1 \input texinfo @c -*-texinfo-*-
3 @setfilename gfortran.info
4 @set copyrights-gfortran 1999-2007
6 @include gcc-common.texi
8 @settitle The GNU Fortran Compiler
10 @c Create a separate index for command line options
12 @c Merge the standard indexes into a single one.
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20 @c until they are incorporated into the official Texinfo distribution.
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60 @c Use with @@smallbook.
62 @c %** start of document
64 @c Cause even numbered pages to be printed on the left hand side of
65 @c the page and odd numbered pages to be printed on the right hand
66 @c side of the page. Using this, you can print on both sides of a
67 @c sheet of paper and have the text on the same part of the sheet.
69 @c The text on right hand pages is pushed towards the right hand
70 @c margin and the text on left hand pages is pushed toward the left
72 @c (To provide the reverse effect, set bindingoffset to -0.75in.)
75 @c \global\bindingoffset=0.75in
76 @c \global\normaloffset =0.75in
80 Copyright @copyright{} @value{copyrights-gfortran} Free Software Foundation, Inc.
82 Permission is granted to copy, distribute and/or modify this document
83 under the terms of the GNU Free Documentation License, Version 1.1 or
84 any later version published by the Free Software Foundation; with the
85 Invariant Sections being ``GNU General Public License'' and ``Funding
86 Free Software'', the Front-Cover
87 texts being (a) (see below), and with the Back-Cover Texts being (b)
88 (see below). A copy of the license is included in the section entitled
89 ``GNU Free Documentation License''.
91 (a) The FSF's Front-Cover Text is:
95 (b) The FSF's Back-Cover Text is:
97 You have freedom to copy and modify this GNU Manual, like GNU
98 software. Copies published by the Free Software Foundation raise
99 funds for GNU development.
103 @dircategory Software development
105 * gfortran: (gfortran). The GNU Fortran Compiler.
107 This file documents the use and the internals of
108 the GNU Fortran compiler, (@command{gfortran}).
110 Published by the Free Software Foundation
111 51 Franklin Street, Fifth Floor
112 Boston, MA 02110-1301 USA
118 @setchapternewpage odd
120 @title Using GNU Fortran
122 @author The @t{gfortran} team
124 @vskip 0pt plus 1filll
125 Published by the Free Software Foundation@*
126 51 Franklin Street, Fifth Floor@*
127 Boston, MA 02110-1301, USA@*
128 @c Last printed ??ber, 19??.@*
129 @c Printed copies are available for $? each.@*
135 @c TODO: The following "Part" definitions are included here temporarily
136 @c until they are incorporated into the official Texinfo distribution.
139 \global\let\partentry=\dosmallpartentry
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152 @c ---------------------------------------------------------------------
153 @c TexInfo table of contents.
154 @c ---------------------------------------------------------------------
161 This manual documents the use of @command{gfortran},
162 the GNU Fortran compiler. You can find in this manual how to invoke
163 @command{gfortran}, as well as its features and incompatibilities.
166 @emph{Warning:} This document, and the compiler it describes, are still
167 under development. While efforts are made to keep it up-to-date, it might
168 not accurately reflect the status of the most recent GNU Fortran compiler.
172 @comment When you add a new menu item, please keep the right hand
173 @comment aligned to the same column. Do not use tabs. This provides
174 @comment better formatting.
179 Part I: Invoking GNU Fortran
180 * Invoking GNU Fortran:: Command options supported by @command{gfortran}.
181 * Runtime:: Influencing runtime behavior with environment variables.
183 Part II: Language Reference
184 * Fortran 2003 status:: Fortran 2003 features supported by GNU Fortran.
185 * Extensions:: Language extensions implemented by GNU Fortran.
186 * Intrinsic Procedures:: Intrinsic procedures supported by GNU Fortran.
188 * Contributing:: How you can help.
189 * Copying:: GNU General Public License says
190 how you can copy and share GNU Fortran.
191 * GNU Free Documentation License::
192 How you can copy and share this manual.
193 * Funding:: How to help assure continued work for free software.
194 * Option Index:: Index of command line options
195 * Keyword Index:: Index of concepts
199 @c ---------------------------------------------------------------------
201 @c ---------------------------------------------------------------------
204 @chapter Introduction
206 @c The following duplicates the text on the TexInfo table of contents.
208 This manual documents the use of @command{gfortran}, the GNU Fortran
209 compiler. You can find in this manual how to invoke @command{gfortran},
210 as well as its features and incompatibilities.
213 @emph{Warning:} This document, and the compiler it describes, are still
214 under development. While efforts are made to keep it up-to-date, it
215 might not accurately reflect the status of the most recent GNU Fortran
220 The GNU Fortran compiler front end was
221 designed initially as a free replacement for,
222 or alternative to, the unix @command{f95} command;
223 @command{gfortran} is the command you'll use to invoke the compiler.
226 * About GNU Fortran:: What you should know about the GNU Fortran compiler.
227 * GNU Fortran and GCC:: You can compile Fortran, C, or other programs.
228 * GNU Fortran and G77:: Why we chose to start from scratch.
229 * Project Status:: Status of GNU Fortran, roadmap, proposed extensions.
230 * Standards:: Standards supported by GNU Fortran.
234 @c ---------------------------------------------------------------------
236 @c ---------------------------------------------------------------------
238 @node About GNU Fortran
239 @section About GNU Fortran
241 The GNU Fortran compiler is still in an early state of development.
242 It can generate code for most constructs and expressions,
243 but much work remains to be done.
245 When the GNU Fortran compiler is finished,
246 it will do everything you expect from any decent compiler:
250 Read a user's program,
251 stored in a file and containing instructions written
252 in Fortran 77, Fortran 90, Fortran 95 or Fortran 2003.
253 This file contains @dfn{source code}.
256 Translate the user's program into instructions a computer
257 can carry out more quickly than it takes to translate the
258 instructions in the first
259 place. The result after compilation of a program is
261 code designed to be efficiently translated and processed
262 by a machine such as your computer.
263 Humans usually aren't as good writing machine code
264 as they are at writing Fortran (or C++, Ada, or Java),
265 because is easy to make tiny mistakes writing machine code.
268 Provide the user with information about the reasons why
269 the compiler is unable to create a binary from the source code.
270 Usually this will be the case if the source code is flawed.
271 When writing Fortran, it is easy to make big mistakes.
272 The Fortran 90 requires that the compiler can point out
273 mistakes to the user.
