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d3d3011f | 1 | @c Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 |
6de9cd9a | 2 | @c Free Software Foundation, Inc. |
7fc15ba5 | 3 | @c This is part of the GNU Fortran manual. |
6de9cd9a DN |
4 | @c For copying conditions, see the file gfortran.texi. |
5 | ||
6 | @ignore | |
7 | @c man begin COPYRIGHT | |
33abc845 | 8 | Copyright @copyright{} 2004, 2005, 2006, 2007, 2008, 2009 |
6de9cd9a DN |
9 | Free Software Foundation, Inc. |
10 | ||
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 | |
70b1e376 RW |
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. | |
6ccde948 | 17 | |
6de9cd9a DN |
18 | (a) The FSF's Front-Cover Text is: |
19 | ||
20 | A GNU Manual | |
21 | ||
22 | (b) The FSF's Back-Cover Text is: | |
23 | ||
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. | |
27 | @c man end | |
28 | @c Set file name and title for the man page. | |
29 | @setfilename gfortran | |
7fc15ba5 | 30 | @settitle GNU Fortran compiler. |
6de9cd9a DN |
31 | @c man begin SYNOPSIS |
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{}] | |
6ccde948 | 38 | [@option{-m}@var{machine-option}@dots{}] |
6de9cd9a DN |
39 | [@option{-o} @var{outfile}] @var{infile}@dots{} |
40 | ||
41 | Only the most useful options are listed here; see below for the | |
42 | remainder. | |
43 | @c man end | |
44 | @c man begin SEEALSO | |
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}. | |
49 | @c man end | |
50 | @c man begin BUGS | |
51 | For instructions on reporting bugs, see | |
2f41c1d6 | 52 | @w{@value{BUGURL}}. |
6de9cd9a DN |
53 | @c man end |
54 | @c man begin AUTHOR | |
55 | See the Info entry for @command{gfortran} for contributors to GCC and | |
7fc15ba5 | 56 | GNU Fortran. |
6de9cd9a DN |
57 | @c man end |
58 | @end ignore | |
59 | ||
7fc15ba5 BM |
60 | @node Invoking GNU Fortran |
61 | @chapter GNU Fortran Command Options | |
62 | @cindex GNU Fortran command options | |
6de9cd9a | 63 | @cindex command options |
7fc15ba5 | 64 | @cindex options, @command{gfortran} command |
6de9cd9a DN |
65 | |
66 | @c man begin DESCRIPTION | |
67 | ||
68 | The @command{gfortran} command supports all the options supported by the | |
7fc15ba5 | 69 | @command{gcc} command. Only options specific to GNU Fortran are documented here. |
6de9cd9a DN |
70 | |
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). | |
75 | ||
76 | @cindex options, negative forms | |
7fc15ba5 | 77 | All GCC and GNU Fortran options |
6de9cd9a DN |
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++}), | |
7fc15ba5 BM |
81 | since adding GNU Fortran to the GCC distribution |
82 | enables acceptance of GNU Fortran options | |
6de9cd9a DN |
83 | by all of the relevant drivers. |
84 | ||
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. | |
89 | @c man end | |
90 | ||
91 | @menu | |
92 | * Option Summary:: Brief list of all @command{gfortran} options, | |
93 | without explanations. | |
94 | * Fortran Dialect Options:: Controlling the variant of Fortran language | |
95 | compiled. | |
670637ee | 96 | * Preprocessing Options:: Enable and customize preprocessing. |
592600ce | 97 | * Error and Warning Options:: How picky should the compiler be? |
6de9cd9a DN |
98 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. |
99 | * Directory Options:: Where to find module files | |
70263321 | 100 | * Link Options :: Influencing the linking step |
eaa90d25 | 101 | * Runtime Options:: Influencing runtime behavior |
6de9cd9a DN |
102 | * Code Gen Options:: Specifying conventions for function calls, data layout |
103 | and register usage. | |
a2bef74c | 104 | * Environment Variables:: Environment variables that affect @command{gfortran}. |
6de9cd9a DN |
105 | @end menu |
106 | ||
107 | @node Option Summary | |
a2bef74c | 108 | @section Option summary |
6de9cd9a DN |
109 | |
110 | @c man begin OPTIONS | |
111 | ||
112 | Here is a summary of all the options specific to GNU Fortran, grouped | |
113 | by type. Explanations are in the following sections. | |
114 | ||
115 | @table @emph | |
116 | @item Fortran Language Options | |
a2bef74c | 117 | @xref{Fortran Dialect Options,,Options controlling Fortran dialect}. |
592600ce | 118 | @gccoptlist{-fall-intrinsics -ffree-form -fno-fixed-form @gol |
6de9cd9a | 119 | -fdollar-ok -fimplicit-none -fmax-identifier-length @gol |
592600ce | 120 | -std=@var{std} -fd-lines-as-code -fd-lines-as-comments @gol |
6de9cd9a | 121 | -ffixed-line-length-@var{n} -ffixed-line-length-none @gol |
16ab8e74 | 122 | -ffree-line-length-@var{n} -ffree-line-length-none @gol |
83d890b9 | 123 | -fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol |
4e6bf178 | 124 | -fcray-pointer -fopenmp -fno-range-check -fbackslash -fmodule-private} |
6de9cd9a | 125 | |
670637ee DF |
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} | |
133 | ||
592600ce | 134 | @item Error and Warning Options |
a2bef74c DF |
135 | @xref{Error and Warning Options,,Options to request or suppress errors |
136 | and warnings}. | |
592600ce | 137 | @gccoptlist{-fmax-errors=@var{n} @gol |
6de9cd9a | 138 | -fsyntax-only -pedantic -pedantic-errors @gol |
bdfd2ff0 | 139 | -Wall -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol |
ca071303 FXC |
140 | -Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation @gol |
141 | -Wintrinsics-std -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter @gol | |
142 | -Wintrinsics-shadow -Wno-align-commons} | |
6de9cd9a DN |
143 | |
144 | @item Debugging Options | |
a2bef74c | 145 | @xref{Debugging Options,,Options for debugging your program or GNU Fortran}. |
868d75db FXC |
146 | @gccoptlist{-fdump-parse-tree -ffpe-trap=@var{list} @gol |
147 | -fdump-core -fbacktrace} | |
6de9cd9a DN |
148 | |
149 | @item Directory Options | |
a2bef74c | 150 | @xref{Directory Options,,Options for directory search}. |
63346ddb SK |
151 | @gccoptlist{-I@var{dir} -J@var{dir} -M@var{dir} @gol |
152 | -fintrinsic-modules-path @var{dir}} | |
6de9cd9a | 153 | |
70263321 DF |
154 | @item Link Options |
155 | @xref{Link Options,,Options for influencing the linking step}. | |
156 | @gccoptlist{-static-libgfortran} | |
157 | ||
eaa90d25 TK |
158 | @item Runtime Options |
159 | @xref{Runtime Options,,Options for influencing runtime behavior}. | |
082b0571 JD |
160 | @gccoptlist{-fconvert=@var{conversion} -fno-range-check |
161 | -frecord-marker=@var{length} @gol -fmax-subrecord-length=@var{length} | |
162 | -fsign-zero} | |
eaa90d25 | 163 | |
6de9cd9a | 164 | @item Code Generation Options |
a2bef74c | 165 | @xref{Code Gen Options,,Options for code generation conventions}. |
63346ddb | 166 | @gccoptlist{-fno-automatic -ff2c -fno-underscoring @gol |
71a7778c | 167 | -fwhole-file -fsecond-underscore @gol |
63346ddb | 168 | -fbounds-check -fcheck-array-temporaries -fmax-array-constructor =@var{n} @gol |
22bdbb0f | 169 | -fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} |
63346ddb | 170 | -fmax-stack-var-size=@var{n} @gol |
592600ce | 171 | -fpack-derived -frepack-arrays -fshort-enums -fexternal-blas @gol |
51b09ce3 | 172 | -fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol |
346a77d1 | 173 | -finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan|snan>} @gol |
f613cea7 | 174 | -finit-logical=@var{<true|false>} -finit-character=@var{n} -fno-align-commons} |
6de9cd9a DN |
175 | @end table |
176 | ||
6de9cd9a DN |
177 | @menu |
178 | * Fortran Dialect Options:: Controlling the variant of Fortran language | |
179 | compiled. | |
670637ee | 180 | * Preprocessing Options:: Enable and customize preprocessing. |
592600ce | 181 | * Error and Warning Options:: How picky should the compiler be? |
6de9cd9a DN |
182 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. |
183 | * Directory Options:: Where to find module files | |
70263321 | 184 | * Link Options :: Influencing the linking step |
eaa90d25 | 185 | * Runtime Options:: Influencing runtime behavior |
6de9cd9a DN |
186 | * Code Gen Options:: Specifying conventions for function calls, data layout |
187 | and register usage. | |
188 | @end menu | |
189 | ||
190 | @node Fortran Dialect Options | |
a2bef74c | 191 | @section Options controlling Fortran dialect |
6de9cd9a DN |
192 | @cindex dialect options |
193 | @cindex language, dialect options | |
194 | @cindex options, dialect | |
195 | ||
3397327c BM |
196 | The following options control the details of the Fortran dialect |
197 | accepted by the compiler: | |
6de9cd9a DN |
198 | |
199 | @table @gcctabopt | |
4ba96c02 BM |
200 | @item -ffree-form |
201 | @item -ffixed-form | |
32864778 DF |
202 | @opindex @code{ffree-form} |
203 | @opindex @code{fno-fixed-form} | |
204 | @cindex options, fortran dialect | |
e739dfac DF |
205 | @cindex file format, free |
206 | @cindex file format, fixed | |
49de9e73 | 207 | Specify the layout used by the source file. The free form layout |
6de9cd9a | 208 | was introduced in Fortran 90. Fixed form was traditionally used in |
3397327c BM |
209 | older Fortran programs. When neither option is specified, the source |
210 | form is determined by the file extension. | |
6de9cd9a | 211 | |
a23eec13 | 212 | @item -fall-intrinsics |
32864778 | 213 | @opindex @code{fall-intrinsics} |
aad9c4f4 AM |
214 | This option causes all intrinsic procedures (including the GNU-specific |
215 | extensions) to be accepted. This can be useful with @option{-std=f95} to | |
216 | force standard-compliance but get access to the full range of intrinsics | |
