1 @c Copyright (C) 2004, 2005, 2006, 2007, 2008
2 @c Free Software Foundation, Inc.
3 @c This is part of the GNU Fortran manual.
4 @c For copying conditions, see the file gfortran.texi.
8 Copyright @copyright{} 2004, 2005, 2006, 2007, 2008
9 Free Software Foundation, Inc.
11 Permission is granted to copy, distribute and/or modify this document
12 under the terms of the GNU Free Documentation License, Version 1.2 or
13 any later version published by the Free Software Foundation; with the
14 Invariant Sections being ``Funding Free Software'', the Front-Cover
15 Texts being (a) (see below), and with the Back-Cover Texts being (b)
16 (see below). A copy of the license is included in the gfdl(7) man page.
18 (a) The FSF's Front-Cover Text is:
22 (b) The FSF's Back-Cover Text is:
24 You have freedom to copy and modify this GNU Manual, like GNU
25 software. Copies published by the Free Software Foundation raise
26 funds for GNU development.
28 @c Set file name and title for the man page.
30 @settitle GNU Fortran compiler.
32 gfortran [@option{-c}|@option{-S}|@option{-E}]
33 [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
34 [@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
35 [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
36 [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
37 [@option{-f}@var{option}@dots{}]
38 [@option{-m}@var{machine-option}@dots{}]
39 [@option{-o} @var{outfile}] @var{infile}@dots{}
41 Only the most useful options are listed here; see below for the
45 gpl(7), gfdl(7), fsf-funding(7),
46 cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
47 and the Info entries for @file{gcc}, @file{cpp}, @file{gfortran}, @file{as},
48 @file{ld}, @file{binutils} and @file{gdb}.
51 For instructions on reporting bugs, see
55 See the Info entry for @command{gfortran} for contributors to GCC and
60 @node Invoking GNU Fortran
61 @chapter GNU Fortran Command Options
62 @cindex GNU Fortran command options
63 @cindex command options
64 @cindex options, @command{gfortran} command
66 @c man begin DESCRIPTION
68 The @command{gfortran} command supports all the options supported by the
69 @command{gcc} command. Only options specific to GNU Fortran are documented here.
71 @xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
72 Collection (GCC)}, for information
73 on the non-Fortran-specific aspects of the @command{gcc} command (and,
74 therefore, the @command{gfortran} command).
76 @cindex options, negative forms
77 All GCC and GNU Fortran options
78 are accepted both by @command{gfortran} and by @command{gcc}
79 (as well as any other drivers built at the same time,
80 such as @command{g++}),
81 since adding GNU Fortran to the GCC distribution
82 enables acceptance of GNU Fortran options
83 by all of the relevant drivers.
85 In some cases, options have positive and negative forms;
86 the negative form of @option{-ffoo} would be @option{-fno-foo}.
87 This manual documents only one of these two forms, whichever
88 one is not the default.
92 * Option Summary:: Brief list of all @command{gfortran} options,
94 * Fortran Dialect Options:: Controlling the variant of Fortran language
96 * Preprocessing Options:: Enable and customize preprocessing.
97 * Error and Warning Options:: How picky should the compiler be?
98 * Debugging Options:: Symbol tables, measurements, and debugging dumps.
99 * Directory Options:: Where to find module files
100 * Link Options :: Influencing the linking step
101 * Runtime Options:: Influencing runtime behavior
102 * Code Gen Options:: Specifying conventions for function calls, data layout
104 * Environment Variables:: Environment variables that affect @command{gfortran}.
108 @section Option summary
112 Here is a summary of all the options specific to GNU Fortran, grouped
113 by type. Explanations are in the following sections.
116 @item Fortran Language Options
117 @xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
118 @gccoptlist{-fall-intrinsics -ffree-form -fno-fixed-form @gol
119 -fdollar-ok -fimplicit-none -fmax-identifier-length @gol
120 -std=@var{std} -fd-lines-as-code -fd-lines-as-comments @gol
121 -ffixed-line-length-@var{n} -ffixed-line-length-none @gol
122 -ffree-line-length-@var{n} -ffree-line-length-none @gol
123 -fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
124 -fcray-pointer -fopenmp -fno-range-check -fbackslash -fmodule-private}
126 @item Preprocessing Options
127 @xref{Preprocessing Options,,Enable and customize preprocessing}.
128 @gccoptlist{-cpp -dD -dI -dM -dN -dU -fworking-directory @gol
129 -imultilib @var{dir} -iprefix @var{file} -isysroot @var{dir} @gol
130 -iquote -isystem @var{dir} -nocpp -nostdinc -undef @gol
131 -A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol
132 -C -CC -D@var{macro}@r{[}=@var{defn}@r{]} -U@var{macro} -H -P}
134 @item Error and Warning Options
135 @xref{Error and Warning Options,,Options to request or suppress errors
137 @gccoptlist{-fmax-errors=@var{n} @gol
138 -fsyntax-only -pedantic -pedantic-errors @gol
139 -Wall -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol
140 -Wconversion -Wimplicit-interface -Wline-truncation -Wintrinsics-std @gol
141 -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter -Wintrinsics-shadow @gol
144 @item Debugging Options
145 @xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
146 @gccoptlist{-fdump-parse-tree -ffpe-trap=@var{list} @gol
147 -fdump-core -fbacktrace}
149 @item Directory Options
150 @xref{Directory Options,,Options for directory search}.
151 @gccoptlist{-I@var{dir} -J@var{dir} -M@var{dir} -fintrinsic-modules-path @var{dir}}
154 @xref{Link Options,,Options for influencing the linking step}.
155 @gccoptlist{-static-libgfortran}
157 @item Runtime Options
158 @xref{Runtime Options,,Options for influencing runtime behavior}.
159 @gccoptlist{-fconvert=@var{conversion} -fno-range-check
160 -frecord-marker=@var{length} @gol -fmax-subrecord-length=@var{length}
163 @item Code Generation Options
164 @xref{Code Gen Options,,Options for code generation conventions}.