274 An incorrect usage of the language causes an @dfn{error message}.
276 The compiler will also attempt to diagnose cases where the
277 user's program contains a correct usage of the language,
278 but instructs the computer to do something questionable.
279 This kind of diagnostics message is called a @dfn{warning message}.
282 Provide optional information about the translation passes
283 from the source code to machine code.
284 This can help a user of the compiler to find the cause of
285 certain bugs which may not be obvious in the source code,
286 but may be more easily found at a lower level compiler output.
287 It also helps developers to find bugs in the compiler itself.
290 Provide information in the generated machine code that can
291 make it easier to find bugs in the program (using a debugging tool,
292 called a @dfn{debugger}, such as the GNU Debugger @command{gdb}).
295 Locate and gather machine code already generated to
296 perform actions requested by statements in the user's program.
297 This machine code is organized into @dfn{modules} and is located
298 and @dfn{linked} to the user program.
301 The GNU Fortran compiler consists of several components:
305 A version of the @command{gcc} command
306 (which also might be installed as the system's @command{cc} command)
307 that also understands and accepts Fortran source code.
308 The @command{gcc} command is the @dfn{driver} program for
309 all the languages in the GNU Compiler Collection (GCC);
311 you can compile the source code of any language for
312 which a front end is available in GCC.
315 The @command{gfortran} command itself,
316 which also might be installed as the
317 system's @command{f95} command.
318 @command{gfortran} is just another driver program,
319 but specifically for the Fortran compiler only.
320 The difference with @command{gcc} is that @command{gfortran}
321 will automatically link the correct libraries to your program.
324 A collection of run-time libraries.
325 These libraries contain the machine code needed to support
326 capabilities of the Fortran language that are not directly
327 provided by the machine code generated by the
328 @command{gfortran} compilation phase,
329 such as intrinsic functions and subroutines,
330 and routines for interaction with files and the operating system.
331 @c and mechanisms to spawn,
332 @c unleash and pause threads in parallelized code.
335 The Fortran compiler itself, (@command{f951}).
336 This is the GNU Fortran parser and code generator,
337 linked to and interfaced with the GCC backend library.
338 @command{f951} ``translates'' the source code to
339 assembler code. You would typically not use this
341 instead, the @command{gcc} or @command{gfortran} driver
342 programs will call it for you.
346 @c ---------------------------------------------------------------------
347 @c GNU Fortran and GCC
348 @c ---------------------------------------------------------------------
350 @node GNU Fortran and GCC
351 @section GNU Fortran and GCC
352 @cindex GNU Compiler Collection
355 GNU Fortran is a part of GCC, the @dfn{GNU Compiler Collection}. GCC
356 consists of a collection of front ends for various languages, which
357 translate the source code into a language-independent form called
358 @dfn{GENERIC}. This is then processed by a common middle end which
359 provides optimization, and then passed to one of a collection of back
360 ends which generate code for different computer architectures and
363 Functionally, this is implemented with a driver program (@command{gcc})
364 which provides the command-line interface for the compiler. It calls
365 the relevant compiler front-end program (e.g., @command{f951} for
366 Fortran) for each file in the source code, and then calls the assembler
367 and linker as appropriate to produce the compiled output. In a copy of
368 GCC which has been compiled with Fortran language support enabled,
369 @command{gcc} will recognize files with @file{.f}, @file{.f90}, @file{.f95},
370 and @file{.f03} extensions as Fortran source code, and compile it
371 accordingly. A @command{gfortran} driver program is also provided,
372 which is identical to @command{gcc} except that it automatically links
373 the Fortran runtime libraries into the compiled program.
375 This manual specifically documents the Fortran front end, which handles
376 the programming language's syntax and semantics. The aspects of GCC
377 which relate to the optimization passes and the back-end code generation
378 are documented in the GCC manual; see
379 @ref{Top,,Introduction,gcc,Using the GNU Compiler Collection (GCC)}.
380 The two manuals together provide a complete reference for the GNU
384 @c ---------------------------------------------------------------------
385 @c GNU Fortran and G77
386 @c ---------------------------------------------------------------------
388 @node GNU Fortran and G77
389 @section GNU Fortran and G77
391 @cindex @command{g77}
393 The GNU Fortran compiler is the successor to @command{g77}, the Fortran
394 77 front end included in GCC prior to version 4. It is an entirely new
395 program that has been designed to provide Fortran 95 support and
396 extensibility for future Fortran language standards, as well as providing
397 backwards compatibility for Fortran 77 and nearly all of the GNU language
398 extensions supported by @command{g77}.
401 @c ---------------------------------------------------------------------
403 @c ---------------------------------------------------------------------
406 @section Project Status
409 As soon as @command{gfortran} can parse all of the statements correctly,
410 it will be in the ``larva'' state.
411 When we generate code, the ``puppa'' state.
412 When @command{gfortran} is done,
413 we'll see if it will be a beautiful butterfly,
414 or just a big bug....
416 --Andy Vaught, April 2000
419 The start of the GNU Fortran 95 project was announced on
420 the GCC homepage in March 18, 2000
421 (even though Andy had already been working on it for a while,
424 The GNU Fortran compiler is able to compile nearly all
425 standard-compliant Fortran 95, Fortran 90, and Fortran 77 programs,
426 including a number of standard and non-standard extensions, and can be
427 used on real-world programs. In particular, the supported extensions
428 include OpenMP, Cray-style pointers, and several Fortran 2003 features
429 such as enumeration, stream I/O, and some of the enhancements to
430 allocatable array support from TR 15581. However, it is still under
431 development and has a few remaining rough edges.
433 At present, the GNU Fortran compiler passes the
434 @uref{http://www.fortran-2000.com/ArnaudRecipes/fcvs21_f95.html,
435 NIST Fortran 77 Test Suite}, and produces acceptable results on the
436 @uref{http://www.netlib.org/lapack/faq.html#1.21, LAPACK Test Suite}.
437 It also provides respectable performance on
438 the @uref{http://www.polyhedron.com/pb05.html, Polyhedron Fortran
439 compiler benchmarks} and the
440 @uref{http://www.llnl.gov/asci_benchmarks/asci/limited/lfk/README.html,
441 Livermore Fortran Kernels test}. It has been used to compile a number of
442 large real-world programs, including
443 @uref{http://mysite.verizon.net/serveall/moene.pdf, the HIRLAM
444 weather-forecasting code} and
445 @uref{http://www.theochem.uwa.edu.au/tonto/, the Tonto quantum
446 chemistry package}; see @url{http://gcc.gnu.org/wiki/GfortranApps} for an
449 Among other things, the GNU Fortran compiler is intended as a replacement
450 for G77. At this point, nearly all programs that could be compiled with
451 G77 can be compiled with GNU Fortran, although there are a few minor known
454 The primary work remaining to be done on GNU Fortran falls into three
455 categories: bug fixing (primarily regarding the treatment of invalid code
456 and providing useful error messages), improving the compiler optimizations
457 and the performance of compiled code, and extending the compiler to support
458 future standards---in particular, Fortran 2003.