217 | available with @command{gfortran}. As a consequence, @option{-Wintrinsics-std} | |
218 | will be ignored and no user-defined procedure with the same name as any | |
219 | intrinsic will be called except when it is explicitly declared @code{EXTERNAL}. | |
a23eec13 | 220 | |
e0bcf78c | 221 | @item -fd-lines-as-code |
259b41c1 | 222 | @item -fd-lines-as-comments |
32864778 DF |
223 | @opindex @code{fd-lines-as-code} |
224 | @opindex @code{fd-lines-as-comments} | |
4ba96c02 | 225 | Enable special treatment for lines beginning with @code{d} or @code{D} |
3397327c BM |
226 | in fixed form sources. If the @option{-fd-lines-as-code} option is |
227 | given they are treated as if the first column contained a blank. If the | |
e0bcf78c TS |
228 | @option{-fd-lines-as-comments} option is given, they are treated as |
229 | comment lines. | |
230 | ||
3ae9eb27 | 231 | @item -fdefault-double-8 |
32864778 | 232 | @opindex @code{fdefault-double-8} |
aad9c4f4 AM |
233 | Set the @code{DOUBLE PRECISION} type to an 8 byte wide type. If |
234 | @option{-fdefault-real-8} is given, @code{DOUBLE PRECISION} would | |
235 | instead be promoted to 16 bytes if possible, and @option{-fdefault-double-8} | |
236 | can be used to prevent this. The kind of real constants like @code{1.d0} will | |
237 | not be changed by @option{-fdefault-real-8} though, so also | |
238 | @option{-fdefault-double-8} does not affect it. | |
3ae9eb27 | 239 | |
3ae9eb27 | 240 | @item -fdefault-integer-8 |
32864778 | 241 | @opindex @code{fdefault-integer-8} |
3ae9eb27 | 242 | Set the default integer and logical types to an 8 byte wide type. |
aad9c4f4 AM |
243 | Do nothing if this is already the default. This option also affects |
244 | the kind of integer constants like @code{42}. | |
3ae9eb27 | 245 | |
3ae9eb27 | 246 | @item -fdefault-real-8 |
32864778 | 247 | @opindex @code{fdefault-real-8} |
3ae9eb27 | 248 | Set the default real type to an 8 byte wide type. |
aad9c4f4 AM |
249 | Do nothing if this is already the default. This option also affects |
250 | the kind of non-double real constants like @code{1.0}, and does promote | |
251 | the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless | |
252 | @code{-fdefault-double-8} is given, too. | |
3ae9eb27 | 253 | |
6de9cd9a | 254 | @item -fdollar-ok |
32864778 | 255 | @opindex @code{fdollar-ok} |
e739dfac | 256 | @cindex $ |
6de9cd9a DN |
257 | @cindex symbol names |
258 | @cindex character set | |
f4a55802 DF |
259 | Allow @samp{$} as a valid non-first character in a symbol name. Symbols |
260 | that start with @samp{$} are rejected since it is unclear which rules to | |
cba2a54e | 261 | apply to implicit typing as different vendors implement different rules. |
6e8cb9be | 262 | Using @samp{$} in @code{IMPLICIT} statements is also rejected. |
6de9cd9a | 263 | |
4e6bf178 TB |
264 | @item -fbackslash |
265 | @opindex @code{backslash} | |
131c66cd FXC |
266 | @cindex backslash |
267 | @cindex escape characters | |
8fc541d3 FXC |
268 | Change the interpretation of backslashes in string literals from a single |
269 | backslash character to ``C-style'' escape characters. The following | |
270 | combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n}, | |
271 | @code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII | |
272 | characters alert, backspace, form feed, newline, carriage return, | |
273 | horizontal tab, vertical tab, backslash, and NUL, respectively. | |
274 | Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and | |
275 | @code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are | |
276 | translated into the Unicode characters corresponding to the specified code | |
277 | points. All other combinations of a character preceded by \ are | |
278 | unexpanded. | |
131c66cd | 279 | |
654b6073 FXC |
280 | @item -fmodule-private |
281 | @opindex @code{fmodule-private} | |
282 | @cindex module entities | |
283 | @cindex private | |
284 | Set the default accessibility of module entities to @code{PRIVATE}. | |
285 | Use-associated entities will not be accessible unless they are explicitly | |
286 | declared as @code{PUBLIC}. | |
287 | ||
6de9cd9a | 288 | @item -ffixed-line-length-@var{n} |
32864778 | 289 | @opindex @code{ffixed-line-length-}@var{n} |
e739dfac | 290 | @cindex file format, fixed |
6de9cd9a DN |
291 | Set column after which characters are ignored in typical fixed-form |
292 | lines in the source file, and through which spaces are assumed (as | |
293 | if padded to that length) after the ends of short fixed-form lines. | |
294 | ||
6de9cd9a | 295 | Popular values for @var{n} include 72 (the |
3397327c | 296 | standard and the default), 80 (card image), and 132 (corresponding |
6de9cd9a | 297 | to ``extended-source'' options in some popular compilers). |
3397327c | 298 | @var{n} may also be @samp{none}, meaning that the entire line is meaningful |
6de9cd9a DN |
299 | and that continued character constants never have implicit spaces appended |
300 | to them to fill out the line. | |
301 | @option{-ffixed-line-length-0} means the same thing as | |
302 | @option{-ffixed-line-length-none}. | |
303 | ||
16ab8e74 | 304 | @item -ffree-line-length-@var{n} |
32864778 | 305 | @opindex @code{ffree-line-length-}@var{n} |
e739dfac | 306 | @cindex file format, free |
16ab8e74 | 307 | Set column after which characters are ignored in typical free-form |
3397327c | 308 | lines in the source file. The default value is 132. |
16ab8e74 BF |
309 | @var{n} may be @samp{none}, meaning that the entire line is meaningful. |
310 | @option{-ffree-line-length-0} means the same thing as | |
311 | @option{-ffree-line-length-none}. | |
312 | ||
6de9cd9a | 313 | @item -fmax-identifier-length=@var{n} |
32864778 | 314 | @opindex @code{fmax-identifier-length=}@var{n} |
6de9cd9a | 315 | Specify the maximum allowed identifier length. Typical values are |
f489fba1 | 316 | 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008). |
6de9cd9a | 317 | |
6de9cd9a | 318 | @item -fimplicit-none |
32864778 | 319 | @opindex @code{fimplicit-none} |
6de9cd9a | 320 | Specify that no implicit typing is allowed, unless overridden by explicit |
40746dcc BM |
321 | @code{IMPLICIT} statements. This is the equivalent of adding |
322 | @code{implicit none} to the start of every procedure. | |
6de9cd9a | 323 | |
83d890b9 | 324 | @item -fcray-pointer |
32864778 | 325 | @opindex @code{fcray-pointer} |
3397327c BM |
326 | Enable the Cray pointer extension, which provides C-like pointer |
327 | functionality. | |
83d890b9 | 328 | |
6c7a4dfd | 329 | @item -fopenmp |
32864778 | 330 | @opindex @code{fopenmp} |
4e8b3590 | 331 | @cindex OpenMP |
3397327c BM |
332 | Enable the OpenMP extensions. This includes OpenMP @code{!$omp} directives |
333 | in free form | |
6c7a4dfd | 334 | and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form, |
3397327c BM |
335 | @code{!$} conditional compilation sentinels in free form |
336 | and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form, | |
6c7a4dfd | 337 | and when linking arranges for the OpenMP runtime library to be linked |
1e7de83b | 338 | in. The option @option{-fopenmp} implies @option{-frecursive}. |
6c7a4dfd | 339 | |
200c5036 | 340 | @item -fno-range-check |
32864778 | 341 | @opindex @code{frange-check} |
200c5036 | 342 | Disable range checking on results of simplification of constant |
a84b9ee8 SK |
343 | expressions during compilation. For example, GNU Fortran will give |
344 | an error at compile time when simplifying @code{a = 1. / 0}. | |
345 | With this option, no error will be given and @code{a} will be assigned | |
346 | the value @code{+Infinity}. If an expression evaluates to a value | |
347 | outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}], | |
348 | then the expression will be replaced by @code{-Inf} or @code{+Inf} | |
349 | as appropriate. | |
40746dcc BM |
350 | Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow |
351 | on most systems, but with @option{-fno-range-check} the value will | |
352 | ``wrap around'' and @code{i} will be initialized to @math{-1} instead. | |
54554825 | 353 | |
6de9cd9a | 354 | @item -std=@var{std} |
32864778 | 355 | @opindex @code{std=}@var{std} option |
276419d0 | 356 | Specify the standard to which the program is expected to conform, which |
f489fba1 FXC |
357 | may be one of @samp{f95}, @samp{f2003}, @samp{f2008}, @samp{gnu}, or |
358 | @samp{legacy}. The default value for @var{std} is @samp{gnu}, which | |
359 | specifies a superset of the Fortran 95 standard that includes all of the | |
360 | extensions supported by GNU Fortran, although warnings will be given for | |
361 | obsolete extensions not recommended for use in new code. The | |
362 | @samp{legacy} value is equivalent but without the warnings for obsolete | |
363 | extensions, and may be useful for old non-standard programs. The | |
364 | @samp{f95}, @samp{f2003} and @samp{f2008} values specify strict | |
365 | conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards, | |
366 | respectively; errors are given for all extensions beyond the relevant | |
367 | language standard, and warnings are given for the Fortran 77 features | |
368 | that are permitted but obsolescent in later standards. | |
6de9cd9a | 369 | |
6de9cd9a DN |
370 | @end table |
371 | ||
670637ee DF |
372 | @node Preprocessing Options |
373 | @section Enable and customize preprocessing | |
374 | @cindex preprocessor | |