165 @gccoptlist{-fno-automatic -ff2c -fno-underscoring
166 -fsecond-underscore @gol
167 -fbounds-check -fcheck-array-temporaries -fmax-stack-var-size=@var{n} @gol
168 -fpack-derived -frepack-arrays -fshort-enums -fexternal-blas @gol
169 -fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol
170 -finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan>} @gol
171 -finit-logical=@var{<true|false>} -finit-character=@var{n} -fno-align-commons}
175 * Fortran Dialect Options:: Controlling the variant of Fortran language
177 * Preprocessing Options:: Enable and customize preprocessing.
178 * Error and Warning Options:: How picky should the compiler be?
179 * Debugging Options:: Symbol tables, measurements, and debugging dumps.
180 * Directory Options:: Where to find module files
181 * Link Options :: Influencing the linking step
182 * Runtime Options:: Influencing runtime behavior
183 * Code Gen Options:: Specifying conventions for function calls, data layout
187 @node Fortran Dialect Options
188 @section Options controlling Fortran dialect
189 @cindex dialect options
190 @cindex language, dialect options
191 @cindex options, dialect
193 The following options control the details of the Fortran dialect
194 accepted by the compiler:
199 @opindex @code{ffree-form}
200 @opindex @code{fno-fixed-form}
201 @cindex options, fortran dialect
202 @cindex file format, free
203 @cindex file format, fixed
204 Specify the layout used by the source file. The free form layout
205 was introduced in Fortran 90. Fixed form was traditionally used in
206 older Fortran programs. When neither option is specified, the source
207 form is determined by the file extension.
209 @item -fall-intrinsics
210 @opindex @code{fall-intrinsics}
211 Accept all of the intrinsic procedures provided in libgfortran
212 without regard to the setting of @option{-std}. In particular,
213 this option can be quite useful with @option{-std=f95}. Additionally,
214 @command{gfortran} will ignore @option{-Wintrinsics-std} and will never try
215 to link to an @code{EXTERNAL} version if the intrinsic is not included in the
218 @item -fd-lines-as-code
219 @item -fd-lines-as-comments
220 @opindex @code{fd-lines-as-code}
221 @opindex @code{fd-lines-as-comments}
222 Enable special treatment for lines beginning with @code{d} or @code{D}
223 in fixed form sources. If the @option{-fd-lines-as-code} option is
224 given they are treated as if the first column contained a blank. If the
225 @option{-fd-lines-as-comments} option is given, they are treated as
228 @item -fdefault-double-8
229 @opindex @code{fdefault-double-8}
230 Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.
232 @item -fdefault-integer-8
233 @opindex @code{fdefault-integer-8}
234 Set the default integer and logical types to an 8 byte wide type.
235 Do nothing if this is already the default.
237 @item -fdefault-real-8
238 @opindex @code{fdefault-real-8}
239 Set the default real type to an 8 byte wide type.
240 Do nothing if this is already the default.
243 @opindex @code{fdollar-ok}
246 @cindex character set
247 Allow @samp{$} as a valid character in a symbol name.
250 @opindex @code{backslash}
252 @cindex escape characters
253 Change the interpretation of backslashes in string literals from a single
254 backslash character to ``C-style'' escape characters. The following
255 combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n},
256 @code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII
257 characters alert, backspace, form feed, newline, carriage return,
258 horizontal tab, vertical tab, backslash, and NUL, respectively.
259 Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and
260 @code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are
261 translated into the Unicode characters corresponding to the specified code
262 points. All other combinations of a character preceded by \ are
265 @item -fmodule-private
266 @opindex @code{fmodule-private}
267 @cindex module entities
269 Set the default accessibility of module entities to @code{PRIVATE}.
270 Use-associated entities will not be accessible unless they are explicitly
271 declared as @code{PUBLIC}.
273 @item -ffixed-line-length-@var{n}
274 @opindex @code{ffixed-line-length-}@var{n}
275 @cindex file format, fixed
276 Set column after which characters are ignored in typical fixed-form
277 lines in the source file, and through which spaces are assumed (as
278 if padded to that length) after the ends of short fixed-form lines.
280 Popular values for @var{n} include 72 (the
281 standard and the default), 80 (card image), and 132 (corresponding
282 to ``extended-source'' options in some popular compilers).
283 @var{n} may also be @samp{none}, meaning that the entire line is meaningful
284 and that continued character constants never have implicit spaces appended
285 to them to fill out the line.
286 @option{-ffixed-line-length-0} means the same thing as
287 @option{-ffixed-line-length-none}.
289 @item -ffree-line-length-@var{n}
290 @opindex @code{ffree-line-length-}@var{n}
291 @cindex file format, free
292 Set column after which characters are ignored in typical free-form
293 lines in the source file. The default value is 132.
294 @var{n} may be @samp{none}, meaning that the entire line is meaningful.
295 @option{-ffree-line-length-0} means the same thing as
296 @option{-ffree-line-length-none}.
298 @item -fmax-identifier-length=@var{n}
299 @opindex @code{fmax-identifier-length=}@var{n}
300 Specify the maximum allowed identifier length. Typical values are
301 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
303 @item -fimplicit-none
304 @opindex @code{fimplicit-none}
305 Specify that no implicit typing is allowed, unless overridden by explicit
306 @code{IMPLICIT} statements. This is the equivalent of adding
307 @code{implicit none} to the start of every procedure.
310 @opindex @code{fcray-pointer}
311 Enable the Cray pointer extension, which provides C-like pointer
315 @opindex @code{fopenmp}
317 Enable the OpenMP extensions. This includes OpenMP @code{!$omp} directives
319 and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
320 @code{!$} conditional compilation sentinels in free form
321 and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form,
322 and when linking arranges for the OpenMP runtime library to be linked
323 in. The option @option{-fopenmp} implies @option{-frecursive}.
325 @item -fno-range-check
326 @opindex @code{frange-check}
327 Disable range checking on results of simplification of constant
328 expressions during compilation. For example, GNU Fortran will give
329 an error at compile time when simplifying @code{a = 1. / 0}.
