re PR fortran/34952 (Document lack of support for ENCODE/DECODE)
PR fortran/34952 * gfortran.texi: Create new section for unimplemented extensions. Add "STRUCTURE and RECORD" and "ENCODE and DECODE statements". Remove "smaller projects" list. Fix a few typos. From-SVN: r132366
This commit is contained in:
Francois-Xavier Coudert
François-Xavier Coudert
parent
a6ab737796
commit
49309826a0
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@ -1,3 +1,10 @@
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2008-02-16 Francois-Xavier Coudert <fxcoudert@gcc.gnu.org>
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PR fortran/34952
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* gfortran.texi: Create new section for unimplemented extensions.
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Add "STRUCTURE and RECORD" and "ENCODE and DECODE statements".
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Remove "smaller projects" list. Fix a few typos.
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2008-02-15 Francois-Xavier Coudert <fxcoudert@gcc.gnu.org>
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* intrinsic.texi: Rename INDEX node to avoid clashing with
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@ -613,8 +613,7 @@ the first letter is @samp{n}, @samp{N} or @samp{0}, I/O is buffered.
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This is the default.
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@node GFORTRAN_UNBUFFERED_PRECONNECTED
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@section @env{GFORTRAN_UNBUFFERED_PRECONNECTED}---Don't buffer I/O on
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preconnected units
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@section @env{GFORTRAN_UNBUFFERED_PRECONNECTED}---Don't buffer I/O on preconnected units
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The environment variable named @env{GFORTRAN_UNBUFFERED_PRECONNECTED} controls
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whether I/O on a preconnected unit (i.e STDOUT or STDERR) is unbuffered. If
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@ -877,7 +876,24 @@ BOZ as argument of INT, REAL, DBLE and CMPLX.
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@node Extensions
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@chapter Extensions
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@cindex Extension
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@cindex extensions
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The two sections below detail the extensions to standard Fortran that are
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implemented in GNU Fortran, as well as some of the popular or
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historically important extensions that are not (or not yet) implemented.
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For the latter case, we explain the alternatives available to GNU Fortran
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users, including replacement by standard-conforming code or GNU
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extensions.
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@menu
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* Extensions implemented in GNU Fortran::
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* Extensions not implemented in GNU Fortran::
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@end menu
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@node Extensions implemented in GNU Fortran
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@section Extensions implemented in GNU Fortran
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@cindex extensions, implemented
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GNU Fortran implements a number of extensions over standard
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Fortran. This chapter contains information on their syntax and
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@ -910,7 +926,7 @@ of extensions, and @option{-std=legacy} allows both without warning.
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@end menu
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@node Old-style kind specifications
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@section Old-style kind specifications
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@subsection Old-style kind specifications
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@cindex kind, old-style
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GNU Fortran allows old-style kind specifications in declarations. These
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@ -934,7 +950,7 @@ where @code{k} is equal to @code{size} for most types, but is equal to
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@code{size/2} for the @code{COMPLEX} type.
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@node Old-style variable initialization
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@section Old-style variable initialization
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@subsection Old-style variable initialization
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GNU Fortran allows old-style initialization of variables of the
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form:
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@ -968,7 +984,7 @@ or in @code{DATA} statements automatically acquire the @code{SAVE}
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attribute.
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@node Extensions to namelist
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@section Extensions to namelist
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@subsection Extensions to namelist
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@cindex Namelist
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GNU Fortran fully supports the Fortran 95 standard for namelist I/O
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@ -1037,7 +1053,7 @@ elements will be given the values 1.00 and 2.00.
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@end smallexample
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@node X format descriptor without count field
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@section @code{X} format descriptor without count field
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@subsection @code{X} format descriptor without count field
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To support legacy codes, GNU Fortran permits the count field of the
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@code{X} edit descriptor in @code{FORMAT} statements to be omitted.
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@ -1049,7 +1065,7 @@ When omitted, the count is implicitly assumed to be one.
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@end smallexample
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@node Commas in FORMAT specifications
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@section Commas in @code{FORMAT} specifications
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@subsection Commas in @code{FORMAT} specifications
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To support legacy codes, GNU Fortran allows the comma separator
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to be omitted immediately before and after character string edit
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@ -1062,7 +1078,7 @@ descriptors in @code{FORMAT} statements.
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@node Missing period in FORMAT specifications
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@section Missing period in @code{FORMAT} specifications
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@subsection Missing period in @code{FORMAT} specifications
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To support legacy codes, GNU Fortran allows missing periods in format
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specifications if and only if @option{-std=legacy} is given on the
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@ -1076,7 +1092,7 @@ discouraged.
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@end smallexample
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@node I/O item lists
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@section I/O item lists
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@subsection I/O item lists
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@cindex I/O item lists
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To support legacy codes, GNU Fortran allows the input item list
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@ -1084,7 +1100,7 @@ of the @code{READ} statement, and the output item lists of the
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@code{WRITE} and @code{PRINT} statements, to start with a comma.