375 | @cindex options, preprocessor | |
376 | @cindex CPP | |
377 | ||
378 | Preprocessor related options. See section | |
379 | @ref{Preprocessing and conditional compilation} for more detailed | |
380 | information on preprocessing in @command{gfortran}. | |
381 | ||
382 | @table @gcctabopt | |
383 | @item -cpp | |
384 | @item -nocpp | |
385 | @opindex @code{cpp} | |
386 | @opindex @code{fpp} | |
387 | @cindex preprocessor, enable | |
388 | @cindex preprocessor, disable | |
389 | Enable preprocessing. The preprocessor is automatically invoked if | |
390 | the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR}, | |
391 | @file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use | |
392 | this option to manually enable preprocessing of any kind of Fortran file. | |
393 | ||
394 | To disable preprocessing of files with any of the above listed extensions, | |
395 | use the negative form: @option{-nocpp}. | |
396 | ||
397 | The preprocessor is run in traditional mode, be aware that any | |
398 | restrictions of the file-format, e.g. fixed-form line width, | |
399 | apply for preprocessed output as well. | |
400 | ||
401 | @item -dM | |
402 | @opindex @code{dM} | |
403 | @cindex preprocessor, debugging | |
404 | @cindex debugging, preprocessor | |
405 | Instead of the normal output, generate a list of @code{'#define'} | |
406 | directives for all the macros defined during the execution of the | |
407 | preprocessor, including predefined macros. This gives you a way | |
408 | of finding out what is predefined in your version of the preprocessor. | |
409 | Assuming you have no file @file{foo.f90}, the command | |
410 | @smallexample | |
411 | touch foo.f90; gfortran -cpp -dM foo.f90 | |
412 | @end smallexample | |
413 | will show all the predefined macros. | |
414 | ||
415 | @item -dD | |
416 | @opindex @code{dD} | |
417 | @cindex preprocessor, debugging | |
418 | @cindex debugging, preprocessor | |
419 | Like @option{-dM} except in two respects: it does not include the | |
420 | predefined macros, and it outputs both the @code{#define} directives | |
421 | and the result of preprocessing. Both kinds of output go to the | |
422 | standard output file. | |
423 | ||
424 | @item -dN | |
425 | @opindex @code{dN} | |
426 | @cindex preprocessor, debugging | |
427 | @cindex debugging, preprocessor | |
428 | Like @option{-dD}, but emit only the macro names, not their expansions. | |
429 | ||
430 | @item -dU | |
431 | @opindex @code{dU} | |
432 | @cindex preprocessor, debugging | |
433 | @cindex debugging, preprocessor | |
434 | Like @option{dD} except that only macros that are expanded, or whose | |
435 | definedness is tested in preprocessor directives, are output; the | |
436 | output is delayed until the use or test of the macro; and @code{'#undef'} | |
437 | directives are also output for macros tested but undefined at the time. | |
438 | ||
439 | @item -dI | |
440 | @opindex @code{dI} | |
441 | @cindex preprocessor, debugging | |
442 | @cindex debugging, preprocessor | |
443 | Output @code{'#include'} directives in addition to the result | |
444 | of preprocessing. | |
445 | ||
446 | @item -fworking-directory | |
447 | @opindex @code{fworking-directory} | |
448 | @cindex preprocessor, working directory | |
449 | Enable generation of linemarkers in the preprocessor output that will | |
450 | let the compiler know the current working directory at the time of | |
451 | preprocessing. When this option is enabled, the preprocessor will emit, | |
452 | after the initial linemarker, a second linemarker with the current | |
453 | working directory followed by two slashes. GCC will use this directory, | |
454 | when it's present in the preprocessed input, as the directory emitted | |
455 | as the current working directory in some debugging information formats. | |
456 | This option is implicitly enabled if debugging information is enabled, | |
457 | but this can be inhibited with the negated form | |
458 | @option{-fno-working-directory}. If the @option{-P} flag is present | |
459 | in the command line, this option has no effect, since no @code{#line} | |
460 | directives are emitted whatsoever. | |
461 | ||
c3280643 DF |
462 | @item -idirafter @var{dir} |
463 | @opindex @code{idirafter @var{dir}} | |
464 | @cindex preprocessing, include path | |
465 | Search @var{dir} for include files, but do it after all directories | |
466 | specified with @option{-I} and the standard system directories have | |
467 | been exhausted. @var{dir} is treated as a system include directory. | |
468 | If dir begins with @code{=}, then the @code{=} will be replaced by | |
469 | the sysroot prefix; see @option{--sysroot} and @option{-isysroot}. | |
470 | ||
670637ee DF |
471 | @item -imultilib @var{dir} |
472 | @opindex @code{imultilib @var{dir}} | |
473 | @cindex preprocessing, include path | |
474 | Use @var{dir} as a subdirectory of the directory containing target-specific | |
475 | C++ headers. | |
476 | ||
477 | @item -iprefix @var{prefix} | |
478 | @opindex @code{iprefix @var{prefix}} | |
479 | @cindex preprocessing, include path | |
480 | Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix} | |
481 | options. If the @var{prefix} represents a directory, you should include | |
482 | the final @code{'/'}. | |
483 | ||
484 | @item -isysroot @var{dir} | |
485 | @opindex @code{isysroot @var{dir}} | |
486 | @cindex preprocessing, include path | |
487 | This option is like the @option{--sysroot} option, but applies only to | |
488 | header files. See the @option{--sysroot} option for more information. | |
489 | ||
490 | @item -iquote @var{dir} | |
491 | @opindex @code{iquote @var{dir}} | |
492 | @cindex preprocessing, include path | |
493 | Search @var{dir} only for header files requested with @code{#include "file"}; | |
494 | they are not searched for @code{#include <file>}, before all directories | |
495 | specified by @option{-I} and before the standard system directories. If | |
496 | @var{dir} begins with @code{=}, then the @code{=} will be replaced by the | |
497 | sysroot prefix; see @option{--sysroot} and @option{-isysroot}. | |
498 | ||
499 | @item -isystem @var{dir} | |
500 | @opindex @code{isystem @var{dir}} | |
501 | @cindex preprocessing, include path | |
502 | Search @var{dir} for header files, after all directories specified by | |
503 | @option{-I} but before the standard system directories. Mark it as a | |
504 | system directory, so that it gets the same special treatment as is | |
505 | applied to the standard system directories. If @var{dir} begins with | |
506 | @code{=}, then the @code{=} will be replaced by the sysroot prefix; | |
507 | see @option{--sysroot} and @option{-isysroot}. | |
508 | ||
509 | @item -nostdinc | |
510 | @opindex @code{nostdinc} | |
511 | Do not search the standard system directories for header files. Only | |
512 | the directories you have specified with @option{-I} options (and the | |
513 | directory of the current file, if appropriate) are searched. | |
514 | ||
515 | @item -undef | |
516 | @opindex @code{undef} | |
517 | Do not predefine any system-specific or GCC-specific macros. | |
518 | The standard predefined macros remain defined. | |
519 | ||
520 | @item -A@var{predicate}=@var{answer} | |
521 | @opindex @code{A@var{predicate}=@var{answer}} | |
522 | @cindex preprocessing, assertation | |
523 | Make an assertion with the predicate @var{predicate} and answer @var{answer}. | |
524 | This form is preferred to the older form -A predicate(answer), which is still | |
525 | supported, because it does not use shell special characters. | |
526 | ||
527 | @item -A-@var{predicate}=@var{answer} | |
528 | @opindex @code{A-@var{predicate}=@var{answer}} | |
529 | @cindex preprocessing, assertation | |
530 | Cancel an assertion with the predicate @var{predicate} and answer @var{answer}. | |
531 | ||
532 | @item -C | |
533 | @opindex @code{C} | |
534 | @cindex preprocessing, keep comments | |
535 | Do not discard comments. All comments are passed through to the output | |
536 | file, except for comments in processed directives, which are deleted | |
537 | along with the directive. | |
538 | ||
539 | You should be prepared for side effects when using @option{-C}; it causes | |
540 | the preprocessor to treat comments as tokens in their own right. For example, | |
541 | comments appearing at the start of what would be a directive line have the | |
542 | effect of turning that line into an ordinary source line, since the first | |
543 | token on the line is no longer a @code{'#'}. | |
544 | ||
545 | Warning: this currently handles C-Style comments only. The preprocessor | |
546 | does not yet recognize Fortran-style comments. | |
547 | ||
548 | @item -CC | |
549 | @opindex @code{CC} | |
550 | @cindex preprocessing, keep comments | |
551 | Do not discard comments, including during macro expansion. This is like | |
552 | @option{-C}, except that comments contained within macros are also passed | |
553 | through to the output file where the macro is expanded. | |
554 | ||
555 | In addition to the side-effects of the @option{-C} option, the @option{-CC} | |
556 | option causes all C++-style comments inside a macro to be converted to C-style | |
557 | comments. This is to prevent later use of that macro from inadvertently | |
558 | commenting out the remainder of the source line. The @option{-CC} option | |
559 | is generally used to support lint comments. | |
560 | ||