330 With this option, no error will be given and @code{a} will be assigned
331 the value @code{+Infinity}. If an expression evaluates to a value
332 outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}],
333 then the expression will be replaced by @code{-Inf} or @code{+Inf}
335 Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow
336 on most systems, but with @option{-fno-range-check} the value will
337 ``wrap around'' and @code{i} will be initialized to @math{-1} instead.
340 @opindex @code{std=}@var{std} option
341 Specify the standard to which the program is expected to conform, which
342 may be one of @samp{f95}, @samp{f2003}, @samp{f2008}, @samp{gnu}, or
343 @samp{legacy}. The default value for @var{std} is @samp{gnu}, which
344 specifies a superset of the Fortran 95 standard that includes all of the
345 extensions supported by GNU Fortran, although warnings will be given for
346 obsolete extensions not recommended for use in new code. The
347 @samp{legacy} value is equivalent but without the warnings for obsolete
348 extensions, and may be useful for old non-standard programs. The
349 @samp{f95}, @samp{f2003} and @samp{f2008} values specify strict
350 conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards,
351 respectively; errors are given for all extensions beyond the relevant
352 language standard, and warnings are given for the Fortran 77 features
353 that are permitted but obsolescent in later standards.
357 @node Preprocessing Options
358 @section Enable and customize preprocessing
360 @cindex options, preprocessor
363 Preprocessor related options. See section
364 @ref{Preprocessing and conditional compilation} for more detailed
365 information on preprocessing in @command{gfortran}.
372 @cindex preprocessor, enable
373 @cindex preprocessor, disable
374 Enable preprocessing. The preprocessor is automatically invoked if
375 the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR},
376 @file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use
377 this option to manually enable preprocessing of any kind of Fortran file.
379 To disable preprocessing of files with any of the above listed extensions,
380 use the negative form: @option{-nocpp}.
382 The preprocessor is run in traditional mode, be aware that any
383 restrictions of the file-format, e.g. fixed-form line width,
384 apply for preprocessed output as well.
388 @cindex preprocessor, debugging
389 @cindex debugging, preprocessor
390 Instead of the normal output, generate a list of @code{'#define'}
391 directives for all the macros defined during the execution of the
392 preprocessor, including predefined macros. This gives you a way
393 of finding out what is predefined in your version of the preprocessor.
394 Assuming you have no file @file{foo.f90}, the command
396 touch foo.f90; gfortran -cpp -dM foo.f90
398 will show all the predefined macros.
402 @cindex preprocessor, debugging
403 @cindex debugging, preprocessor
404 Like @option{-dM} except in two respects: it does not include the
405 predefined macros, and it outputs both the @code{#define} directives
406 and the result of preprocessing. Both kinds of output go to the
407 standard output file.
411 @cindex preprocessor, debugging
412 @cindex debugging, preprocessor
413 Like @option{-dD}, but emit only the macro names, not their expansions.
417 @cindex preprocessor, debugging
418 @cindex debugging, preprocessor
419 Like @option{dD} except that only macros that are expanded, or whose
420 definedness is tested in preprocessor directives, are output; the
421 output is delayed until the use or test of the macro; and @code{'#undef'}
422 directives are also output for macros tested but undefined at the time.
426 @cindex preprocessor, debugging
427 @cindex debugging, preprocessor
428 Output @code{'#include'} directives in addition to the result
431 @item -fworking-directory
432 @opindex @code{fworking-directory}
433 @cindex preprocessor, working directory
434 Enable generation of linemarkers in the preprocessor output that will
435 let the compiler know the current working directory at the time of
436 preprocessing. When this option is enabled, the preprocessor will emit,
437 after the initial linemarker, a second linemarker with the current
438 working directory followed by two slashes. GCC will use this directory,
439 when it's present in the preprocessed input, as the directory emitted
440 as the current working directory in some debugging information formats.
441 This option is implicitly enabled if debugging information is enabled,
442 but this can be inhibited with the negated form
443 @option{-fno-working-directory}. If the @option{-P} flag is present
444 in the command line, this option has no effect, since no @code{#line}
445 directives are emitted whatsoever.
447 @item -imultilib @var{dir}
448 @opindex @code{imultilib @var{dir}}
449 @cindex preprocessing, include path
450 Use @var{dir} as a subdirectory of the directory containing target-specific
453 @item -iprefix @var{prefix}
454 @opindex @code{iprefix @var{prefix}}
455 @cindex preprocessing, include path
456 Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
457 options. If the @var{prefix} represents a directory, you should include
458 the final @code{'/'}.
460 @item -isysroot @var{dir}
461 @opindex @code{isysroot @var{dir}}
462 @cindex preprocessing, include path
463 This option is like the @option{--sysroot} option, but applies only to
464 header files. See the @option{--sysroot} option for more information.
466 @item -iquote @var{dir}
467 @opindex @code{iquote @var{dir}}
468 @cindex preprocessing, include path
469 Search @var{dir} only for header files requested with @code{#include "file"};
470 they are not searched for @code{#include <file>}, before all directories
471 specified by @option{-I} and before the standard system directories. If
472 @var{dir} begins with @code{=}, then the @code{=} will be replaced by the
473 sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
475 @item -isystem @var{dir}
476 @opindex @code{isystem @var{dir}}
477 @cindex preprocessing, include path
478 Search @var{dir} for header files, after all directories specified by
479 @option{-I} but before the standard system directories. Mark it as a
480 system directory, so that it gets the same special treatment as is
481 applied to the standard system directories. If @var{dir} begins with
482 @code{=}, then the @code{=} will be replaced by the sysroot prefix;
483 see @option{--sysroot} and @option{-isysroot}.
486 @opindex @code{nostdinc}
487 Do not search the standard system directories for header files. Only
488 the directories you have specified with @option{-I} options (and the
489 directory of the current file, if appropriate) are searched.
492 @opindex @code{undef}
493 Do not predefine any system-specific or GCC-specific macros.
494 The standard predefined macros remain defined.
496 @item -A@var{predicate}=@var{answer}
497 @opindex @code{A@var{predicate}=@var{answer}}
498 @cindex preprocessing, assertation
499 Make an assertion with the predicate @var{predicate} and answer @var{answer}.
500 This form is preferred to the older form -A predicate(answer), which is still
501 supported, because it does not use shell special characters.