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@node BOZ literal constants
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@section BOZ literal constants
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@subsection BOZ literal constants
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@cindex BOZ literal constants
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Besides decimal constants, Fortran also supports binary (@code{b}),
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@ -1133,14 +1149,14 @@ option can be used as a workaround for legacy code that initializes
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integers in this manner.
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@node Real array indices
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@section Real array indices
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@subsection Real array indices
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@cindex array, indices of type real
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As an extension, GNU Fortran allows the use of @code{REAL} expressions
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or variables as array indices.
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@node Unary operators
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@section Unary operators
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@subsection Unary operators
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@cindex operators, unary
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As an extension, GNU Fortran allows unary plus and unary minus operators
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@ -1152,7 +1168,7 @@ the need for parenthesis.
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@end smallexample
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@node Implicitly convert LOGICAL and INTEGER values
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@section Implicitly convert @code{LOGICAL} and @code{INTEGER} values
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@subsection Implicitly convert @code{LOGICAL} and @code{INTEGER} values
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@cindex conversion, to integer
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@cindex conversion, to logical
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@ -1178,7 +1194,7 @@ However, there is no implicit conversion of @code{INTEGER} values in
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in I/O operations.
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@node Hollerith constants support
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@section Hollerith constants support
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@subsection Hollerith constants support
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@cindex Hollerith constants
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GNU Fortran supports Hollerith constants in assignments, function
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@ -1220,8 +1236,8 @@ obtained by using the @code{TRANSFER} statement, as in this example.
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@node Cray pointers
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@section Cray pointers
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@cindex pointer, cray
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@subsection Cray pointers
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@cindex pointer, Cray
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Cray pointers are part of a non-standard extension that provides a
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C-like pointer in Fortran. This is accomplished through a pair of
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@ -1348,8 +1364,8 @@ variables in the invoked function. Subsequent changes to the pointer
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will not change the base address of the array that was passed.
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@node CONVERT specifier
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@section CONVERT specifier
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@cindex CONVERT specifier
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@subsection @code{CONVERT} specifier
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@cindex @code{CONVERT} specifier
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GNU Fortran allows the conversion of unformatted data between little-
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and big-endian representation to facilitate moving of data
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@ -1397,7 +1413,7 @@ to you, it is best if you use this only for data that needs to be
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portable.
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@node OpenMP
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@section OpenMP
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@subsection OpenMP
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@cindex OpenMP
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OpenMP (Open Multi-Processing) is an application programming
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@ -1456,11 +1472,11 @@ thus not recommended.
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@end itemize
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@node Argument list functions
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@section Argument list functions %VAL, %REF and %LOC
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@subsection Argument list functions @code{%VAL}, @code{%REF} and @code{%LOC}
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@cindex argument list functions
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@cindex %VAL
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@cindex %REF
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@cindex %LOC
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@cindex @code{%VAL}
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@cindex @code{%REF}
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@cindex @code{%LOC}
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GNU Fortran supports argument list functions @code{%VAL}, @code{%REF}
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and @code{%LOC} statements, for backward compatibility with g77.
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@ -1496,6 +1512,168 @@ For details refer to the g77 manual
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Also, the gfortran testsuite c_by_val.f and its partner c_by_val.c are
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worth a look.
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@node Extensions not implemented in GNU Fortran
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@section Extensions not implemented in GNU Fortran
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@cindex extensions, not implemented
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The long history of the Fortran language, its wide use and broad
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userbase, the large number of different compiler vendors and the lack of
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some features crucial to users in the first standards have lead to the
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existence of an important number of extensions to the language. While
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some of the most useful or popular extensions are supported by the GNU
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Fortran compiler, not all existing extensions are supported. This section
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aims at listing these extensions and offering advice on how best make
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code that uses them running with the GNU Fortran compiler.
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@c More can be found here:
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@c -- http://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/Missing-Features.html
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@c -- the list of fortran and libgfortran bugs closed as WONTFIX:
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@c http://tinyurl.com/2u4h5y
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@menu
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* STRUCTURE and RECORD::
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@c * UNION and MAP::
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* ENCODE and DECODE statements::
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@c * Expressions in FORMAT statements::
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@c * Q edit descriptor::
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@c * AUTOMATIC statement::
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@c * TYPE and ACCEPT I/O Statements::
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@c * .XOR. operator::
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@c * CARRIAGECONTROL, DEFAULTFILE, DISPOSE and RECORDTYPE I/O specifiers::
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@c * Omitted arguments in procedure call:
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@end menu
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@node STRUCTURE and RECORD
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@subsection @code{STRUCTURE} and @code{RECORD}
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@cindex @code{STRUCTURE}
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@cindex @code{RECORD}
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Structures are user-defined aggregate data types; this functionality was
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standardized in Fortran 90 with an different syntax, under the name of
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``derived types''. Here is an example of code using the non portable
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structure syntax:
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@example
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! Declaring a structure named ``item'' and containing three fields:
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! an integer ID, an description string and a floating-point price.