561 | Warning: this currently handles C- and C++-Style comments only. The | |
562 | preprocessor does not yet recognize Fortran-style comments. | |
563 | ||
564 | @item -D@var{name} | |
565 | @opindex @code{D@var{name}} | |
566 | @cindex preprocessing, define macros | |
567 | Predefine name as a macro, with definition @code{1}. | |
568 | ||
569 | @item -D@var{name}=@var{definition} | |
570 | @opindex @code{D@var{name}=@var{definition}} | |
571 | @cindex preprocessing, define macros | |
572 | The contents of @var{definition} are tokenized and processed as if they | |
573 | appeared during translation phase three in a @code{'#define'} directive. | |
574 | In particular, the definition will be truncated by embedded newline | |
575 | characters. | |
576 | ||
577 | If you are invoking the preprocessor from a shell or shell-like program | |
578 | you may need to use the shell's quoting syntax to protect characters such | |
579 | as spaces that have a meaning in the shell syntax. | |
580 | ||
581 | If you wish to define a function-like macro on the command line, write | |
582 | its argument list with surrounding parentheses before the equals sign | |
583 | (if any). Parentheses are meaningful to most shells, so you will need | |
584 | to quote the option. With sh and csh, @code{-D'name(args...)=definition'} | |
585 | works. | |
586 | ||
587 | @option{-D} and @option{-U} options are processed in the order they are | |
588 | given on the command line. All -imacros file and -include file options | |
589 | are processed after all -D and -U options. | |
590 | ||
591 | @item -H | |
592 | @opindex @code{H} | |
593 | Print the name of each header file used, in addition to other normal | |
594 | activities. Each name is indented to show how deep in the @code{'#include'} | |
595 | stack it is. | |
596 | ||
597 | @item -P | |
598 | @opindex @code{P} | |
599 | @cindex preprocessing, no linemarkers | |
600 | Inhibit generation of linemarkers in the output from the preprocessor. | |
601 | This might be useful when running the preprocessor on something that | |
602 | is not C code, and will be sent to a program which might be confused | |
603 | by the linemarkers. | |
604 | ||
605 | @item -U@var{name} | |
606 | @opindex @code{U@var{name}} | |
607 | @cindex preprocessing, undefine macros | |
608 | Cancel any previous definition of @var{name}, either built in or provided | |
609 | with a @option{-D} option. | |
610 | @end table | |
611 | ||
612 | ||
592600ce | 613 | @node Error and Warning Options |
a2bef74c | 614 | @section Options to request or suppress errors and warnings |
6de9cd9a | 615 | @cindex options, warnings |
592600ce | 616 | @cindex options, errors |
6de9cd9a | 617 | @cindex warnings, suppressing |
592600ce | 618 | @cindex messages, error |
6de9cd9a DN |
619 | @cindex messages, warning |
620 | @cindex suppressing warnings | |
621 | ||
592600ce BM |
622 | Errors are diagnostic messages that report that the GNU Fortran compiler |
623 | cannot compile the relevant piece of source code. The compiler will | |
624 | continue to process the program in an attempt to report further errors | |
625 | to aid in debugging, but will not produce any compiled output. | |
626 | ||
6de9cd9a | 627 | Warnings are diagnostic messages that report constructions which |
592600ce | 628 | are not inherently erroneous but which are risky or suggest there is |
4ba96c02 | 629 | likely to be a bug in the program. Unless @option{-Werror} is specified, |
592600ce | 630 | they do not prevent compilation of the program. |
6de9cd9a DN |
631 | |
632 | You can request many specific warnings with options beginning @option{-W}, | |
633 | for example @option{-Wimplicit} to request warnings on implicit | |
634 | declarations. Each of these specific warning options also has a | |
635 | negative form beginning @option{-Wno-} to turn off warnings; | |
636 | for example, @option{-Wno-implicit}. This manual lists only one of the | |
637 | two forms, whichever is not the default. | |
638 | ||
592600ce BM |
639 | These options control the amount and kinds of errors and warnings produced |
640 | by GNU Fortran: | |
6de9cd9a DN |
641 | |
642 | @table @gcctabopt | |
efb66586 JD |
643 | @item -fmax-errors=@var{n} |
644 | @opindex @code{fmax-errors=}@var{n} | |
4ba96c02 | 645 | @cindex errors, limiting |
592600ce BM |
646 | Limits the maximum number of error messages to @var{n}, at which point |
647 | GNU Fortran bails out rather than attempting to continue processing the | |
648 | source code. If @var{n} is 0, there is no limit on the number of error | |
649 | messages produced. | |
650 | ||
6de9cd9a | 651 | @item -fsyntax-only |
32864778 | 652 | @opindex @code{fsyntax-only} |
4ba96c02 | 653 | @cindex syntax checking |
adeb22c4 FXC |
654 | Check the code for syntax errors, but don't actually compile it. This |
655 | will generate module files for each module present in the code, but no | |
656 | other output file. | |
6de9cd9a | 657 | |
6de9cd9a | 658 | @item -pedantic |
32864778 | 659 | @opindex @code{pedantic} |
7fc15ba5 | 660 | Issue warnings for uses of extensions to Fortran 95. |
6de9cd9a DN |
661 | @option{-pedantic} also applies to C-language constructs where they |
662 | occur in GNU Fortran source files, such as use of @samp{\e} in a | |
40746dcc | 663 | character constant within a directive like @code{#include}. |
6de9cd9a | 664 | |
7fc15ba5 | 665 | Valid Fortran 95 programs should compile properly with or without |
6de9cd9a DN |
666 | this option. |
667 | However, without this option, certain GNU extensions and traditional | |
668 | Fortran features are supported as well. | |
669 | With this option, many of them are rejected. | |
670 | ||
671 | Some users try to use @option{-pedantic} to check programs for conformance. | |
672 | They soon find that it does not do quite what they want---it finds some | |
673 | nonstandard practices, but not all. | |
7fc15ba5 | 674 | However, improvements to GNU Fortran in this area are welcome. |
6de9cd9a | 675 | |
f489fba1 FXC |
676 | This should be used in conjunction with @option{-std=f95}, |
677 | @option{-std=f2003} or @option{-std=f2008}. | |
6de9cd9a | 678 | |
6de9cd9a | 679 | @item -pedantic-errors |
32864778 | 680 | @opindex @code{pedantic-errors} |
6de9cd9a DN |
681 | Like @option{-pedantic}, except that errors are produced rather than |
682 | warnings. | |
683 | ||
6de9cd9a | 684 | @item -Wall |
32864778 | 685 | @opindex @code{Wall} |
6de9cd9a DN |
686 | @cindex all warnings |
687 | @cindex warnings, all | |
3fbab549 JD |
688 | Enables commonly used warning options pertaining to usage that |
689 | we recommend avoiding and that we believe are easy to avoid. | |
2e5758e8 | 690 | This currently includes @option{-Waliasing}, |
c3005b0f DK |
691 | @option{-Wampersand}, @option{-Wsurprising}, @option{-Wintrinsics-std}, |
692 | @option{-Wno-tabs}, @option{-Wintrinsic-shadow} and @option{-Wline-truncation}. | |
6de9cd9a | 693 | |
6de9cd9a | 694 | @item -Waliasing |
32864778 | 695 | @opindex @code{Waliasing} |
6de9cd9a | 696 | @cindex aliasing |
32864778 | 697 | @cindex warnings, aliasing |
3010be13 AD |
698 | Warn about possible aliasing of dummy arguments. Specifically, it warns |
699 | if the same actual argument is associated with a dummy argument with | |
40746dcc | 700 | @code{INTENT(IN)} and a dummy argument with @code{INTENT(OUT)} in a call |
3010be13 AD |
701 | with an explicit interface. |
702 | ||
703 | The following example will trigger the warning. | |
6de9cd9a | 704 | @smallexample |
3010be13 AD |
705 | interface |
706 | subroutine bar(a,b) | |
707 | integer, intent(in) :: a | |
708 | integer, intent(out) :: b | |
709 | end subroutine | |
710 | end interface | |
711 | integer :: a | |
712 | ||
713 | call bar(a,a) | |
6de9cd9a DN |
714 | @end smallexample |
715 | ||
3fbab549 | 716 | @item -Wampersand |
32864778 DF |
717 | @opindex @code{Wampersand} |
718 | @cindex warnings, ampersand | |
e739dfac | 719 | @cindex & |
3fbab549 | 720 | Warn about missing ampersand in continued character constants. The warning is |
f489fba1 FXC |
721 | given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95}, |
722 | @option{-std=f2003} and @option{-std=f2008}. Note: With no ampersand | |
723 | given in a continued character constant, GNU Fortran assumes continuation | |
724 | at the first non-comment, non-whitespace character after the ampersand | |
725 | that initiated the continuation. | |
3fbab549 | 726 | |
bdfd2ff0 TK |
727 | @item -Warray-temporaries |
728 | @opindex @code{Warray-temporaries} | |
729 | @cindex warnings, array temporaries | |
730 | Warn about array temporaries generated by the compiler. The information | |
731 | generated by this warning is sometimes useful in optimization, in order to | |
732 | avoid such temporaries. | |
733 | ||
276419d0 | 734 | @item -Wcharacter-truncation |
32864778 DF |
735 | @opindex @code{Wcharacter-truncation} |
736 | @cindex warnings, character truncation | |
276419d0 BM |
737 | Warn when a character assignment will truncate the assigned string. |
738 | ||
802e3f8c RW |
739 | @item -Wline-truncation |
740 | @opindex @code{Wline-truncation} | |
741 | @cindex warnings, line truncation | |
742 | Warn when a source code line will be truncated. | |
743 | ||
6de9cd9a | 744 | @item -Wconversion |
32864778 DF |
745 | @opindex @code{Wconversion} |
746 | @cindex warnings, conversion | |
6de9cd9a DN |
747 | @cindex conversion |