461 @c ---------------------------------------------------------------------
463 @c ---------------------------------------------------------------------
469 The GNU Fortran compiler implements
470 ISO/IEC 1539:1997 (Fortran 95). As such, it can also compile essentially all
471 standard-compliant Fortran 90 and Fortran 77 programs. It also supports
472 the ISO/IEC TR-15581 enhancements to allocatable arrays, and
473 the @uref{http://www.openmp.org/drupal/mp-documents/spec25.pdf,
474 OpenMP Application Program Interface v2.5} specification.
476 In the future, the GNU Fortran compiler may also support other standard
477 variants of and extensions to the Fortran language. These include
478 ISO/IEC 1539-1:2004 (Fortran 2003).
481 @c =====================================================================
482 @c PART I: INVOCATION REFERENCE
483 @c =====================================================================
486 \part{I}{Invoking GNU Fortran}
489 @c ---------------------------------------------------------------------
491 @c ---------------------------------------------------------------------
496 @c ---------------------------------------------------------------------
498 @c ---------------------------------------------------------------------
501 @chapter Runtime: Influencing runtime behavior with environment variables
502 @cindex environment variable
504 The behavior of the @command{gfortran} can be influenced by
505 environment variables.
507 Malformed environment variables are silently ignored.
510 * GFORTRAN_STDIN_UNIT:: Unit number for standard input
511 * GFORTRAN_STDOUT_UNIT:: Unit number for standard output
512 * GFORTRAN_STDERR_UNIT:: Unit number for standard error
513 * GFORTRAN_USE_STDERR:: Send library output to standard error
514 * GFORTRAN_TMPDIR:: Directory for scratch files
515 * GFORTRAN_UNBUFFERED_n:: Don't buffer I/O for specific unit.
516 * GFORTRAN_UNBUFFERED_ALL:: Don't buffer I/O for all units.
517 * GFORTRAN_SHOW_LOCUS:: Show location for runtime errors
518 * GFORTRAN_OPTIONAL_PLUS:: Print leading + where permitted
519 * GFORTRAN_DEFAULT_RECL:: Default record length for new files
520 * GFORTRAN_LIST_SEPARATOR:: Separator for list output
521 * GFORTRAN_CONVERT_UNIT:: Set endianness for unformatted I/O
522 * GFORTRAN_ERROR_DUMPCORE:: Dump core on run-time errors
523 * GFORTRAN_ERROR_BACKTRACE:: Show backtrace on run-time errors
526 @node GFORTRAN_STDIN_UNIT
527 @section @env{GFORTRAN_STDIN_UNIT}---Unit number for standard input
529 This environment variable can be used to select the unit number
530 preconnected to standard input. This must be a positive integer.
531 The default value is 5.
533 @node GFORTRAN_STDOUT_UNIT
534 @section @env{GFORTRAN_STDOUT_UNIT}---Unit number for standard output
536 This environment variable can be used to select the unit number
537 preconnected to standard output. This must be a positive integer.
538 The default value is 6.
540 @node GFORTRAN_STDERR_UNIT
541 @section @env{GFORTRAN_STDERR_UNIT}---Unit number for standard error
543 This environment variable can be used to select the unit number
544 preconnected to standard error. This must be a positive integer.
545 The default value is 0.
547 @node GFORTRAN_USE_STDERR
548 @section @env{GFORTRAN_USE_STDERR}---Send library output to standard error
550 This environment variable controls where library output is sent.
551 If the first letter is @samp{y}, @samp{Y} or @samp{1}, standard
552 error is used. If the first letter is @samp{n}, @samp{N} or
553 @samp{0}, standard output is used.
555 @node GFORTRAN_TMPDIR
556 @section @env{GFORTRAN_TMPDIR}---Directory for scratch files
558 This environment variable controls where scratch files are
559 created. If this environment variable is missing,
560 GNU Fortran searches for the environment variable @env{TMP}. If
561 this is also missing, the default is @file{/tmp}.
563 @node GFORTRAN_UNBUFFERED_n
564 @section @env{GFORTRAN_UNBUFFERED_n}---Don't buffer I/O on unit n
566 Environment variables named @env{GFORTRAN_UNBUFFERED_n}, where
567 @samp{n} is an integer, control whether I/O on unit @samp{n} is
568 unbuffered. If the first letter is @samp{y}, @samp{Y} or @samp{1},
569 I/O is unbuffered. This will slow down small sequential reads and
570 writes. If the first letter is @samp{n}, @samp{N} or @samp{0}, I/O is
571 buffered. This is the default.
573 @node GFORTRAN_UNBUFFERED_ALL
574 @section @env{GFORTRAN_UNBUFFERED_ALL}---Don't buffer I/O on all units
576 This environment variable controls whether all I/O is unbuffered. If
577 the first letter is @samp{y}, @samp{Y} or @samp{1}, all I/O is
578 unbuffered. This will slow down small sequential reads and writes. If
579 the first letter is @samp{n}, @samp{N} or @samp{0}, I/O is buffered.
582 @node GFORTRAN_SHOW_LOCUS
583 @section @env{GFORTRAN_SHOW_LOCUS}---Show location for runtime errors
585 If the first letter is @samp{y}, @samp{Y} or @samp{1}, filename and
586 line numbers for runtime errors are printed. If the first letter is
587 @samp{n}, @samp{N} or @samp{0}, don't print filename and line numbers
588 for runtime errors. The default is to print the location.
590 @node GFORTRAN_OPTIONAL_PLUS
591 @section @env{GFORTRAN_OPTIONAL_PLUS}---Print leading + where permitted
593 If the first letter is @samp{y}, @samp{Y} or @samp{1},
594 a plus sign is printed
595 where permitted by the Fortran standard. If the first letter
596 is @samp{n}, @samp{N} or @samp{0}, a plus sign is not printed
597 in most cases. Default is not to print plus signs.