503 @item -A-@var{predicate}=@var{answer}
504 @opindex @code{A-@var{predicate}=@var{answer}}
505 @cindex preprocessing, assertation
506 Cancel an assertion with the predicate @var{predicate} and answer @var{answer}.
510 @cindex preprocessing, keep comments
511 Do not discard comments. All comments are passed through to the output
512 file, except for comments in processed directives, which are deleted
513 along with the directive.
515 You should be prepared for side effects when using @option{-C}; it causes
516 the preprocessor to treat comments as tokens in their own right. For example,
517 comments appearing at the start of what would be a directive line have the
518 effect of turning that line into an ordinary source line, since the first
519 token on the line is no longer a @code{'#'}.
521 Warning: this currently handles C-Style comments only. The preprocessor
522 does not yet recognize Fortran-style comments.
526 @cindex preprocessing, keep comments
527 Do not discard comments, including during macro expansion. This is like
528 @option{-C}, except that comments contained within macros are also passed
529 through to the output file where the macro is expanded.
531 In addition to the side-effects of the @option{-C} option, the @option{-CC}
532 option causes all C++-style comments inside a macro to be converted to C-style
533 comments. This is to prevent later use of that macro from inadvertently
534 commenting out the remainder of the source line. The @option{-CC} option
535 is generally used to support lint comments.
537 Warning: this currently handles C- and C++-Style comments only. The
538 preprocessor does not yet recognize Fortran-style comments.
541 @opindex @code{D@var{name}}
542 @cindex preprocessing, define macros
543 Predefine name as a macro, with definition @code{1}.
545 @item -D@var{name}=@var{definition}
546 @opindex @code{D@var{name}=@var{definition}}
547 @cindex preprocessing, define macros
548 The contents of @var{definition} are tokenized and processed as if they
549 appeared during translation phase three in a @code{'#define'} directive.
550 In particular, the definition will be truncated by embedded newline
553 If you are invoking the preprocessor from a shell or shell-like program
554 you may need to use the shell's quoting syntax to protect characters such
555 as spaces that have a meaning in the shell syntax.
557 If you wish to define a function-like macro on the command line, write
558 its argument list with surrounding parentheses before the equals sign
559 (if any). Parentheses are meaningful to most shells, so you will need
560 to quote the option. With sh and csh, @code{-D'name(args...)=definition'}
563 @option{-D} and @option{-U} options are processed in the order they are
564 given on the command line. All -imacros file and -include file options
565 are processed after all -D and -U options.
569 Print the name of each header file used, in addition to other normal
570 activities. Each name is indented to show how deep in the @code{'#include'}
575 @cindex preprocessing, no linemarkers
576 Inhibit generation of linemarkers in the output from the preprocessor.
577 This might be useful when running the preprocessor on something that
578 is not C code, and will be sent to a program which might be confused
582 @opindex @code{U@var{name}}
583 @cindex preprocessing, undefine macros
584 Cancel any previous definition of @var{name}, either built in or provided
585 with a @option{-D} option.
589 @node Error and Warning Options
590 @section Options to request or suppress errors and warnings
591 @cindex options, warnings
592 @cindex options, errors
593 @cindex warnings, suppressing
594 @cindex messages, error
595 @cindex messages, warning
596 @cindex suppressing warnings
598 Errors are diagnostic messages that report that the GNU Fortran compiler
599 cannot compile the relevant piece of source code. The compiler will
600 continue to process the program in an attempt to report further errors
601 to aid in debugging, but will not produce any compiled output.
603 Warnings are diagnostic messages that report constructions which
604 are not inherently erroneous but which are risky or suggest there is
605 likely to be a bug in the program. Unless @option{-Werror} is specified,
606 they do not prevent compilation of the program.
608 You can request many specific warnings with options beginning @option{-W},
609 for example @option{-Wimplicit} to request warnings on implicit
610 declarations. Each of these specific warning options also has a
611 negative form beginning @option{-Wno-} to turn off warnings;
612 for example, @option{-Wno-implicit}. This manual lists only one of the
613 two forms, whichever is not the default.
615 These options control the amount and kinds of errors and warnings produced
619 @item -fmax-errors=@var{n}
620 @opindex @code{fmax-errors=}@var{n}
621 @cindex errors, limiting
622 Limits the maximum number of error messages to @var{n}, at which point
623 GNU Fortran bails out rather than attempting to continue processing the
624 source code. If @var{n} is 0, there is no limit on the number of error
628 @opindex @code{fsyntax-only}
629 @cindex syntax checking
630 Check the code for syntax errors, but don't actually compile it. This
631 will generate module files for each module present in the code, but no
635 @opindex @code{pedantic}
636 Issue warnings for uses of extensions to Fortran 95.
637 @option{-pedantic} also applies to C-language constructs where they
638 occur in GNU Fortran source files, such as use of @samp{\e} in a
639 character constant within a directive like @code{#include}.
641 Valid Fortran 95 programs should compile properly with or without
643 However, without this option, certain GNU extensions and traditional
644 Fortran features are supported as well.
645 With this option, many of them are rejected.
647 Some users try to use @option{-pedantic} to check programs for conformance.
648 They soon find that it does not do quite what they want---it finds some
649 nonstandard practices, but not all.
650 However, improvements to GNU Fortran in this area are welcome.
652 This should be used in conjunction with @option{-std=f95},
653 @option{-std=f2003} or @option{-std=f2008}.
655 @item -pedantic-errors
656 @opindex @code{pedantic-errors}
657 Like @option{-pedantic}, except that errors are produced rather than
663 @cindex warnings, all
664 Enables commonly used warning options pertaining to usage that
665 we recommend avoiding and that we believe are easy to avoid.
666 This currently includes @option{-Waliasing},
667 @option{-Wampersand}, @option{-Wsurprising}, @option{-Wintrinsics-std},
668 @option{-Wno-tabs}, @option{-Wintrinsic-shadow} and @option{-Wline-truncation}.
671 @opindex @code{Waliasing}
673 @cindex warnings, aliasing
674 Warn about possible aliasing of dummy arguments. Specifically, it warns
675 if the same actual argument is associated with a dummy argument with
676 @code{INTENT(IN)} and a dummy argument with @code{INTENT(OUT)} in a call
677 with an explicit interface.