748 | Warn about implicit conversions between different types. | |
749 | ||
6de9cd9a | 750 | @item -Wimplicit-interface |
32864778 DF |
751 | @opindex @code{Wimplicit-interface} |
752 | @cindex warnings, implicit interface | |
02712c16 | 753 | Warn if a procedure is called without an explicit interface. |
6de9cd9a DN |
754 | Note this only checks that an explicit interface is present. It does not |
755 | check that the declared interfaces are consistent across program units. | |
756 | ||
ca071303 FXC |
757 | @item -Wimplicit-procedure |
758 | @opindex @code{Wimplicit-procedure} | |
759 | @cindex warnings, implicit procedure | |
760 | Warn if a procedure is called that has neither an explicit interface | |
761 | nor has been declared as @code{EXTERNAL}. | |
762 | ||
c3005b0f DK |
763 | @item -Wintrinsics-std |
764 | @opindex @code{Wintrinsics-std} | |
1207ac67 | 765 | @cindex warnings, non-standard intrinsics |
c3005b0f DK |
766 | @cindex warnings, intrinsics of other standards |
767 | Warn if @command{gfortran} finds a procedure named like an intrinsic not | |
768 | available in the currently selected standard (with @option{-std}) and treats | |
769 | it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can | |
c7d9f803 | 770 | be used to never trigger this behavior and always link to the intrinsic |
c3005b0f | 771 | regardless of the selected standard. |
b7892582 | 772 | |
6de9cd9a | 773 | @item -Wsurprising |
32864778 DF |
774 | @opindex @code{Wsurprising} |
775 | @cindex warnings, suspicious code | |
2d8b59df SK |
776 | Produce a warning when ``suspicious'' code constructs are encountered. |
777 | While technically legal these usually indicate that an error has been made. | |
6de9cd9a DN |
778 | |
779 | This currently produces a warning under the following circumstances: | |
780 | ||
781 | @itemize @bullet | |
782 | @item | |
ffd1953e FXC |
783 | An INTEGER SELECT construct has a CASE that can never be matched as its |
784 | lower value is greater than its upper value. | |
6de9cd9a DN |
785 | |
786 | @item | |
787 | A LOGICAL SELECT construct has three CASE statements. | |
39a184ce JD |
788 | |
789 | @item | |
790 | A TRANSFER specifies a source that is shorter than the destination. | |
fee3292b DK |
791 | |
792 | @item | |
793 | The type of a function result is declared more than once with the same type. If | |
794 | @option{-pedantic} or standard-conforming mode is enabled, this is an error. | |
5e1d6b4c DK |
795 | |
796 | @item | |
797 | A @code{CHARACTER} variable is declared with negative length. | |
6de9cd9a DN |
798 | @end itemize |
799 | ||
840bd9f7 | 800 | @item -Wtabs |
32864778 DF |
801 | @opindex @code{Wtabs} |
802 | @cindex warnings, tabs | |
e739dfac | 803 | @cindex tabulators |
840bd9f7 | 804 | By default, tabs are accepted as whitespace, but tabs are not members |
fd1935d5 TB |
805 | of the Fortran Character Set. For continuation lines, a tab followed |
806 | by a digit between 1 and 9 is supported. @option{-Wno-tabs} will cause | |
807 | a warning to be issued if a tab is encountered. Note, @option{-Wno-tabs} | |
808 | is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003}, | |
f489fba1 | 809 | @option{-std=f2008} and @option{-Wall}. |
840bd9f7 | 810 | |
2d8b59df | 811 | @item -Wunderflow |
32864778 DF |
812 | @opindex @code{Wunderflow} |
813 | @cindex warnings, underflow | |
814 | @cindex underflow | |
2d8b59df SK |
815 | Produce a warning when numerical constant expressions are |
816 | encountered, which yield an UNDERFLOW during compilation. | |
817 | ||
c3005b0f DK |
818 | @item -Wintrinsic-shadow |
819 | @opindex @code{Wintrinsic-shadow} | |
820 | @cindex warnings, intrinsic | |
821 | @cindex intrinsic | |
822 | Warn if a user-defined procedure or module procedure has the same name as an | |
823 | intrinsic; in this case, an explicit interface or @code{EXTERNAL} or | |
824 | @code{INTRINSIC} declaration might be needed to get calls later resolved to | |
825 | the desired intrinsic/procedure. | |
826 | ||
d92693b4 DF |
827 | @item -Wunused-parameter |
828 | @opindex @code{Wunused-parameter} | |
829 | @cindex warnings, unused parameter | |
830 | @cindex unused parameter | |
831 | Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter}, | |
832 | @command{gfortran}'s implementation of this option does not warn | |
833 | about unused dummy arguments, but about unused @code{PARAMETER} values. | |
834 | @option{-Wunused-parameter} is not included in @option{-Wall} but is | |
835 | implied by @option{-Wall -Wextra}. | |
836 | ||
f613cea7 JW |
837 | @item -Walign-commons |
838 | @opindex @code{Walign-commons} | |
839 | @cindex warnings, alignment of COMMON blocks | |
840 | @cindex alignment of COMMON blocks | |
841 | By default, @command{gfortran} warns about any occasion of variables being | |
842 | padded for proper alignment inside a COMMON block. This warning can be turned | |
843 | off via @option{-Wno-align-commons}. See also @option{-falign-commons}. | |
844 | ||
6de9cd9a | 845 | @item -Werror |
32864778 DF |
846 | @opindex @code{Werror} |
847 | @cindex warnings, to errors | |
6de9cd9a | 848 | Turns all warnings into errors. |
6de9cd9a DN |
849 | @end table |
850 | ||
592600ce BM |
851 | @xref{Error and Warning Options,,Options to Request or Suppress Errors and |
852 | Warnings, gcc,Using the GNU Compiler Collection (GCC)}, for information on | |
853 | more options offered by the GBE shared by @command{gfortran}, @command{gcc} | |
854 | and other GNU compilers. | |
6de9cd9a DN |
855 | |
856 | Some of these have no effect when compiling programs written in Fortran. | |
857 | ||
858 | @node Debugging Options | |
a2bef74c | 859 | @section Options for debugging your program or GNU Fortran |
6de9cd9a DN |
860 | @cindex options, debugging |
861 | @cindex debugging information options | |
862 | ||
863 | GNU Fortran has various special options that are used for debugging | |
7fc15ba5 | 864 | either your program or the GNU Fortran compiler. |
6de9cd9a DN |
865 | |
866 | @table @gcctabopt | |
6de9cd9a | 867 | @item -fdump-parse-tree |
32864778 | 868 | @opindex @code{fdump-parse-tree} |
6de9cd9a | 869 | Output the internal parse tree before starting code generation. Only |
7fc15ba5 | 870 | really useful for debugging the GNU Fortran compiler itself. |
6de9cd9a | 871 | |
944b8b35 | 872 | @item -ffpe-trap=@var{list} |
32864778 | 873 | @opindex @code{ffpe-trap=}@var{list} |
944b8b35 FXC |
874 | Specify a list of IEEE exceptions when a Floating Point Exception |
875 | (FPE) should be raised. On most systems, this will result in a SIGFPE | |
876 | signal being sent and the program being interrupted, producing a core | |
877 | file useful for debugging. @var{list} is a (possibly empty) comma-separated | |
878 | list of the following IEEE exceptions: @samp{invalid} (invalid floating | |
40746dcc | 879 | point operation, such as @code{SQRT(-1.0)}), @samp{zero} (division by |
944b8b35 FXC |
880 | zero), @samp{overflow} (overflow in a floating point operation), |
881 | @samp{underflow} (underflow in a floating point operation), | |
882 | @samp{precision} (loss of precision during operation) and @samp{denormal} | |
27ea0360 | 883 | (operation produced a denormal value). |
eedeea04 | 884 | |
8307c61b | 885 | Some of the routines in the Fortran runtime library, like |
aad9c4f4 | 886 | @samp{CPU_TIME}, are likely to trigger floating point exceptions when |
8307c61b FXC |
887 | @code{ffpe-trap=precision} is used. For this reason, the use of |
888 | @code{ffpe-trap=precision} is not recommended. | |
889 | ||
868d75db | 890 | @item -fbacktrace |
32864778 | 891 | @opindex @code{fbacktrace} |
868d75db FXC |
892 | @cindex backtrace |
893 | @cindex trace | |
2b840e50 FXC |
894 | Specify that, when a runtime error is encountered or a deadly signal is |
895 | emitted (segmentation fault, illegal instruction, bus error or | |
896 | floating-point exception), the Fortran runtime | |
868d75db FXC |
897 | library should output a backtrace of the error. This option |
898 | only has influence for compilation of the Fortran main program. | |
899 | ||
eedeea04 | 900 | @item -fdump-core |
e739dfac DF |
901 | @cindex core, dump |
902 | @opindex @code{fdump-core} | |
eedeea04 FXC |
903 | Request that a core-dump file is written to disk when a runtime error |
904 | is encountered on systems that support core dumps. This option is | |
905 | only effective for the compilation of the Fortran main program. | |
944b8b35 FXC |
906 | @end table |
907 | ||
6de9cd9a DN |
908 | @xref{Debugging Options,,Options for Debugging Your Program or GCC, |
909 | gcc,Using the GNU Compiler Collection (GCC)}, for more information on | |
910 | debugging options. | |
911 | ||
912 | @node Directory Options | |
a2bef74c | 913 | @section Options for directory search |
6de9cd9a DN |
914 | @cindex directory, options |
915 | @cindex options, directory search | |
916 | @cindex search path | |
6de9cd9a DN |
917 | @cindex INCLUDE directive |
918 | @cindex directive, INCLUDE | |
7fc15ba5 | 919 | These options affect how GNU Fortran searches |
5724da63 | 920 | for files specified by the @code{INCLUDE} directive and where it searches |
6de9cd9a DN |
921 | for previously compiled modules. |
922 | ||
923 | It also affects the search paths used by @command{cpp} when used to preprocess | |
2d8b59df | 924 | Fortran source. |
6de9cd9a DN |
925 | |
926 | @table @gcctabopt | |
6de9cd9a | 927 | @item -I@var{dir} |