599 @node GFORTRAN_DEFAULT_RECL
600 @section @env{GFORTRAN_DEFAULT_RECL}---Default record length for new files
602 This environment variable specifies the default record length, in
603 bytes, for files which are opened without a @code{RECL} tag in the
604 @code{OPEN} statement. This must be a positive integer. The
605 default value is 1073741824 bytes (1 GB).
607 @node GFORTRAN_LIST_SEPARATOR
608 @section @env{GFORTRAN_LIST_SEPARATOR}---Separator for list output
610 This environment variable specifies the separator when writing
611 list-directed output. It may contain any number of spaces and
612 at most one comma. If you specify this on the command line,
613 be sure to quote spaces, as in
615 $ GFORTRAN_LIST_SEPARATOR=' , ' ./a.out
617 when @command{a.out} is the compiled Fortran program that you want to run.
618 Default is a single space.
620 @node GFORTRAN_CONVERT_UNIT
621 @section @env{GFORTRAN_CONVERT_UNIT}---Set endianness for unformatted I/O
623 By setting the @env{GFORTRAN_CONVERT_UNIT} variable, it is possible
624 to change the representation of data for unformatted files.
625 The syntax for the @env{GFORTRAN_CONVERT_UNIT} variable is:
627 GFORTRAN_CONVERT_UNIT: mode | mode ';' exception | exception ;
628 mode: 'native' | 'swap' | 'big_endian' | 'little_endian' ;
629 exception: mode ':' unit_list | unit_list ;
630 unit_list: unit_spec | unit_list unit_spec ;
631 unit_spec: INTEGER | INTEGER '-' INTEGER ;
633 The variable consists of an optional default mode, followed by
634 a list of optional exceptions, which are separated by semicolons
635 from the preceding default and each other. Each exception consists
636 of a format and a comma-separated list of units. Valid values for
637 the modes are the same as for the @code{CONVERT} specifier:
640 @item @code{NATIVE} Use the native format. This is the default.
641 @item @code{SWAP} Swap between little- and big-endian.
642 @item @code{LITTLE_ENDIAN} Use the little-endian format
643 for unformatted files.
644 @item @code{BIG_ENDIAN} Use the big-endian format for unformatted files.
646 A missing mode for an exception is taken to mean @code{BIG_ENDIAN}.
647 Examples of values for @env{GFORTRAN_CONVERT_UNIT} are:
649 @item @code{'big_endian'} Do all unformatted I/O in big_endian mode.
650 @item @code{'little_endian;native:10-20,25'} Do all unformatted I/O
651 in little_endian mode, except for units 10 to 20 and 25, which are in
653 @item @code{'10-20'} Units 10 to 20 are big-endian, the rest is native.
656 Setting the environment variables should be done on the command
657 line or via the @command{export}
658 command for @command{sh}-compatible shells and via @command{setenv}
659 for @command{csh}-compatible shells.
661 Example for @command{sh}:
664 $ GFORTRAN_CONVERT_UNIT='big_endian;native:10-20' ./a.out
667 Example code for @command{csh}:
670 % setenv GFORTRAN_CONVERT_UNIT 'big_endian;native:10-20'
674 Using anything but the native representation for unformatted data
675 carries a significant speed overhead. If speed in this area matters
676 to you, it is best if you use this only for data that needs to be
679 @xref{CONVERT specifier}, for an alternative way to specify the
680 data representation for unformatted files. @xref{Runtime Options}, for
681 setting a default data representation for the whole program. The
682 @code{CONVERT} specifier overrides the @option{-fconvert} compile options.
684 @emph{Note that the values specified via the GFORTRAN_CONVERT_UNIT
685 environment variable will override the CONVERT specifier in the
686 open statement}. This is to give control over data formats to
687 users who do not have the source code of their program available.
689 @node GFORTRAN_ERROR_DUMPCORE
690 @section @env{GFORTRAN_ERROR_DUMPCORE}---Dump core on run-time errors
692 If the @env{GFORTRAN_ERROR_DUMPCORE} variable is set to
693 @samp{y}, @samp{Y} or @samp{1} (only the first letter is relevant)
694 then library run-time errors cause core dumps. To disable the core
695 dumps, set the variable to @samp{n}, @samp{N}, @samp{0}. Default
696 is not to core dump unless the @option{-fdump-core} compile option
699 @node GFORTRAN_ERROR_BACKTRACE
700 @section @env{GFORTRAN_ERROR_BACKTRACE}---Show backtrace on run-time errors
702 If the @env{GFORTRAN_ERROR_BACKTRACE} variable is set to
703 @samp{y}, @samp{Y} or @samp{1} (only the first letter is relevant)
704 then a backtrace is printed when a run-time error occurs.
705 To disable the backtracing, set the variable to
706 @samp{n}, @samp{N}, @samp{0}. Default is not to print a backtrace
707 unless the @option{-fbacktrace} compile option
710 @c =====================================================================
711 @c PART II: LANGUAGE REFERENCE
712 @c =====================================================================
715 \part{II}{Language Reference}
718 @c ---------------------------------------------------------------------
719 @c Fortran 2003 Status
720 @c ---------------------------------------------------------------------
722 @node Fortran 2003 status
723 @chapter Fortran 2003 Status
725 Although GNU Fortran focuses on implementing the Fortran 95
726 standard for the time being, a few Fortran 2003 features are currently
731 Intrinsics @code{command_argument_count}, @code{get_command},
732 @code{get_command_argument}, @code{get_environment_variable}, and
736 @cindex array, constructors
738 Array constructors using square brackets. That is, @code{[...]} rather
742 @cindex @code{FLUSH} statement
743 @cindex statement, @code{FLUSH}
744 @code{FLUSH} statement.
747 @cindex @code{IOMSG=} specifier
748 @code{IOMSG=} specifier for I/O statements.
751 @cindex @code{ENUM} statement
752 @cindex @code{ENUMERATOR} statement
753 @cindex statement, @code{ENUM}
754 @cindex statement, @code{ENUMERATOR}
755 @opindex @code{fshort-enums}
756 Support for the declaration of enumeration constants via the
757 @code{ENUM} and @code{ENUMERATOR} statements. Interoperability with
758 @command{gcc} is guaranteed also for the case where the
759 @command{-fshort-enums} command line option is given.
766 @cindex @code{ALLOCATABLE} dummy arguments
767 @code{ALLOCATABLE} dummy arguments.