679 The following example will trigger the warning.
683 integer, intent(in) :: a
684 integer, intent(out) :: b
693 @opindex @code{Wampersand}
694 @cindex warnings, ampersand
696 Warn about missing ampersand in continued character constants. The warning is
697 given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95},
698 @option{-std=f2003} and @option{-std=f2008}. Note: With no ampersand
699 given in a continued character constant, GNU Fortran assumes continuation
700 at the first non-comment, non-whitespace character after the ampersand
701 that initiated the continuation.
703 @item -Warray-temporaries
704 @opindex @code{Warray-temporaries}
705 @cindex warnings, array temporaries
706 Warn about array temporaries generated by the compiler. The information
707 generated by this warning is sometimes useful in optimization, in order to
708 avoid such temporaries.
710 @item -Wcharacter-truncation
711 @opindex @code{Wcharacter-truncation}
712 @cindex warnings, character truncation
713 Warn when a character assignment will truncate the assigned string.
715 @item -Wline-truncation
716 @opindex @code{Wline-truncation}
717 @cindex warnings, line truncation
718 Warn when a source code line will be truncated.
721 @opindex @code{Wconversion}
722 @cindex warnings, conversion
724 Warn about implicit conversions between different types.
726 @item -Wimplicit-interface
727 @opindex @code{Wimplicit-interface}
728 @cindex warnings, implicit interface
729 Warn if a procedure is called without an explicit interface.
730 Note this only checks that an explicit interface is present. It does not
731 check that the declared interfaces are consistent across program units.
733 @item -Wintrinsics-std
734 @opindex @code{Wintrinsics-std}
735 @cindex warnings, non-standard intrinsics
736 @cindex warnings, intrinsics of other standards
737 Warn if @command{gfortran} finds a procedure named like an intrinsic not
738 available in the currently selected standard (with @option{-std}) and treats
739 it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can
740 be used to never trigger this behaviour and always link to the intrinsic
741 regardless of the selected standard.
744 @opindex @code{Wsurprising}
745 @cindex warnings, suspicious code
746 Produce a warning when ``suspicious'' code constructs are encountered.
747 While technically legal these usually indicate that an error has been made.
749 This currently produces a warning under the following circumstances:
753 An INTEGER SELECT construct has a CASE that can never be matched as its
754 lower value is greater than its upper value.
757 A LOGICAL SELECT construct has three CASE statements.
760 A TRANSFER specifies a source that is shorter than the destination.
763 The type of a function result is declared more than once with the same type. If
764 @option{-pedantic} or standard-conforming mode is enabled, this is an error.
768 @opindex @code{Wtabs}
769 @cindex warnings, tabs
771 By default, tabs are accepted as whitespace, but tabs are not members
772 of the Fortran Character Set. For continuation lines, a tab followed
773 by a digit between 1 and 9 is supported. @option{-Wno-tabs} will cause
774 a warning to be issued if a tab is encountered. Note, @option{-Wno-tabs}
775 is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003},
776 @option{-std=f2008} and @option{-Wall}.
779 @opindex @code{Wunderflow}
780 @cindex warnings, underflow
782 Produce a warning when numerical constant expressions are
783 encountered, which yield an UNDERFLOW during compilation.
785 @item -Wintrinsic-shadow
786 @opindex @code{Wintrinsic-shadow}
787 @cindex warnings, intrinsic
789 Warn if a user-defined procedure or module procedure has the same name as an
790 intrinsic; in this case, an explicit interface or @code{EXTERNAL} or
791 @code{INTRINSIC} declaration might be needed to get calls later resolved to
792 the desired intrinsic/procedure.
794 @item -Wunused-parameter
795 @opindex @code{Wunused-parameter}
796 @cindex warnings, unused parameter
797 @cindex unused parameter
798 Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter},
799 @command{gfortran}'s implementation of this option does not warn
800 about unused dummy arguments, but about unused @code{PARAMETER} values.
801 @option{-Wunused-parameter} is not included in @option{-Wall} but is
802 implied by @option{-Wall -Wextra}.
804 @item -Walign-commons
805 @opindex @code{Walign-commons}
806 @cindex warnings, alignment of COMMON blocks
807 @cindex alignment of COMMON blocks
808 By default, @command{gfortran} warns about any occasion of variables being
809 padded for proper alignment inside a COMMON block. This warning can be turned
810 off via @option{-Wno-align-commons}. See also @option{-falign-commons}.
813 @opindex @code{Werror}
814 @cindex warnings, to errors
815 Turns all warnings into errors.
818 @xref{Error and Warning Options,,Options to Request or Suppress Errors and
819 Warnings, gcc,Using the GNU Compiler Collection (GCC)}, for information on
820 more options offered by the GBE shared by @command{gfortran}, @command{gcc}
821 and other GNU compilers.
823 Some of these have no effect when compiling programs written in Fortran.
825 @node Debugging Options
826 @section Options for debugging your program or GNU Fortran
827 @cindex options, debugging
828 @cindex debugging information options
830 GNU Fortran has various special options that are used for debugging
831 either your program or the GNU Fortran compiler.
834 @item -fdump-parse-tree
835 @opindex @code{fdump-parse-tree}
836 Output the internal parse tree before starting code generation. Only
837 really useful for debugging the GNU Fortran compiler itself.
839 @item -ffpe-trap=@var{list}
840 @opindex @code{ffpe-trap=}@var{list}
841 Specify a list of IEEE exceptions when a Floating Point Exception
842 (FPE) should be raised. On most systems, this will result in a SIGFPE
843 signal being sent and the program being interrupted, producing a core
844 file useful for debugging. @var{list} is a (possibly empty) comma-separated
845 list of the following IEEE exceptions: @samp{invalid} (invalid floating
846 point operation, such as @code{SQRT(-1.0)}), @samp{zero} (division by
847 zero), @samp{overflow} (overflow in a floating point operation),
848 @samp{underflow} (underflow in a floating point operation),
849 @samp{precision} (loss of precision during operation) and @samp{denormal}
850 (operation produced a denormal value).