32864778 | 928 | @opindex @code{I}@var{dir} |
6de9cd9a DN |
929 | @cindex directory, search paths for inclusion |
930 | @cindex inclusion, directory search paths for | |
931 | @cindex search paths, for included files | |
932 | @cindex paths, search | |
933 | @cindex module search path | |
934 | These affect interpretation of the @code{INCLUDE} directive | |
935 | (as well as of the @code{#include} directive of the @command{cpp} | |
936 | preprocessor). | |
937 | ||
938 | Also note that the general behavior of @option{-I} and | |
939 | @code{INCLUDE} is pretty much the same as of @option{-I} with | |
940 | @code{#include} in the @command{cpp} preprocessor, with regard to | |
941 | looking for @file{header.gcc} files and other such things. | |
942 | ||
40746dcc | 943 | This path is also used to search for @file{.mod} files when previously |
6de9cd9a DN |
944 | compiled modules are required by a @code{USE} statement. |
945 | ||
946 | @xref{Directory Options,,Options for Directory Search, | |
947 | gcc,Using the GNU Compiler Collection (GCC)}, for information on the | |
948 | @option{-I} option. | |
949 | ||
6de9cd9a | 950 | @item -J@var{dir} |
ccc2ed87 | 951 | @item -M@var{dir} |
32864778 | 952 | @opindex @code{J}@var{dir} |
ccc2ed87 | 953 | @opindex @code{M}@var{dir} |
276419d0 BM |
954 | @cindex paths, search |
955 | @cindex module search path | |
40746dcc | 956 | This option specifies where to put @file{.mod} files for compiled modules. |
2d8b59df | 957 | It is also added to the list of directories to searched by an @code{USE} |
6de9cd9a DN |
958 | statement. |
959 | ||
960 | The default is the current directory. | |
961 | ||
ccc2ed87 | 962 | @option{-M} is deprecated to avoid conflicts with existing GCC options. |
276419d0 BM |
963 | |
964 | @item -fintrinsic-modules-path @var{dir} | |
32864778 | 965 | @opindex @code{fintrinsic-modules-path} @var{dir} |
276419d0 BM |
966 | @cindex paths, search |
967 | @cindex module search path | |
968 | This option specifies the location of pre-compiled intrinsic modules, if | |
969 | they are not in the default location expected by the compiler. | |
6de9cd9a DN |
970 | @end table |
971 | ||
70263321 | 972 | @node Link Options |
a2bef74c | 973 | @section Influencing the linking step |
70263321 DF |
974 | @cindex options, linking |
975 | @cindex linking, static | |
976 | ||
977 | These options come into play when the compiler links object files into an | |
978 | executable output file. They are meaningless if the compiler is not doing | |
979 | a link step. | |
980 | ||
981 | @table @gcctabopt | |
982 | @item -static-libgfortran | |
983 | @opindex @code{static-libgfortran} | |
984 | On systems that provide @file{libgfortran} as a shared and a static | |
985 | library, this option forces the use of the static version. If no | |
986 | shared version of @file{libgfortran} was built when the compiler was | |
987 | configured, this option has no effect. | |
988 | @end table | |
989 | ||
990 | ||
eaa90d25 | 991 | @node Runtime Options |
a2bef74c | 992 | @section Influencing runtime behavior |
e739dfac | 993 | @cindex options, runtime |
eaa90d25 | 994 | |
7fc15ba5 | 995 | These options affect the runtime behavior of programs compiled with GNU Fortran. |
eaa90d25 | 996 | @table @gcctabopt |
eaa90d25 | 997 | @item -fconvert=@var{conversion} |
32864778 | 998 | @opindex @code{fconvert=}@var{conversion} |
eaa90d25 TK |
999 | Specify the representation of data for unformatted files. Valid |
1000 | values for conversion are: @samp{native}, the default; @samp{swap}, | |
1001 | swap between big- and little-endian; @samp{big-endian}, use big-endian | |
1002 | representation for unformatted files; @samp{little-endian}, use little-endian | |
1003 | representation for unformatted files. | |
1004 | ||
1005 | @emph{This option has an effect only when used in the main program. | |
1006 | The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment | |
40746dcc | 1007 | variable override the default specified by @option{-fconvert}.} |
d67ab5ee | 1008 | |
082b0571 JD |
1009 | |
1010 | @item -fno-range-check | |
c3280643 | 1011 | @opindex @code{fno-range-check} |
082b0571 JD |
1012 | Disable range checking of input values during integer @code{READ} operations. |
1013 | For example, GNU Fortran will give an error if an input value is | |
1014 | outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}]. In other words, | |
1015 | with @code{INTEGER (kind=4) :: i} , attempting to read @math{-2147483648} will | |
1016 | give an error unless @option{-fno-range-check} is given. | |
1017 | ||
1018 | ||
d67ab5ee | 1019 | @item -frecord-marker=@var{length} |
32864778 | 1020 | @opindex @code{frecord-marker=}@var{length} |
d67ab5ee | 1021 | Specify the length of record markers for unformatted files. |
07b3bbf2 | 1022 | Valid values for @var{length} are 4 and 8. Default is 4. |
a2bef74c | 1023 | @emph{This is different from previous versions of @command{gfortran}}, |
07b3bbf2 TK |
1024 | which specified a default record marker length of 8 on most |
1025 | systems. If you want to read or write files compatible | |
a2bef74c | 1026 | with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}. |
07b3bbf2 | 1027 | |
07b3bbf2 | 1028 | @item -fmax-subrecord-length=@var{length} |
32864778 | 1029 | @opindex @code{fmax-subrecord-length=}@var{length} |
07b3bbf2 TK |
1030 | Specify the maximum length for a subrecord. The maximum permitted |
1031 | value for length is 2147483639, which is also the default. Only | |
1032 | really useful for use by the gfortran testsuite. | |
0483c79f JD |
1033 | |
1034 | @item -fsign-zero | |
1035 | @opindex @code{fsign-zero} | |
60d340ef TB |
1036 | When enabled, floating point numbers of value zero with the sign bit set |
1037 | are written as negative number in formatted output and treated as | |
1038 | negative in the @code{SIGN} intrinsic. @code{fno-sign-zero} does not | |
1039 | print the negative sign of zero values and regards zero as positive | |
1040 | number in the @code{SIGN} intrinsic for compatibility with F77. | |
1041 | Default behavior is to show the negative sign. | |
eaa90d25 TK |
1042 | @end table |
1043 | ||
6de9cd9a | 1044 | @node Code Gen Options |
a2bef74c | 1045 | @section Options for code generation conventions |
6de9cd9a DN |
1046 | @cindex code generation, conventions |
1047 | @cindex options, code generation | |
e739dfac | 1048 | @cindex options, run-time |
6de9cd9a DN |
1049 | |
1050 | These machine-independent options control the interface conventions | |
1051 | used in code generation. | |
1052 | ||
1053 | Most of them have both positive and negative forms; the negative form | |
1054 | of @option{-ffoo} would be @option{-fno-foo}. In the table below, only | |
1055 | one of the forms is listed---the one which is not the default. You | |
1056 | can figure out the other form by either removing @option{no-} or adding | |
1057 | it. | |
1058 | ||
6de9cd9a | 1059 | @table @gcctabopt |
ee5426a4 | 1060 | @item -fno-automatic |
32864778 | 1061 | @opindex @code{fno-automatic} |
e739dfac DF |
1062 | @cindex @code{SAVE} statement |
1063 | @cindex statement, @code{SAVE} | |
1e7de83b AL |
1064 | Treat each program unit (except those marked as RECURSIVE) as if the |
1065 | @code{SAVE} statement were specified for every local variable and array | |
1066 | referenced in it. Does not affect common blocks. (Some Fortran compilers | |
1067 | provide this option under the name @option{-static} or @option{-save}.) | |
1068 | The default, which is @option{-fautomatic}, uses the stack for local | |
1069 | variables smaller than the value given by @option{-fmax-stack-var-size}. | |
1070 | Use the option @option{-frecursive} to use no static memory. | |
ee5426a4 | 1071 | |
973ff4c0 | 1072 | @item -ff2c |
e739dfac | 1073 | @opindex ff2c |
973ff4c0 TS |
1074 | @cindex calling convention |
1075 | @cindex @command{f2c} calling convention | |
1076 | @cindex @command{g77} calling convention | |
1077 | @cindex libf2c calling convention | |
1078 | Generate code designed to be compatible with code generated | |
1079 | by @command{g77} and @command{f2c}. | |
1080 | ||
1081 | The calling conventions used by @command{g77} (originally implemented | |
1082 | in @command{f2c}) require functions that return type | |
1083 | default @code{REAL} to actually return the C type @code{double}, and | |
1084 | functions that return type @code{COMPLEX} to return the values via an | |
1085 | extra argument in the calling sequence that points to where to | |
1086 | store the return value. Under the default GNU calling conventions, such | |
1087 | functions simply return their results as they would in GNU | |
8556236b | 1088 | C---default @code{REAL} functions return the C type @code{float}, and |
973ff4c0 | 1089 | @code{COMPLEX} functions return the GNU C type @code{complex}. |
a226fc2b TS |
1090 | Additionally, this option implies the @option{-fsecond-underscore} |
1091 | option, unless @option{-fno-second-underscore} is explicitly requested. | |
973ff4c0 TS |
1092 | |
1093 | This does not affect the generation of code that interfaces with | |
1094 | the @command{libgfortran} library. | |
1095 | ||
40746dcc BM |
1096 | @emph{Caution:} It is not a good idea to mix Fortran code compiled with |
1097 | @option{-ff2c} with code compiled with the default @option{-fno-f2c} | |
973ff4c0 TS |
1098 | calling conventions as, calling @code{COMPLEX} or default @code{REAL} |