769 @cindex @code{ALLOCATABLE} function results
770 @code{ALLOCATABLE} function results
772 @cindex @code{ALLOCATABLE} components of derived types
773 @code{ALLOCATABLE} components of derived types
777 @cindex @code{STREAM} I/O
778 @cindex @code{ACCESS='STREAM'} I/O
779 The @code{OPEN} statement supports the @code{ACCESS='STREAM'} specifier,
780 allowing I/O without any record structure.
783 Namelist input/output for internal files.
786 @cindex @code{PROTECTED} statement
787 @cindex statement, @code{PROTECTED}
788 The @code{PROTECTED} statement and attribute.
791 @cindex @code{VALUE} statement
792 @cindex statement, @code{VALUE}
793 The @code{VALUE} statement and attribute.
796 @cindex @code{VOLATILE} statement
797 @cindex statement, @code{VOLATILE}
798 The @code{VOLATILE} statement and attribute.
801 @cindex @code{IMPORT} statement
802 @cindex statement, @code{IMPORT}
803 The @code{IMPORT} statement, allowing to import
804 host-associated derived types.
807 @cindex @code{USE, INTRINSIC} statement
808 @cindex statement, @code{USE, INTRINSIC}
809 @cindex @code{ISO_FORTRAN_ENV} statement
810 @cindex statement, @code{ISO_FORTRAN_ENV}
811 @code{USE} statement with @code{INTRINSIC} and @code{NON_INTRINSIC}
812 attribute; supported intrinsic modules: @code{ISO_FORTRAN_ENV},
813 @code{OMP_LIB} and @code{OMP_LIB_KINDS}.
816 Renaming of operators in the @code{USE} statement.
821 @c ---------------------------------------------------------------------
823 @c ---------------------------------------------------------------------
825 @c Maybe this chapter should be merged with the 'Standards' section,
826 @c whenever that is written :-)
832 GNU Fortran implements a number of extensions over standard
833 Fortran. This chapter contains information on their syntax and
834 meaning. There are currently two categories of GNU Fortran
835 extensions, those that provide functionality beyond that provided
836 by any standard, and those that are supported by GNU Fortran
837 purely for backward compatibility with legacy compilers. By default,
838 @option{-std=gnu} allows the compiler to accept both types of
839 extensions, but to warn about the use of the latter. Specifying
840 either @option{-std=f95} or @option{-std=f2003} disables both types
841 of extensions, and @option{-std=legacy} allows both without warning.
844 * Old-style kind specifications::
845 * Old-style variable initialization::
846 * Extensions to namelist::
847 * X format descriptor without count field::
848 * Commas in FORMAT specifications::
849 * Missing period in FORMAT specifications::
851 * BOZ literal constants::
852 * Real array indices::
854 * Implicitly convert LOGICAL and INTEGER values::
855 * Hollerith constants support::
857 * CONVERT specifier::
859 * Argument list functions::
862 @node Old-style kind specifications
863 @section Old-style kind specifications
864 @cindex kind, old-style
866 GNU Fortran allows old-style kind specifications in declarations. These
872 where @code{TYPESPEC} is a basic type (@code{INTEGER}, @code{REAL},
873 etc.), and where @code{size} is a byte count corresponding to the
874 storage size of a valid kind for that type. (For @code{COMPLEX}
875 variables, @code{size} is the total size of the real and imaginary
876 parts.) The statement then declares @code{x}, @code{y} and @code{z} to
877 be of type @code{TYPESPEC} with the appropriate kind. This is
878 equivalent to the standard-conforming declaration
883 where @code{k} is equal to @code{size} for most types, but is equal to
884 @code{size/2} for the @code{COMPLEX} type.
886 @node Old-style variable initialization
887 @section Old-style variable initialization
889 GNU Fortran allows old-style initialization of variables of the
893 REAL x(2,2) /3*0.,1./
895 The syntax for the initializers is as for the @code{DATA} statement, but
896 unlike in a @code{DATA} statement, an initializer only applies to the
897 variable immediately preceding the initialization. In other words,
898 something like @code{INTEGER I,J/2,3/} is not valid. This style of
899 initialization is only allowed in declarations without double colons
900 (@code{::}); the double colons were introduced in Fortran 90, which also
901 introduced a standard syntax for initializing variables in type
904 Examples of standard-conforming code equivalent to the above example
908 INTEGER :: i = 1, j = 2
909 REAL :: x(2,2) = RESHAPE((/0.,0.,0.,1./),SHAPE(x))
913 DATA i/1/, j/2/, x/3*0.,1./
916 Note that variables which are explicitly initialized in declarations
917 or in @code{DATA} statements automatically acquire the @code{SAVE}
920 @node Extensions to namelist
921 @section Extensions to namelist
924 GNU Fortran fully supports the Fortran 95 standard for namelist I/O
925 including array qualifiers, substrings and fully qualified derived types.
926 The output from a namelist write is compatible with namelist read. The
927 output has all names in upper case and indentation to column 1 after the
928 namelist name. Two extensions are permitted:
930 Old-style use of @samp{$} instead of @samp{&}
933 X(:)%Y(2) = 1.0 2.0 3.0
938 It should be noted that the default terminator is @samp{/} rather than
941 Querying of the namelist when inputting from stdin. After at least
942 one space, entering @samp{?} sends to stdout the namelist name and the names of
943 the variables in the namelist:
954 Entering @samp{=?} outputs the namelist to stdout, as if
955 @code{WRITE(*,NML = mynml)} had been called:
960 X(1)%Y= 0.000000 , 1.000000 , 0.000000 ,
961 X(2)%Y= 0.000000 , 2.000000 , 0.000000 ,
962 X(3)%Y= 0.000000 , 3.000000 , 0.000000 ,
966 To aid this dialog, when input is from stdin, errors send their
967 messages to stderr and execution continues, even if @code{IOSTAT} is set.
969 @code{PRINT} namelist is permitted. This causes an error if
970 @option{-std=f95} is used.
973 REAL, dimension (4) :: x = (/1.0, 2.0, 3.0, 4.0/)
976 END PROGRAM test_print
979 Expanded namelist reads are permitted. This causes an error if
980 @option{-std=f95} is used. In the following example, the first element
981 of the array will be given the value 0.00 and the two succeeding
982 elements will be given the values 1.00 and 2.00.
985 X(1,1) = 0.00 , 1.00 , 2.00
989 @node X format descriptor without count field
990 @section @code{X} format descriptor without count field
992 To support legacy codes, GNU Fortran permits the count field of the
993 @code{X} edit descriptor in @code{FORMAT} statements to be omitted.