852 Some of the routines in the Fortran runtime library, like
853 @samp{CPU_TIME}, are likely to to trigger floating point exceptions when
854 @code{ffpe-trap=precision} is used. For this reason, the use of
855 @code{ffpe-trap=precision} is not recommended.
858 @opindex @code{fbacktrace}
861 Specify that, when a runtime error is encountered or a deadly signal is
862 emitted (segmentation fault, illegal instruction, bus error or
863 floating-point exception), the Fortran runtime
864 library should output a backtrace of the error. This option
865 only has influence for compilation of the Fortran main program.
869 @opindex @code{fdump-core}
870 Request that a core-dump file is written to disk when a runtime error
871 is encountered on systems that support core dumps. This option is
872 only effective for the compilation of the Fortran main program.
875 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
876 gcc,Using the GNU Compiler Collection (GCC)}, for more information on
879 @node Directory Options
880 @section Options for directory search
881 @cindex directory, options
882 @cindex options, directory search
884 @cindex INCLUDE directive
885 @cindex directive, INCLUDE
886 These options affect how GNU Fortran searches
887 for files specified by the @code{INCLUDE} directive and where it searches
888 for previously compiled modules.
890 It also affects the search paths used by @command{cpp} when used to preprocess
895 @opindex @code{I}@var{dir}
896 @cindex directory, search paths for inclusion
897 @cindex inclusion, directory search paths for
898 @cindex search paths, for included files
899 @cindex paths, search
900 @cindex module search path
901 These affect interpretation of the @code{INCLUDE} directive
902 (as well as of the @code{#include} directive of the @command{cpp}
905 Also note that the general behavior of @option{-I} and
906 @code{INCLUDE} is pretty much the same as of @option{-I} with
907 @code{#include} in the @command{cpp} preprocessor, with regard to
908 looking for @file{header.gcc} files and other such things.
910 This path is also used to search for @file{.mod} files when previously
911 compiled modules are required by a @code{USE} statement.
913 @xref{Directory Options,,Options for Directory Search,
914 gcc,Using the GNU Compiler Collection (GCC)}, for information on the
919 @opindex @code{J}@var{dir}
920 @opindex @code{M}@var{dir}
921 @cindex paths, search
922 @cindex module search path
923 This option specifies where to put @file{.mod} files for compiled modules.
924 It is also added to the list of directories to searched by an @code{USE}
927 The default is the current directory.
929 @option{-M} is deprecated to avoid conflicts with existing GCC options.
931 @item -fintrinsic-modules-path @var{dir}
932 @opindex @code{fintrinsic-modules-path} @var{dir}
933 @cindex paths, search
934 @cindex module search path
935 This option specifies the location of pre-compiled intrinsic modules, if
936 they are not in the default location expected by the compiler.
940 @section Influencing the linking step
941 @cindex options, linking
942 @cindex linking, static
944 These options come into play when the compiler links object files into an
945 executable output file. They are meaningless if the compiler is not doing
949 @item -static-libgfortran
950 @opindex @code{static-libgfortran}
951 On systems that provide @file{libgfortran} as a shared and a static
952 library, this option forces the use of the static version. If no
953 shared version of @file{libgfortran} was built when the compiler was
954 configured, this option has no effect.
958 @node Runtime Options
959 @section Influencing runtime behavior
960 @cindex options, runtime
962 These options affect the runtime behavior of programs compiled with GNU Fortran.
964 @item -fconvert=@var{conversion}
965 @opindex @code{fconvert=}@var{conversion}
966 Specify the representation of data for unformatted files. Valid
967 values for conversion are: @samp{native}, the default; @samp{swap},
968 swap between big- and little-endian; @samp{big-endian}, use big-endian
969 representation for unformatted files; @samp{little-endian}, use little-endian
970 representation for unformatted files.
972 @emph{This option has an effect only when used in the main program.
973 The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment
974 variable override the default specified by @option{-fconvert}.}
977 @item -fno-range-check
978 @opindex @code{-fno-range-check}
979 Disable range checking of input values during integer @code{READ} operations.
980 For example, GNU Fortran will give an error if an input value is
981 outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}]. In other words,
982 with @code{INTEGER (kind=4) :: i} , attempting to read @math{-2147483648} will
983 give an error unless @option{-fno-range-check} is given.
986 @item -frecord-marker=@var{length}
987 @opindex @code{frecord-marker=}@var{length}
988 Specify the length of record markers for unformatted files.
989 Valid values for @var{length} are 4 and 8. Default is 4.
990 @emph{This is different from previous versions of @command{gfortran}},
991 which specified a default record marker length of 8 on most
992 systems. If you want to read or write files compatible
993 with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}.
995 @item -fmax-subrecord-length=@var{length}
996 @opindex @code{fmax-subrecord-length=}@var{length}
997 Specify the maximum length for a subrecord. The maximum permitted
998 value for length is 2147483639, which is also the default. Only
999 really useful for use by the gfortran testsuite.
1002 @opindex @code{fsign-zero}
1003 When writing zero values, show the negative sign if the sign bit is set.
1004 @code{fno-sign-zero} does not print the negative sign of zero values for
1005 compatibility with F77. Default behavior is to show the negative sign.
1008 @node Code Gen Options
1009 @section Options for code generation conventions
1010 @cindex code generation, conventions
1011 @cindex options, code generation
1012 @cindex options, run-time
1014 These machine-independent options control the interface conventions
1015 used in code generation.
1017 Most of them have both positive and negative forms; the negative form
1018 of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
1019 one of the forms is listed---the one which is not the default. You
1020 can figure out the other form by either removing @option{no-} or adding
1024 @item -fno-automatic
1025 @opindex @code{fno-automatic}
1026 @cindex @code{SAVE} statement
1027 @cindex statement, @code{SAVE}
1028 Treat each program unit (except those marked as RECURSIVE) as if the
1029 @code{SAVE} statement were specified for every local variable and array
1030 referenced in it. Does not affect common blocks. (Some Fortran compilers
1031 provide this option under the name @option{-static} or @option{-save}.)