1099 | functions between program parts which were compiled with different | |
1100 | calling conventions will break at execution time. | |
1101 | ||
1102 | @emph{Caution:} This will break code which passes intrinsic functions | |
1103 | of type default @code{REAL} or @code{COMPLEX} as actual arguments, as | |
40746dcc | 1104 | the library implementations use the @option{-fno-f2c} calling conventions. |
973ff4c0 | 1105 | |
6de9cd9a | 1106 | @item -fno-underscoring |
32864778 | 1107 | @opindex @code{fno-underscoring} |
6de9cd9a DN |
1108 | @cindex underscore |
1109 | @cindex symbol names, underscores | |
1110 | @cindex transforming symbol names | |
1111 | @cindex symbol names, transforming | |
1112 | Do not transform names of entities specified in the Fortran | |
1113 | source file by appending underscores to them. | |
1114 | ||
7fc15ba5 | 1115 | With @option{-funderscoring} in effect, GNU Fortran appends one |
5724da63 JD |
1116 | underscore to external names with no underscores. This is done to ensure |
1117 | compatibility with code produced by many UNIX Fortran compilers. | |
973ff4c0 | 1118 | |
7fc15ba5 | 1119 | @emph{Caution}: The default behavior of GNU Fortran is |
973ff4c0 | 1120 | incompatible with @command{f2c} and @command{g77}, please use the |
b4cbcd1a | 1121 | @option{-ff2c} option if you want object files compiled with |
7fc15ba5 | 1122 | GNU Fortran to be compatible with object code created with these |
b4cbcd1a | 1123 | tools. |
6de9cd9a DN |
1124 | |
1125 | Use of @option{-fno-underscoring} is not recommended unless you are | |
7fc15ba5 | 1126 | experimenting with issues such as integration of GNU Fortran into |
8307c61b FXC |
1127 | existing system environments (vis-@`{a}-vis existing libraries, tools, |
1128 | and so on). | |
6de9cd9a DN |
1129 | |
1130 | For example, with @option{-funderscoring}, and assuming other defaults like | |
40746dcc BM |
1131 | @option{-fcase-lower} and that @code{j()} and @code{max_count()} are |
1132 | external functions while @code{my_var} and @code{lvar} are local variables, | |
6de9cd9a | 1133 | a statement like |
6de9cd9a DN |
1134 | @smallexample |
1135 | I = J() + MAX_COUNT (MY_VAR, LVAR) | |
1136 | @end smallexample | |
6de9cd9a DN |
1137 | @noindent |
1138 | is implemented as something akin to: | |
6de9cd9a DN |
1139 | @smallexample |
1140 | i = j_() + max_count__(&my_var__, &lvar); | |
1141 | @end smallexample | |
1142 | ||
1143 | With @option{-fno-underscoring}, the same statement is implemented as: | |
1144 | ||
1145 | @smallexample | |
1146 | i = j() + max_count(&my_var, &lvar); | |
1147 | @end smallexample | |
1148 | ||
1149 | Use of @option{-fno-underscoring} allows direct specification of | |
7fc15ba5 | 1150 | user-defined names while debugging and when interfacing GNU Fortran |
6de9cd9a DN |
1151 | code with other languages. |
1152 | ||
1153 | Note that just because the names match does @emph{not} mean that the | |
7fc15ba5 | 1154 | interface implemented by GNU Fortran for an external name matches the |
6de9cd9a | 1155 | interface implemented by some other language for that same name. |
7fc15ba5 | 1156 | That is, getting code produced by GNU Fortran to link to code produced |
6de9cd9a DN |
1157 | by some other compiler using this or any other method can be only a |
1158 | small part of the overall solution---getting the code generated by | |
1159 | both compilers to agree on issues other than naming can require | |
1160 | significant effort, and, unlike naming disagreements, linkers normally | |
1161 | cannot detect disagreements in these other areas. | |
1162 | ||
1163 | Also, note that with @option{-fno-underscoring}, the lack of appended | |
1164 | underscores introduces the very real possibility that a user-defined | |
1165 | external name will conflict with a name in a system library, which | |
1166 | could make finding unresolved-reference bugs quite difficult in some | |
1167 | cases---they might occur at program run time, and show up only as | |
1168 | buggy behavior at run time. | |
1169 | ||
7fc15ba5 | 1170 | In future versions of GNU Fortran we hope to improve naming and linking |
6de9cd9a DN |
1171 | issues so that debugging always involves using the names as they appear |
1172 | in the source, even if the names as seen by the linker are mangled to | |
1173 | prevent accidental linking between procedures with incompatible | |
1174 | interfaces. | |
1175 | ||
71a7778c PT |
1176 | @item -fwhole-file |
1177 | @opindex @code{fwhole-file} | |
1178 | By default, GNU Fortran parses, resolves and translates each procedure | |
1179 | in a file separately. Using this option modifies this such that the | |
1180 | whole file is parsed and placed in a single front-end tree. During | |
1181 | resolution, in addition to all the usual checks and fixups, references | |
1182 | to external procedures that are in the same file effect resolution of | |
1183 | that procedure, if not already done, and a check of the interfaces. The | |
1184 | dependences are resolved by changing the order in which the file is | |
1185 | translated into the backend tree. Thus, a procedure that is referenced | |
1186 | is translated before the reference and the duplication of backend tree | |
1187 | declarations eliminated. | |
1188 | ||
973ff4c0 | 1189 | @item -fsecond-underscore |
32864778 | 1190 | @opindex @code{fsecond-underscore} |
6de9cd9a DN |
1191 | @cindex underscore |
1192 | @cindex symbol names, underscores | |
1193 | @cindex transforming symbol names | |
1194 | @cindex symbol names, transforming | |
973ff4c0 TS |
1195 | @cindex @command{f2c} calling convention |
1196 | @cindex @command{g77} calling convention | |
1197 | @cindex libf2c calling convention | |
7fc15ba5 BM |
1198 | By default, GNU Fortran appends an underscore to external |
1199 | names. If this option is used GNU Fortran appends two | |
973ff4c0 | 1200 | underscores to names with underscores and one underscore to external names |
7fc15ba5 | 1201 | with no underscores. GNU Fortran also appends two underscores to |
973ff4c0 TS |
1202 | internal names with underscores to avoid naming collisions with external |
1203 | names. | |
6de9cd9a DN |
1204 | |
1205 | This option has no effect if @option{-fno-underscoring} is | |
973ff4c0 | 1206 | in effect. It is implied by the @option{-ff2c} option. |
6de9cd9a | 1207 | |
40746dcc | 1208 | Otherwise, with this option, an external name such as @code{MAX_COUNT} |
6de9cd9a | 1209 | is implemented as a reference to the link-time external symbol |
40746dcc | 1210 | @code{max_count__}, instead of @code{max_count_}. This is required |
973ff4c0 TS |
1211 | for compatibility with @command{g77} and @command{f2c}, and is implied |
1212 | by use of the @option{-ff2c} option. | |
6de9cd9a | 1213 | |
d3d3011f FXC |
1214 | @item -fcheck=@var{<keyword>} |
1215 | @opindex @code{fcheck} | |
e739dfac | 1216 | @cindex array, bounds checking |
6de9cd9a | 1217 | @cindex bounds checking |
20460eb9 | 1218 | @cindex pointer checking |
22bdbb0f | 1219 | @cindex memory checking |
6de9cd9a | 1220 | @cindex range checking |
6de9cd9a DN |
1221 | @cindex subscript checking |
1222 | @cindex checking subscripts | |
d3d3011f FXC |
1223 | @cindex run-time checking |
1224 | @cindex checking array temporaries | |
1225 | ||
1226 | Enable the generation of run-time checks; the argument shall be | |
1227 | a comma-delimited list of the following keywords. | |
1228 | ||
1229 | @table @asis | |
1230 | @item @samp{all} | |
1231 | Enable all run-time test of @option{-fcheck}. | |
1232 | ||
1233 | @item @samp{array-temps} | |
1234 | Warns at run time when for passing an actual argument a temporary array | |
1235 | had to be generated. The information generated by this warning is | |
1236 | sometimes useful in optimization, in order to avoid such temporaries. | |
1237 | ||
1238 | Note: The warning is only printed once per location. | |
1239 | ||
1240 | @item @samp{bounds} | |
6de9cd9a DN |
1241 | Enable generation of run-time checks for array subscripts |
1242 | and against the declared minimum and maximum values. It also | |
1243 | checks array indices for assumed and deferred | |
aad9c4f4 AM |
1244 | shape arrays against the actual allocated bounds and ensures that all string |
1245 | lengths are equal for character array constructors without an explicit | |
1246 | typespec. | |
6de9cd9a | 1247 | |
d3d3011f | 1248 | Some checks require that @option{-fcheck=bounds} is set for |
8307c61b | 1249 | the compilation of the main program. |
18fe404f | 1250 | |
aad9c4f4 AM |
1251 | Note: In the future this may also include other forms of checking, e.g., |
1252 | checking substring references. | |
43998ed9 | 1253 | |
33abc845 TB |
1254 | @item @samp{do} |
1255 | Enable generation of run-time checks for invalid modification of loop | |
1256 | iteration variables. | |
1257 | ||
22bdbb0f TB |
1258 | @item @samp{mem} |
1259 | Enable generation of run-time checks for memory allocation. | |
1260 | Note: This option does not affect explicit allocations using the | |
1261 | @code{ALLOCATE} statement, which will be always checked. | |
1262 | ||
20460eb9 TB |
1263 | @item @samp{pointer} |
1264 | Enable generation of run-time checks for pointers and allocatables. | |
1265 | ||
43998ed9 TB |
1266 | @item @samp{recursion} |
1267 | Enable generation of run-time checks for recursively called subroutines and | |
1268 | functions which are not marked as recursive. See also @option{-frecursive}. | |