994 When omitted, the count is implicitly assumed to be one.
998 10 FORMAT (I1, X, I1)
1001 @node Commas in FORMAT specifications
1002 @section Commas in @code{FORMAT} specifications
1004 To support legacy codes, GNU Fortran allows the comma separator
1005 to be omitted immediately before and after character string edit
1006 descriptors in @code{FORMAT} statements.
1010 10 FORMAT ('FOO='I1' BAR='I2)
1014 @node Missing period in FORMAT specifications
1015 @section Missing period in @code{FORMAT} specifications
1017 To support legacy codes, GNU Fortran allows missing periods in format
1018 specifications if and only if @option{-std=legacy} is given on the
1019 command line. This is considered non-conforming code and is
1028 @node I/O item lists
1029 @section I/O item lists
1030 @cindex I/O item lists
1032 To support legacy codes, GNU Fortran allows the input item list
1033 of the @code{READ} statement, and the output item lists of the
1034 @code{WRITE} and @code{PRINT} statements, to start with a comma.
1036 @node BOZ literal constants
1037 @section BOZ literal constants
1038 @cindex BOZ literal constants
1040 As an extension, GNU Fortran allows hexadecimal BOZ literal constants to
1041 be specified using the X prefix, in addition to the standard Z prefix.
1042 BOZ literal constants can also be specified by adding a suffix to the
1043 string. For example, @code{Z'ABC'} and @code{'ABC'Z} are equivalent.
1045 The Fortran standard restricts the appearance of a BOZ literal constant
1046 to the @code{DATA} statement, and it is expected to be assigned to an
1047 @code{INTEGER} variable. GNU Fortran permits a BOZ literal to appear in
1048 any initialization expression as well as assignment statements.
1050 Attempts to use a BOZ literal constant to do a bitwise initialization of
1051 a variable can lead to confusion. A BOZ literal constant is converted
1052 to an @code{INTEGER} value with the kind type with the largest decimal
1053 representation, and this value is then converted numerically to the type
1054 and kind of the variable in question. Thus, one should not expect a
1055 bitwise copy of the BOZ literal constant to be assigned to a @code{REAL}
1058 Similarly, initializing an @code{INTEGER} variable with a statement such
1059 as @code{DATA i/Z'FFFFFFFF'/} will produce an integer overflow rather
1060 than the desired result of @math{-1} when @code{i} is a 32-bit integer
1061 on a system that supports 64-bit integers. The @samp{-fno-range-check}
1062 option can be used as a workaround for legacy code that initializes
1063 integers in this manner.
1065 @node Real array indices
1066 @section Real array indices
1067 @cindex array, indices of type real
1069 As an extension, GNU Fortran allows the use of @code{REAL} expressions
1070 or variables as array indices.
1072 @node Unary operators
1073 @section Unary operators
1074 @cindex operators, unary
1076 As an extension, GNU Fortran allows unary plus and unary minus operators
1077 to appear as the second operand of binary arithmetic operators without
1078 the need for parenthesis.
1084 @node Implicitly convert LOGICAL and INTEGER values
1085 @section Implicitly convert @code{LOGICAL} and @code{INTEGER} values
1086 @cindex conversion, to integer
1087 @cindex conversion, to logical
1089 As an extension for backwards compatibility with other compilers, GNU
1090 Fortran allows the implicit conversion of @code{LOGICAL} values to
1091 @code{INTEGER} values and vice versa. When converting from a
1092 @code{LOGICAL} to an @code{INTEGER}, @code{.FALSE.} is interpreted as
1093 zero, and @code{.TRUE.} is interpreted as one. When converting from
1094 @code{INTEGER} to @code{LOGICAL}, the value zero is interpreted as
1095 @code{.FALSE.} and any nonzero value is interpreted as @code{.TRUE.}.
1099 IF (i) PRINT *, 'True'
1102 @node Hollerith constants support
1103 @section Hollerith constants support
1104 @cindex Hollerith constants
1106 GNU Fortran supports Hollerith constants in assignments, function
1107 arguments, and @code{DATA} and @code{ASSIGN} statements. A Hollerith
1108 constant is written as a string of characters preceded by an integer
1109 constant indicating the character count, and the letter @code{H} or
1110 @code{h}, and stored in bytewise fashion in a numeric (@code{INTEGER},
1111 @code{REAL}, or @code{complex}) or @code{LOGICAL} variable. The
1112 constant will be padded or truncated to fit the size of the variable in
1115 Examples of valid uses of Hollerith constants:
1118 data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
1119 x(1) = 16HABCDEFGHIJKLMNOP
1123 Invalid Hollerith constants examples:
1126 a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
1127 a = 0H ! At least one character is needed.
1130 In general, Hollerith constants were used to provide a rudimentary
1131 facility for handling character strings in early Fortran compilers,
1132 prior to the introduction of @code{CHARACTER} variables in Fortran 77;
1133 in those cases, the standard-compliant equivalent is to convert the
1134 program to use proper character strings. On occasion, there may be a
1135 case where the intent is specifically to initialize a numeric variable
1136 with a given byte sequence. In these cases, the same result can be
1137 obtained by using the @code{TRANSFER} statement, as in this example.
1139 INTEGER(KIND=4) :: a
1140 a = TRANSFER ("abcd", a) ! equivalent to: a = 4Habcd
1145 @section Cray pointers
1146 @cindex pointer, cray
1148 Cray pointers are part of a non-standard extension that provides a
1149 C-like pointer in Fortran. This is accomplished through a pair of
1150 variables: an integer "pointer" that holds a memory address, and a
1151 "pointee" that is used to dereference the pointer.
1153 Pointer/pointee pairs are declared in statements of the form:
1155 pointer ( <pointer> , <pointee> )
1159 pointer ( <pointer1> , <pointee1> ), ( <pointer2> , <pointee2> ), ...
1161 The pointer is an integer that is intended to hold a memory address.
1162 The pointee may be an array or scalar. A pointee can be an assumed
1163 size array---that is, the last dimension may be left unspecified by
1164 using a @code{*} in place of a value---but a pointee cannot be an
1165 assumed shape array. No space is allocated for the pointee.
