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@itemize
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@item The @option{-std=f2008ts} option.
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@item The @code{OPTIONAL} attribute is allowed for dummy arguments
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of @code{BIND(C) procedures.}
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@item The RANK intrinsic is supported.
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@item The @code{RANK} intrinsic is supported.
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@item GNU Fortran's implementation for variables with @code{ASYNCHRONOUS}
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attribute is compatible with TS 29113.
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@item Assumed types (@code{TYPE(*)}.
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@item Assumed-rank (@code{DIMENSION(..)}). However, the array descriptor
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of the TS is not yet supported.
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@end itemize
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@ -2264,7 +2276,7 @@ Derived types with the C binding attribute shall not have the @code{sequence}
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attribute, type parameters, the @code{extends} attribute, nor type-bound
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procedures. Every component must be of interoperable type and kind and may not
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have the @code{pointer} or @code{allocatable} attribute. The names of the
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variables are irrelevant for interoperability.
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components are irrelevant for interoperability.
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As there exist no direct Fortran equivalents, neither unions nor structs
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with bit field or variable-length array members are interoperable.
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@ -2304,11 +2316,14 @@ be compatible with C. The dummy argument declaration is relatively
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straightforward. However, one needs to be careful because C uses
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call-by-value by default while Fortran behaves usually similar to
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call-by-reference. Furthermore, strings and pointers are handled
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differently. Note that only explicit size and assumed-size arrays are
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supported but not assumed-shape or allocatable arrays.
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differently. Note that in Fortran 2003 and 2008 only explicit size
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and assumed-size arrays are supported but not assumed-shape or
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deferred-shape (i.e. allocatable or pointer) arrays. However, those
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are allowed since the Technical Specification 29113, see
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@ref{Further Interoperability of Fortran with C}
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To pass a variable by value, use the @code{VALUE} attribute.
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Thus the following C prototype
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Thus, the following C prototype
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@smallexample
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@code{int func(int i, int *j)}
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@ -2401,6 +2416,11 @@ The intrinsic procedures are described in @ref{Intrinsic Procedures}.
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C pointers are represented in Fortran via the special opaque derived type
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@code{type(c_ptr)} (with private components). Thus one needs to
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use intrinsic conversion procedures to convert from or to C pointers.
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For some applications, using an assumed type (@code{TYPE(*)}) can be an
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alternative to a C pointer; see
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@ref{Further Interoperability of Fortran with C}.
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For example,
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@smallexample
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@ -2546,17 +2566,76 @@ END MODULE m
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@node Further Interoperability of Fortran with C
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@subsection Further Interoperability of Fortran with C
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Assumed-shape and allocatable arrays are passed using an array descriptor
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(dope vector). The internal structure of the array descriptor used
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by GNU Fortran is not yet documented and will change. There will also be
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a Technical Specification (TS 29113) which standardizes an interoperable
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array descriptor. Until then, you can use the Chasm Language
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The Technical Specification ISO/IEC TS 29113:2012 on further
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interoperability of Fortran with C extends the interoperability support
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of Fortran 2003 and Fortran 2008. Besides removing some restrictions
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and constraints, it adds assumed-type (@code{TYPE(*)}) and assumed-rank
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(@code{dimension}) variables and allows for interoperability of
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assumed-shape, assumed-rank and deferred-shape arrays, including
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allocatables and pointers.
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Note: Currently, GNU Fortran does not support the array descriptor
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(dope vector) as specified in the Technical Specification, but uses
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an array descriptor with different fields. The Chasm Language
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Interoperability Tools, @url{http://chasm-interop.sourceforge.net/},
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which provide an interface to GNU Fortran's array descriptor.
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provide an interface to GNU Fortran's array descriptor.
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GNU Fortran already supports the C-interoperable @code{OPTIONAL}
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attribute; for absent arguments, a @code{NULL} pointer is passed.
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The Technical Specification adds the following new features, which
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are supported by GNU Fortran:
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@itemize @bullet
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@item The @code{ASYNCHRONOUS} attribute has been clarified and
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extended to allow its use with asynchronous communication in
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user-provided libraries such as in implementations of the
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Message Passing Interface specification.
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@item Many constraints have been relaxed, in particular for
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the @code{C_LOC} and @code{C_F_POINTER} intrinsics.
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@item The @code{OPTIONAL} attribute is now allowed for dummy
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arguments; an absent argument matches a @code{NULL} pointer.
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@item Assumed types (@code{TYPE(*)}) have been added, which may
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only be used for dummy arguments. They are unlimited polymorphic
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but contrary to @code{CLASS(*)} they do not contain any type
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information, similar to C's @code{void *} pointers. Expressions
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of any type and kind can be passed; thus, it can be used as
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replacement for @code{TYPE(C_PTR)}, avoiding the use of
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@code{C_LOC} in the caller.
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Note, however, that @code{TYPE(*)} only accepts scalar arguments,
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unless the @code{DIMENSION} is explicitly specified. As
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@code{DIMENSION(*)} only supports array (including array elements) but
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no scalars, it is not a full replacement for @code{C_LOC}. On the
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other hand, assumed-type assumed-rank dummy arguments
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(@code{TYPE(*), DIMENSION(..)}) allow for both scalars and arrays, but
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require special code on the callee side to handle the array descriptor.
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@item Assumed-shape arrays (@code{DIMENSION(..)}) as dummy argument
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allow that scalars and arrays of any rank can be passed as actual
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argument. As the Technical Specification does not provide for direct
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means to operate with them, they have to be used either from the C side
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or be converted using @code{C_LOC} and @code{C_F_POINTER} to scalars
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or arrays of a specific rank. The rank can be determined using the
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@code{RANK} intrinisic.
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@end itemize
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Currently unimplemented:
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@itemize @bullet
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@item GNU Fortran always uses an array descriptor, which does not
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match the one of the Technical Specification. The
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@code{ISO_Fortran_binding.h} header file and the C functions it
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specifies are not available.
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@item Using assumed-shape, assumed-rank and deferred-shape arrays in
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@code{BIND(C)} procedures is not fully supported. In particular,
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C interoperable strings of other length than one are not supported
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as this requires the new array descriptor.
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@end itemize
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@node GNU Fortran Compiler Directives
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@ -3100,7 +3179,7 @@ Environment variable for filename for * IO-unit.
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Environment variable for temporary file directory.
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@item
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Environment variable forcing standard output to be line buffered (unix).
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Environment variable forcing standard output to be line buffered (Unix).
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@end itemize
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