8b5f6dd8 | 1269 | Note: This check does not work for OpenMP programs and is disabled if used |
5b130807 | 1270 | together with @option{-frecursive} and @option{-fopenmp}. |
d3d3011f | 1271 | @end table |
6de9cd9a | 1272 | |
0d52899f | 1273 | |
d3d3011f FXC |
1274 | @item -fbounds-check |
1275 | @opindex @code{fbounds-check} | |
1276 | @c Note: This option is also referred in gcc's manpage | |
1277 | Deprecated alias for @option{-fcheck=bounds}. | |
0d52899f | 1278 | |
d3d3011f FXC |
1279 | @item -fcheck-array-temporaries |
1280 | @opindex @code{fcheck-array-temporaries} | |
1281 | Deprecated alias for @option{-fcheck=array-temps}. | |
0d52899f | 1282 | |
63346ddb SK |
1283 | @item -fmax-array-constructor=@var{n} |
1284 | @opindex @code{fmax-array-constructor} | |
1285 | This option can be used to increase the upper limit permitted in | |
1286 | array constructors. The code below requires this option to expand | |
1287 | the array at compile time. | |
1288 | ||
1289 | @smallexample | |
1290 | @code{program test} | |
1291 | @code{implicit none} | |
1292 | @code{integer j} | |
1293 | @code{integer, parameter :: n = 100000} | |
1294 | @code{integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)} | |
1295 | @code{print '(10(I0,1X))', i} | |
1296 | @code{end program test} | |
1297 | @end smallexample | |
1298 | ||
1299 | @emph{Caution: This option can lead to long compile times and excessively | |
1300 | large object files.} | |
1301 | ||
1302 | The default value for @var{n} is 65535. | |
1303 | ||
1304 | ||
6de9cd9a | 1305 | @item -fmax-stack-var-size=@var{n} |
32864778 | 1306 | @opindex @code{fmax-stack-var-size} |
6de9cd9a | 1307 | This option specifies the size in bytes of the largest array that will be put |
1e7de83b AL |
1308 | on the stack; if the size is exceeded static memory is used (except in |
1309 | procedures marked as RECURSIVE). Use the option @option{-frecursive} to | |
1310 | allow for recursive procedures which do not have a RECURSIVE attribute or | |
1311 | for parallel programs. Use @option{-fno-automatic} to never use the stack. | |
6de9cd9a DN |
1312 | |
1313 | This option currently only affects local arrays declared with constant | |
1314 | bounds, and may not apply to all character variables. | |
7fc15ba5 | 1315 | Future versions of GNU Fortran may improve this behavior. |
6de9cd9a DN |
1316 | |
1317 | The default value for @var{n} is 32768. | |
1318 | ||
5139e1e9 | 1319 | @item -fpack-derived |
32864778 DF |
1320 | @opindex @code{fpack-derived} |
1321 | @cindex structure packing | |
7fc15ba5 | 1322 | This option tells GNU Fortran to pack derived type members as closely as |
2d8b59df | 1323 | possible. Code compiled with this option is likely to be incompatible |
6de9cd9a DN |
1324 | with code compiled without this option, and may execute slower. |
1325 | ||
6de9cd9a | 1326 | @item -frepack-arrays |
32864778 DF |
1327 | @opindex @code{frepack-arrays} |
1328 | @cindex repacking arrays | |
7fc15ba5 | 1329 | In some circumstances GNU Fortran may pass assumed shape array |
02712c16 | 1330 | sections via a descriptor describing a noncontiguous area of memory. |
6de9cd9a DN |
1331 | This option adds code to the function prologue to repack the data into |
1332 | a contiguous block at runtime. | |
1333 | ||
1334 | This should result in faster accesses to the array. However it can introduce | |
1335 | significant overhead to the function call, especially when the passed data | |
02712c16 | 1336 | is noncontiguous. |
a63dad5b | 1337 | |
a63dad5b | 1338 | @item -fshort-enums |
32864778 | 1339 | @opindex @code{fshort-enums} |
a63dad5b | 1340 | This option is provided for interoperability with C code that was |
4ba96c02 | 1341 | compiled with the @option{-fshort-enums} option. It will make |
7fc15ba5 | 1342 | GNU Fortran choose the smallest @code{INTEGER} kind a given |
a63dad5b | 1343 | enumerator set will fit in, and give all its enumerators this kind. |
5a0aad31 | 1344 | |
5a0aad31 | 1345 | @item -fexternal-blas |
32864778 | 1346 | @opindex @code{fexternal-blas} |
a2bef74c DF |
1347 | This option will make @command{gfortran} generate calls to BLAS functions |
1348 | for some matrix operations like @code{MATMUL}, instead of using our own | |
5a0aad31 | 1349 | algorithms, if the size of the matrices involved is larger than a given |
4ba96c02 | 1350 | limit (see @option{-fblas-matmul-limit}). This may be profitable if an |
5a0aad31 FXC |
1351 | optimized vendor BLAS library is available. The BLAS library will have |
1352 | to be specified at link time. | |
1353 | ||
5a0aad31 | 1354 | @item -fblas-matmul-limit=@var{n} |
32864778 | 1355 | @opindex @code{fblas-matmul-limit} |
4ba96c02 | 1356 | Only significant when @option{-fexternal-blas} is in effect. |
5a0aad31 FXC |
1357 | Matrix multiplication of matrices with size larger than (or equal to) @var{n} |
1358 | will be performed by calls to BLAS functions, while others will be | |
1359 | handled by @command{gfortran} internal algorithms. If the matrices | |
1360 | involved are not square, the size comparison is performed using the | |
1361 | geometric mean of the dimensions of the argument and result matrices. | |
1362 | ||
1363 | The default value for @var{n} is 30. | |
1364 | ||
1e7de83b AL |
1365 | @item -frecursive |
1366 | @opindex @code{frecursive} | |
1367 | Allow indirect recursion by forcing all local arrays to be allocated | |
1368 | on the stack. This flag cannot be used together with | |
1369 | @option{-fmax-stack-var-size=} or @option{-fno-automatic}. | |
1370 | ||
51b09ce3 AL |
1371 | @item -finit-local-zero |
1372 | @item -finit-integer=@var{n} | |
346a77d1 | 1373 | @item -finit-real=@var{<zero|inf|-inf|nan|snan>} |
51b09ce3 AL |
1374 | @item -finit-logical=@var{<true|false>} |
1375 | @item -finit-character=@var{n} | |
1376 | @opindex @code{finit-local-zero} | |
1377 | @opindex @code{finit-integer} | |
1378 | @opindex @code{finit-real} | |
1379 | @opindex @code{finit-logical} | |
1380 | @opindex @code{finit-character} | |
1381 | The @option{-finit-local-zero} option instructs the compiler to | |
1382 | initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX} | |
1383 | variables to zero, @code{LOGICAL} variables to false, and | |
1384 | @code{CHARACTER} variables to a string of null bytes. Finer-grained | |
1385 | initialization options are provided by the | |
1386 | @option{-finit-integer=@var{n}}, | |
346a77d1 | 1387 | @option{-finit-real=@var{<zero|inf|-inf|nan|snan>}} (which also initializes |
51b09ce3 AL |
1388 | the real and imaginary parts of local @code{COMPLEX} variables), |
1389 | @option{-finit-logical=@var{<true|false>}}, and | |
1390 | @option{-finit-character=@var{n}} (where @var{n} is an ASCII character | |
1391 | value) options. These options do not initialize components of derived | |
1392 | type variables, nor do they initialize variables that appear in an | |
1393 | @code{EQUIVALENCE} statement. (This limitation may be removed in | |
1394 | future releases). | |
1395 | ||
1396 | Note that the @option{-finit-real=nan} option initializes @code{REAL} | |
346a77d1 TB |
1397 | and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN |
1398 | use @option{-finit-real=snan}; note, however, that compile-time | |
1399 | optimizations may convert them into quiet NaN and that trapping | |
1400 | needs to be enabled (e.g. via @option{-ffpe-trap}). | |
f613cea7 JW |
1401 | |
1402 | @item -falign-commons | |
1403 | @opindex @code{falign-commons} | |
1404 | @cindex alignment of COMMON blocks | |
1405 | By default, @command{gfortran} enforces proper alignment of all variables in a | |
1406 | COMMON block by padding them as needed. On certain platforms this is mandatory, | |
1407 | on others it increases performance. If a COMMON block is not declared with | |
1408 | consistent data types everywhere, this padding can cause trouble, and | |
1409 | @option{-fno-align-commons } can be used to disable automatic alignment. The | |
1410 | same form of this option should be used for all files that share a COMMON block. | |
1411 | To avoid potential alignment issues in COMMON blocks, it is recommended to order | |
1412 | objects from largests to smallest. | |
6de9cd9a DN |
1413 | @end table |
1414 | ||
1415 | @xref{Code Gen Options,,Options for Code Generation Conventions, | |
1416 | gcc,Using the GNU Compiler Collection (GCC)}, for information on more options | |
1417 | offered by the GBE | |
7fc15ba5 | 1418 | shared by @command{gfortran}, @command{gcc}, and other GNU compilers. |
6de9cd9a DN |
1419 | |
1420 | ||
1421 | @c man end | |
1422 | ||
1423 | @node Environment Variables | |
a2bef74c | 1424 | @section Environment variables affecting @command{gfortran} |
e739dfac | 1425 | @cindex environment variable |
6de9cd9a DN |
1426 | |
1427 | @c man begin ENVIRONMENT | |
1428 | ||
7fc15ba5 | 1429 | The @command{gfortran} compiler currently does not make use of any environment |
6de9cd9a DN |
1430 | variables to control its operation above and beyond those |
1431 | that affect the operation of @command{gcc}. | |
1432 | ||
1433 | @xref{Environment Variables,,Environment Variables Affecting GCC, | |
1434 | gcc,Using the GNU Compiler Collection (GCC)}, for information on environment | |
1435 | variables. | |
1436 | ||
eaa90d25 | 1437 | @xref{Runtime}, for environment variables that affect the |
7fc15ba5 | 1438 | run-time behavior of programs compiled with GNU Fortran. |
6de9cd9a | 1439 | @c man end |