1167 The pointee may have its type declared before or after the pointer
1168 statement, and its array specification (if any) may be declared
1169 before, during, or after the pointer statement. The pointer may be
1170 declared as an integer prior to the pointer statement. However, some
1171 machines have default integer sizes that are different than the size
1172 of a pointer, and so the following code is not portable:
1177 If a pointer is declared with a kind that is too small, the compiler
1178 will issue a warning; the resulting binary will probably not work
1179 correctly, because the memory addresses stored in the pointers may be
1180 truncated. It is safer to omit the first line of the above example;
1181 if explicit declaration of ipt's type is omitted, then the compiler
1182 will ensure that ipt is an integer variable large enough to hold a
1185 Pointer arithmetic is valid with Cray pointers, but it is not the same
1186 as C pointer arithmetic. Cray pointers are just ordinary integers, so
1187 the user is responsible for determining how many bytes to add to a
1188 pointer in order to increment it. Consider the following example:
1192 pointer (ipt, pointee)
1196 The last statement does not set @code{ipt} to the address of
1197 @code{target(1)}, as it would in C pointer arithmetic. Adding @code{1}
1198 to @code{ipt} just adds one byte to the address stored in @code{ipt}.
1200 Any expression involving the pointee will be translated to use the
1201 value stored in the pointer as the base address.
1203 To get the address of elements, this extension provides an intrinsic
1204 function @code{LOC()}. The @code{LOC()} function is equivalent to the
1205 @code{&} operator in C, except the address is cast to an integer type:
1208 pointer(ipt, arpte(10))
1210 ipt = loc(ar) ! Makes arpte is an alias for ar
1211 arpte(1) = 1.0 ! Sets ar(1) to 1.0
1213 The pointer can also be set by a call to the @code{MALLOC} intrinsic
1216 Cray pointees often are used to alias an existing variable. For
1224 As long as @code{ipt} remains unchanged, @code{iarr} is now an alias for
1225 @code{target}. The optimizer, however, will not detect this aliasing, so
1226 it is unsafe to use @code{iarr} and @code{target} simultaneously. Using
1227 a pointee in any way that violates the Fortran aliasing rules or
1228 assumptions is illegal. It is the user's responsibility to avoid doing
1229 this; the compiler works under the assumption that no such aliasing
1232 Cray pointers will work correctly when there is no aliasing (i.e., when
1233 they are used to access a dynamically allocated block of memory), and
1234 also in any routine where a pointee is used, but any variable with which
1235 it shares storage is not used. Code that violates these rules may not
1236 run as the user intends. This is not a bug in the optimizer; any code
1237 that violates the aliasing rules is illegal. (Note that this is not
1238 unique to GNU Fortran; any Fortran compiler that supports Cray pointers
1239 will ``incorrectly'' optimize code with illegal aliasing.)
1241 There are a number of restrictions on the attributes that can be applied
1242 to Cray pointers and pointees. Pointees may not have the
1243 @code{ALLOCATABLE}, @code{INTENT}, @code{OPTIONAL}, @code{DUMMY},
1244 @code{TARGET}, @code{INTRINSIC}, or @code{POINTER} attributes. Pointers
1245 may not have the @code{DIMENSION}, @code{POINTER}, @code{TARGET},
1246 @code{ALLOCATABLE}, @code{EXTERNAL}, or @code{INTRINSIC} attributes.
1247 Pointees may not occur in more than one pointer statement. A pointee
1248 cannot be a pointer. Pointees cannot occur in equivalence, common, or
1251 A Cray pointer may also point to a function or a subroutine. For
1252 example, the following excerpt is valid:
1256 pointer (subptr,subpte)
1266 A pointer may be modified during the course of a program, and this
1267 will change the location to which the pointee refers. However, when
1268 pointees are passed as arguments, they are treated as ordinary
1269 variables in the invoked function. Subsequent changes to the pointer
1270 will not change the base address of the array that was passed.
1272 @node CONVERT specifier
1273 @section CONVERT specifier
1274 @cindex CONVERT specifier
1276 GNU Fortran allows the conversion of unformatted data between little-
1277 and big-endian representation to facilitate moving of data
1278 between different systems. The conversion can be indicated with
1279 the @code{CONVERT} specifier on the @code{OPEN} statement.
1280 @xref{GFORTRAN_CONVERT_UNIT}, for an alternative way of specifying
1281 the data format via an environment variable.
1283 Valid values for @code{CONVERT} are:
1285 @item @code{CONVERT='NATIVE'} Use the native format. This is the default.
1286 @item @code{CONVERT='SWAP'} Swap between little- and big-endian.
1287 @item @code{CONVERT='LITTLE_ENDIAN'} Use the little-endian representation
1288 for unformatted files.
1289 @item @code{CONVERT='BIG_ENDIAN'} Use the big-endian representation for
1293 Using the option could look like this:
1295 open(file='big.dat',form='unformatted',access='sequential', &
1296 convert='big_endian')
1299 The value of the conversion can be queried by using
1300 @code{INQUIRE(CONVERT=ch)}. The values returned are
1301 @code{'BIG_ENDIAN'} and @code{'LITTLE_ENDIAN'}.
1303 @code{CONVERT} works between big- and little-endian for
1304 @code{INTEGER} values of all supported kinds and for @code{REAL}
1305 on IEEE systems of kinds 4 and 8. Conversion between different
1306 ``extended double'' types on different architectures such as
1307 m68k and x86_64, which GNU Fortran
1308 supports as @code{REAL(KIND=10)} and @code{REAL(KIND=16)}, will
1311 @emph{Note that the values specified via the GFORTRAN_CONVERT_UNIT
1312 environment variable will override the CONVERT specifier in the
1313 open statement}. This is to give control over data formats to
1314 users who do not have the source code of their program available.
1316 Using anything but the native representation for unformatted data
1317 carries a significant speed overhead. If speed in this area matters
1318 to you, it is best if you use this only for data that needs to be
1325 GNU Fortran attempts to be OpenMP Application Program Interface v2.5
1326 compatible when invoked with the @option{-fopenmp} option. GNU Fortran
1327 then generates parallelized code according to the OpenMP directives
1328 used in the source. The OpenMP Fortran runtime library
1329 routines are provided both in a form of a Fortran 90 module named
1330 @code{omp_lib} and in a form of a Fortran @code{include} file named
1333 For details refer to the actual
1334 @uref{http://www.openmp.org/drupal/mp-documents/spec25.pdf,
1335 OpenMP Application Program Interface v2.5} specification.
1337 @node Argument list functions
1338 @section Argument list functions %VAL, %REF and %LOC
1339 @cindex argument list functions
1344 GNU Fortran supports argument list functions @code{%VAL}, @code{%REF}
1345 and @code{%LOC} statements, for backward compatibility with g77.