1032 The default, which is @option{-fautomatic}, uses the stack for local
1033 variables smaller than the value given by @option{-fmax-stack-var-size}.
1034 Use the option @option{-frecursive} to use no static memory.
1038 @cindex calling convention
1039 @cindex @command{f2c} calling convention
1040 @cindex @command{g77} calling convention
1041 @cindex libf2c calling convention
1042 Generate code designed to be compatible with code generated
1043 by @command{g77} and @command{f2c}.
1045 The calling conventions used by @command{g77} (originally implemented
1046 in @command{f2c}) require functions that return type
1047 default @code{REAL} to actually return the C type @code{double}, and
1048 functions that return type @code{COMPLEX} to return the values via an
1049 extra argument in the calling sequence that points to where to
1050 store the return value. Under the default GNU calling conventions, such
1051 functions simply return their results as they would in GNU
1052 C---default @code{REAL} functions return the C type @code{float}, and
1053 @code{COMPLEX} functions return the GNU C type @code{complex}.
1054 Additionally, this option implies the @option{-fsecond-underscore}
1055 option, unless @option{-fno-second-underscore} is explicitly requested.
1057 This does not affect the generation of code that interfaces with
1058 the @command{libgfortran} library.
1060 @emph{Caution:} It is not a good idea to mix Fortran code compiled with
1061 @option{-ff2c} with code compiled with the default @option{-fno-f2c}
1062 calling conventions as, calling @code{COMPLEX} or default @code{REAL}
1063 functions between program parts which were compiled with different
1064 calling conventions will break at execution time.
1066 @emph{Caution:} This will break code which passes intrinsic functions
1067 of type default @code{REAL} or @code{COMPLEX} as actual arguments, as
1068 the library implementations use the @option{-fno-f2c} calling conventions.
1070 @item -fno-underscoring
1071 @opindex @code{fno-underscoring}
1073 @cindex symbol names, underscores
1074 @cindex transforming symbol names
1075 @cindex symbol names, transforming
1076 Do not transform names of entities specified in the Fortran
1077 source file by appending underscores to them.
1079 With @option{-funderscoring} in effect, GNU Fortran appends one
1080 underscore to external names with no underscores. This is done to ensure
1081 compatibility with code produced by many UNIX Fortran compilers.
1083 @emph{Caution}: The default behavior of GNU Fortran is
1084 incompatible with @command{f2c} and @command{g77}, please use the
1085 @option{-ff2c} option if you want object files compiled with
1086 GNU Fortran to be compatible with object code created with these
1089 Use of @option{-fno-underscoring} is not recommended unless you are
1090 experimenting with issues such as integration of GNU Fortran into
1091 existing system environments (vis-@`{a}-vis existing libraries, tools,
1094 For example, with @option{-funderscoring}, and assuming other defaults like
1095 @option{-fcase-lower} and that @code{j()} and @code{max_count()} are
1096 external functions while @code{my_var} and @code{lvar} are local variables,
1099 I = J() + MAX_COUNT (MY_VAR, LVAR)
1102 is implemented as something akin to:
1104 i = j_() + max_count__(&my_var__, &lvar);
1107 With @option{-fno-underscoring}, the same statement is implemented as:
1110 i = j() + max_count(&my_var, &lvar);
1113 Use of @option{-fno-underscoring} allows direct specification of
1114 user-defined names while debugging and when interfacing GNU Fortran
1115 code with other languages.
1117 Note that just because the names match does @emph{not} mean that the
1118 interface implemented by GNU Fortran for an external name matches the
1119 interface implemented by some other language for that same name.
1120 That is, getting code produced by GNU Fortran to link to code produced
1121 by some other compiler using this or any other method can be only a
1122 small part of the overall solution---getting the code generated by
1123 both compilers to agree on issues other than naming can require
1124 significant effort, and, unlike naming disagreements, linkers normally
1125 cannot detect disagreements in these other areas.
1127 Also, note that with @option{-fno-underscoring}, the lack of appended
1128 underscores introduces the very real possibility that a user-defined
1129 external name will conflict with a name in a system library, which
1130 could make finding unresolved-reference bugs quite difficult in some
1131 cases---they might occur at program run time, and show up only as
1132 buggy behavior at run time.
1134 In future versions of GNU Fortran we hope to improve naming and linking
1135 issues so that debugging always involves using the names as they appear
1136 in the source, even if the names as seen by the linker are mangled to
1137 prevent accidental linking between procedures with incompatible
1140 @item -fsecond-underscore
1141 @opindex @code{fsecond-underscore}
1143 @cindex symbol names, underscores
1144 @cindex transforming symbol names
1145 @cindex symbol names, transforming
1146 @cindex @command{f2c} calling convention
1147 @cindex @command{g77} calling convention
1148 @cindex libf2c calling convention
1149 By default, GNU Fortran appends an underscore to external
1150 names. If this option is used GNU Fortran appends two
1151 underscores to names with underscores and one underscore to external names
1152 with no underscores. GNU Fortran also appends two underscores to
1153 internal names with underscores to avoid naming collisions with external
1156 This option has no effect if @option{-fno-underscoring} is
1157 in effect. It is implied by the @option{-ff2c} option.
1159 Otherwise, with this option, an external name such as @code{MAX_COUNT}
1160 is implemented as a reference to the link-time external symbol
1161 @code{max_count__}, instead of @code{max_count_}. This is required
1162 for compatibility with @command{g77} and @command{f2c}, and is implied
1163 by use of the @option{-ff2c} option.
1165 @item -fbounds-check
1166 @opindex @code{fbounds-check}
1167 @cindex array, bounds checking
1168 @cindex bounds checking
1169 @cindex range checking
1170 @cindex subscript checking
1171 @cindex checking subscripts
1172 Enable generation of run-time checks for array subscripts
1173 and against the declared minimum and maximum values. It also
1174 checks array indices for assumed and deferred
1175 shape arrays against the actual allocated bounds.
1177 Some checks require that @option{-fbounds-check} is set for
1178 the compilation of the main program.
1180 In the future this may also include other forms of checking, e.g., checking
1181 substring references.