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STRUCTURE /item/
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INTEGER id
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CHARACTER(LEN=200) description
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REAL price
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END STRUCTURE
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! Define two variables, an single record of type ``item''
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! named ``pear'', and an array of items named ``store_catalog''
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RECORD /item/ pear, store_catalog(100)
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! We can directly access the fields of both variables
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pear.id = 92316
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pear.description = "juicy D'Anjou pear"
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pear.price = 0.15
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store_catalog(7).id = 7831
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store_catalog(7).description = "milk bottle"
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store_catalog(7).price = 1.2
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! We can also manipulates the whole structure
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store_catalog(12) = pear
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print *, store_catalog(12)
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@end example
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@noindent
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This code can easily be rewritten in the Fortran 90 syntax as following:
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@example
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! ``STRUCTURE /name/ ... END STRUCTURE'' becomes
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! ``TYPE name ... END TYPE''
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TYPE item
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INTEGER id
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CHARACTER(LEN=200) description
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REAL price
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END TYPE
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! ``RECORD /name/ variable'' becomes ``TYPE(name) variable''
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TYPE(item) pear, store_catalog(100)
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! Instead of using a dot (.) to access fields of a record, the
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! standard syntax uses a percent sign (%)
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pear%id = 92316
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pear%description = "juicy D'Anjou pear"
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pear%price = 0.15
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store_catalog(7)%id = 7831
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store_catalog(7)%description = "milk bottle"
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store_catalog(7)%price = 1.2
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! Assignments of a whole variable don't change
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store_catalog(12) = pear
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print *, store_catalog(12)
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@end example
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@c @node UNION and MAP
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@c @subsection @code{UNION} and @code{MAP}
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@c @cindex @code{UNION}
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@c @cindex @code{MAP}
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@c
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@c For help writing this one, see
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@c http://www.eng.umd.edu/~nsw/ench250/fortran1.htm#UNION and
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@c http://www.tacc.utexas.edu/services/userguides/pgi/pgiws_ug/pgi32u06.htm
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@node ENCODE and DECODE statements
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@subsection @code{ENCODE} and @code{DECODE} statements
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@cindex @code{ENCODE}
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@cindex @code{DECODE}
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GNU Fortran doesn't support the @code{ENCODE} and @code{DECODE}
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statements. These statements are best replaced by @code{READ} and
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@code{WRITE} statements involving internal files (@code{CHARACTER}
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variables and arrays), which have been part of the Fortran standard since
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Fortran 77. For example, replace a code fragment like
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@smallexample
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INTEGER*1 LINE(80)
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REAL A, B, C
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c ... Code that sets LINE
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DECODE (80, 9000, LINE) A, B, C
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9000 FORMAT (1X, 3(F10.5))
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@end smallexample
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@noindent
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with the following:
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@smallexample
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CHARACTER(LEN=80) LINE
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REAL A, B, C
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c ... Code that sets LINE
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READ (UNIT=LINE, FMT=9000) A, B, C
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9000 FORMAT (1X, 3(F10.5))
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@end smallexample
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Similarly, replace a code fragment like
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@smallexample
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INTEGER*1 LINE(80)
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REAL A, B, C
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c ... Code that sets A, B and C
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ENCODE (80, 9000, LINE) A, B, C
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9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
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@end smallexample
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@noindent
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with the following:
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@smallexample
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INTEGER*1 LINE(80)
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REAL A, B, C
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c ... Code that sets A, B and C
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WRITE (UNIT=LINE, FMT=9000) A, B, C
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9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
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@end smallexample
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@c ---------------------------------------------------------------------
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@c Intrinsic Procedures
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@c ---------------------------------------------------------------------
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@ -1594,7 +1772,7 @@ GNU Fortran project:
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@itemize @minus
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@item Bill Clodius
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@item Dominique d'Humieres
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@item Dominique d'Humi@`eres
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@item Kate Hedstrom
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@item Erik Schnetter
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@end itemize
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@ -1613,28 +1791,20 @@ list above, please contact us.
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@table @emph
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@item Help build the test suite
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Solicit more code for donation to the test suite.
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We can keep code private on request.
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Solicit more code for donation to the test suite: the more extensive the
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testsuite, the smaller the risk of breaking things in the future! We can
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keep code private on request.
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@item Bug hunting/squishing
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Find bugs and write more test cases!
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Test cases are especially very welcome,
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because it allows us to concentrate on fixing bugs
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instead of isolating them.
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Find bugs and write more test cases! Test cases are especially very
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welcome, because it allows us to concentrate on fixing bugs instead of
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isolating them. Going through the bugzilla database at
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@url{http://gcc.gnu.org/bugzilla/} to reduce testcases posted there and
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add more information (for example, for which version does the testcase
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work, for which versions does it fail?) is also very helpful.
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@item Smaller projects (``bug'' fixes):
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@itemize @minus
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@item Allow init exprs to be numbers raised to integer powers.
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@item Implement correct rounding.
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@item Implement F restrictions on Fortran 95 syntax.
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@item See about making Emacs-parsable error messages.
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@end itemize
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@end table
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If you wish to work on the runtime libraries,
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please contact a project maintainer.
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@c TODO: email!
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@node Proposed Extensions
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@section Proposed Extensions
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