1346 It is recommended that these should be used only for code that is
1347 accessing facilities outside of GNU Fortran, such as operating system
1348 or windowing facilities. It is best to constrain such uses to isolated
1349 portions of a program--portions that deal specifically and exclusively
1350 with low-level, system-dependent facilities. Such portions might well
1351 provide a portable interface for use by the program as a whole, but are
1352 themselves not portable, and should be thoroughly tested each time they
1353 are rebuilt using a new compiler or version of a compiler.
1355 @code{%VAL} passes a scalar argument by value, @code{%REF} passes it by
1356 reference and @code{%LOC} passes its memory location. Since gfortran
1357 already passes scalar arguments by reference, @code{%REF} is in effect
1358 a do-nothing. @code{%LOC} has the same effect as a fortran pointer.
1360 An example of passing an argument by value to a C subroutine foo.:
1363 C prototype void foo_ (float x);
1372 For details refer to the g77 manual
1373 @uref{http://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/index.html#Top}.
1375 Also, the gfortran testsuite c_by_val.f and its partner c_by_val.c are
1378 @c ---------------------------------------------------------------------
1379 @c Intrinsic Procedures
1380 @c ---------------------------------------------------------------------
1382 @include intrinsic.texi
1389 @c ---------------------------------------------------------------------
1391 @c ---------------------------------------------------------------------
1394 @unnumbered Contributing
1395 @cindex Contributing
1397 Free software is only possible if people contribute to efforts
1399 We're always in need of more people helping out with ideas
1400 and comments, writing documentation and contributing code.
1402 If you want to contribute to GNU Fortran,
1403 have a look at the long lists of projects you can take on.
1404 Some of these projects are small,
1405 some of them are large;
1406 some are completely orthogonal to the rest of what is
1407 happening on GNU Fortran,
1408 but others are ``mainstream'' projects in need of enthusiastic hackers.
1409 All of these projects are important!
1410 We'll eventually get around to the things here,
1411 but they are also things doable by someone who is willing and able.
1416 * Proposed Extensions::
1421 @section Contributors to GNU Fortran
1422 @cindex Contributors
1426 Most of the parser was hand-crafted by @emph{Andy Vaught}, who is
1427 also the initiator of the whole project. Thanks Andy!
1428 Most of the interface with GCC was written by @emph{Paul Brook}.
1430 The following individuals have contributed code and/or
1431 ideas and significant help to the GNU Fortran project
1432 (in no particular order):
1436 @item Katherine Holcomb
1437 @item Tobias Schl@"uter
1438 @item Steven Bosscher
1441 @item Niels Kristian Bech Jensen
1442 @item Steven Johnson
1447 @item Fran@,{c}ois-Xavier Coudert
1448 @item Steven G. Kargl
1450 @item Janne Blomqvist
1457 @item Richard Henderson
1458 @item Richard Sandiford
1459 @item Richard Guenther
1460 @item Bernhard Fischer
1463 The following people have contributed bug reports,
1464 smaller or larger patches,
1465 and much needed feedback and encouragement for the
1466 GNU Fortran project:
1469 @item Erik Schnetter
1474 Many other individuals have helped debug,
1475 test and improve the GNU Fortran compiler over the past few years,
1476 and we welcome you to do the same!
1477 If you already have done so,
1478 and you would like to see your name listed in the
1479 list above, please contact us.
1487 @item Help build the test suite
1488 Solicit more code for donation to the test suite.
1489 We can keep code private on request.
1491 @item Bug hunting/squishing
1492 Find bugs and write more test cases!
1493 Test cases are especially very welcome,
1494 because it allows us to concentrate on fixing bugs
1495 instead of isolating them.
1497 @item Smaller projects (``bug'' fixes):
1499 @item Allow init exprs to be numbers raised to integer powers.
1500 @item Implement correct rounding.
1501 @item Implement F restrictions on Fortran 95 syntax.
1502 @item See about making Emacs-parsable error messages.
1506 If you wish to work on the runtime libraries,
1507 please contact a project maintainer.
1511 @node Proposed Extensions
1512 @section Proposed Extensions
1514 Here's a list of proposed extensions for the GNU Fortran compiler, in no particular
1515 order. Most of these are necessary to be fully compatible with
1516 existing Fortran compilers, but they are not part of the official
1517 J3 Fortran 95 standard.
1519 @subsection Compiler extensions:
1522 User-specified alignment rules for structures.
1525 Flag to generate @code{Makefile} info.
1528 Automatically extend single precision constants to double.
1531 Compile code that conserves memory by dynamically allocating common and
1532 module storage either on stack or heap.
1535 Compile flag to generate code for array conformance checking (suggest -CC).
1538 User control of symbol names (underscores, etc).
1541 Compile setting for maximum size of stack frame size before spilling
1542 parts to static or heap.
1545 Flag to force local variables into static space.
1548 Flag to force local variables onto stack.
1551 Flag for maximum errors before ending compile.
1554 Option to initialize otherwise uninitialized integer and floating
1559 @subsection Environment Options
1562 Pluggable library modules for random numbers, linear algebra.
1563 LA should use BLAS calling conventions.
1566 Environment variables controlling actions on arithmetic exceptions like
1567 overflow, underflow, precision loss---Generate NaN, abort, default.
1571 Set precision for fp units that support it (i387).
1574 Variable for setting fp rounding mode.
1577 Variable to fill uninitialized variables with a user-defined bit
1581 Environment variable controlling filename that is opened for that unit
1585 Environment variable to clear/trash memory being freed.
1588 Environment variable to control tracing of allocations and frees.
1591 Environment variable to display allocated memory at normal program end.
1594 Environment variable for filename for * IO-unit.
1597 Environment variable for temporary file directory.
1600 Environment variable forcing standard output to be line buffered (unix).
1605 @c ---------------------------------------------------------------------
1606 @c GNU General Public License
1607 @c ---------------------------------------------------------------------
1613 @c ---------------------------------------------------------------------
1614 @c GNU Free Documentation License
1615 @c ---------------------------------------------------------------------
1621 @c ---------------------------------------------------------------------
1622 @c Funding Free Software
1623 @c ---------------------------------------------------------------------
1625 @include funding.texi
1627 @c ---------------------------------------------------------------------
1629 @c ---------------------------------------------------------------------
1632 @unnumbered Option Index
1633 @command{gfortran}'s command line options are indexed here without any
1634 initial @samp{-} or @samp{--}. Where an option has both positive and
1635 negative forms (such as -foption and -fno-option), relevant entries in
1636 the manual are indexed under the most appropriate form; it may sometimes
1637 be useful to look up both forms.
1641 @unnumbered Keyword Index