1184 @item fcheck-array-temporaries
1185 @opindex @code{fcheck-array-temporaries}
1186 @cindex checking array temporaries
1187 Warns at run time when for passing an actual argument a temporary array
1188 had to be generated. The information generated by this warning is
1189 sometimes useful in optimization, in order to avoid such temporaries.
1191 Note: The warning is only printed once per location.
1194 @item -fmax-stack-var-size=@var{n}
1195 @opindex @code{fmax-stack-var-size}
1196 This option specifies the size in bytes of the largest array that will be put
1197 on the stack; if the size is exceeded static memory is used (except in
1198 procedures marked as RECURSIVE). Use the option @option{-frecursive} to
1199 allow for recursive procedures which do not have a RECURSIVE attribute or
1200 for parallel programs. Use @option{-fno-automatic} to never use the stack.
1202 This option currently only affects local arrays declared with constant
1203 bounds, and may not apply to all character variables.
1204 Future versions of GNU Fortran may improve this behavior.
1206 The default value for @var{n} is 32768.
1208 @item -fpack-derived
1209 @opindex @code{fpack-derived}
1210 @cindex structure packing
1211 This option tells GNU Fortran to pack derived type members as closely as
1212 possible. Code compiled with this option is likely to be incompatible
1213 with code compiled without this option, and may execute slower.
1215 @item -frepack-arrays
1216 @opindex @code{frepack-arrays}
1217 @cindex repacking arrays
1218 In some circumstances GNU Fortran may pass assumed shape array
1219 sections via a descriptor describing a noncontiguous area of memory.
1220 This option adds code to the function prologue to repack the data into
1221 a contiguous block at runtime.
1223 This should result in faster accesses to the array. However it can introduce
1224 significant overhead to the function call, especially when the passed data
1228 @opindex @code{fshort-enums}
1229 This option is provided for interoperability with C code that was
1230 compiled with the @option{-fshort-enums} option. It will make
1231 GNU Fortran choose the smallest @code{INTEGER} kind a given
1232 enumerator set will fit in, and give all its enumerators this kind.
1234 @item -fexternal-blas
1235 @opindex @code{fexternal-blas}
1236 This option will make @command{gfortran} generate calls to BLAS functions
1237 for some matrix operations like @code{MATMUL}, instead of using our own
1238 algorithms, if the size of the matrices involved is larger than a given
1239 limit (see @option{-fblas-matmul-limit}). This may be profitable if an
1240 optimized vendor BLAS library is available. The BLAS library will have
1241 to be specified at link time.
1243 @item -fblas-matmul-limit=@var{n}
1244 @opindex @code{fblas-matmul-limit}
1245 Only significant when @option{-fexternal-blas} is in effect.
1246 Matrix multiplication of matrices with size larger than (or equal to) @var{n}
1247 will be performed by calls to BLAS functions, while others will be
1248 handled by @command{gfortran} internal algorithms. If the matrices
1249 involved are not square, the size comparison is performed using the
1250 geometric mean of the dimensions of the argument and result matrices.
1252 The default value for @var{n} is 30.
1255 @opindex @code{frecursive}
1256 Allow indirect recursion by forcing all local arrays to be allocated
1257 on the stack. This flag cannot be used together with
1258 @option{-fmax-stack-var-size=} or @option{-fno-automatic}.
1260 @item -finit-local-zero
1261 @item -finit-integer=@var{n}
1262 @item -finit-real=@var{<zero|inf|-inf|nan>}
1263 @item -finit-logical=@var{<true|false>}
1264 @item -finit-character=@var{n}
1265 @opindex @code{finit-local-zero}
1266 @opindex @code{finit-integer}
1267 @opindex @code{finit-real}
1268 @opindex @code{finit-logical}
1269 @opindex @code{finit-character}
1270 The @option{-finit-local-zero} option instructs the compiler to
1271 initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX}
1272 variables to zero, @code{LOGICAL} variables to false, and
1273 @code{CHARACTER} variables to a string of null bytes. Finer-grained
1274 initialization options are provided by the
1275 @option{-finit-integer=@var{n}},
1276 @option{-finit-real=@var{<zero|inf|-inf|nan>}} (which also initializes
1277 the real and imaginary parts of local @code{COMPLEX} variables),
1278 @option{-finit-logical=@var{<true|false>}}, and
1279 @option{-finit-character=@var{n}} (where @var{n} is an ASCII character
1280 value) options. These options do not initialize components of derived
1281 type variables, nor do they initialize variables that appear in an
1282 @code{EQUIVALENCE} statement. (This limitation may be removed in
1285 Note that the @option{-finit-real=nan} option initializes @code{REAL}
1286 and @code{COMPLEX} variables with a quiet NaN.
1288 @item -falign-commons
1289 @opindex @code{falign-commons}
1290 @cindex alignment of COMMON blocks
1291 By default, @command{gfortran} enforces proper alignment of all variables in a
1292 COMMON block by padding them as needed. On certain platforms this is mandatory,
1293 on others it increases performance. If a COMMON block is not declared with
1294 consistent data types everywhere, this padding can cause trouble, and
1295 @option{-fno-align-commons } can be used to disable automatic alignment. The
1296 same form of this option should be used for all files that share a COMMON block.
1297 To avoid potential alignment issues in COMMON blocks, it is recommended to order
1298 objects from largests to smallest.
1301 @xref{Code Gen Options,,Options for Code Generation Conventions,
1302 gcc,Using the GNU Compiler Collection (GCC)}, for information on more options
1304 shared by @command{gfortran}, @command{gcc}, and other GNU compilers.
1309 @node Environment Variables
1310 @section Environment variables affecting @command{gfortran}
1311 @cindex environment variable
1313 @c man begin ENVIRONMENT
1315 The @command{gfortran} compiler currently does not make use of any environment
1316 variables to control its operation above and beyond those
1317 that affect the operation of @command{gcc}.
1319 @xref{Environment Variables,,Environment Variables Affecting GCC,
1320 gcc,Using the GNU Compiler Collection (GCC)}, for information on environment
1323 @xref{Runtime}, for environment variables that affect the
1324 run-time behavior of programs compiled with GNU Fortran.