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fc1e05d2 | 1 | @c Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
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 | |
fc1e05d2 | 8 | Copyright @copyright{} 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
6de9cd9a DN |
9 | Free Software Foundation, Inc. |
10 | ||
11 | Permission is granted to copy, distribute and/or modify this document | |
07a67d6a | 12 | under the terms of the GNU Free Documentation License, Version 1.3 or |
6de9cd9a | 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}. | |
5a17346a SK |
137 | @gccoptlist{-fmax-errors=@var{n} |
138 | -fsyntax-only -pedantic -pedantic-errors -Wall @gol | |
139 | -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol | |
140 | -Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation @gol | |
141 | -Wintrinsics-std -Wreal-q-constant -Wsurprising -Wno-tabs -Wunderflow @gol | |
142 | -Wunused-parameter -Wintrinsic-shadow -Wno-align-commons @gol | |
143 | -Wfunction-elimination} | |
6de9cd9a DN |
144 | |
145 | @item Debugging Options | |
a2bef74c | 146 | @xref{Debugging Options,,Options for debugging your program or GNU Fortran}. |
1607a827 TK |
147 | @gccoptlist{-fdump-fortran-original -fdump-fortran-optimized @gol |
148 | -ffpe-trap=@var{list} -fdump-core -fbacktrace -fdump-parse-tree} | |
6de9cd9a DN |
149 | |
150 | @item Directory Options | |
a2bef74c | 151 | @xref{Directory Options,,Options for directory search}. |
d8ddea40 | 152 | @gccoptlist{-I@var{dir} -J@var{dir} -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 |
f4d1d50a | 169 | -fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol |
60386f50 | 170 | -fcoarray=@var{<none|single|lib>} -fmax-stack-var-size=@var{n} @gol |
c76f8d52 | 171 | -fstack-arrays @gol |
592600ce | 172 | -fpack-derived -frepack-arrays -fshort-enums -fexternal-blas @gol |
51b09ce3 | 173 | -fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol |
346a77d1 | 174 | -finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan|snan>} @gol |
72bd130e | 175 | -finit-logical=@var{<true|false>} -finit-character=@var{n} @gol |
51a30b32 TK |
176 | -fno-align-commons -fno-protect-parens -frealloc-lhs @gol |
177 | -faggressive-function-elimination -ffrontend-optimize} | |
6de9cd9a DN |
178 | @end table |
179 | ||
6de9cd9a DN |
180 | @menu |
181 | * Fortran Dialect Options:: Controlling the variant of Fortran language | |
182 | compiled. | |
670637ee | 183 | * Preprocessing Options:: Enable and customize preprocessing. |
592600ce | 184 | * Error and Warning Options:: How picky should the compiler be? |
6de9cd9a DN |
185 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. |
186 | * Directory Options:: Where to find module files | |
70263321 | 187 | * Link Options :: Influencing the linking step |
eaa90d25 | 188 | * Runtime Options:: Influencing runtime behavior |
6de9cd9a DN |
189 | * Code Gen Options:: Specifying conventions for function calls, data layout |
190 | and register usage. | |
191 | @end menu | |
192 | ||
193 | @node Fortran Dialect Options | |
a2bef74c | 194 | @section Options controlling Fortran dialect |
6de9cd9a DN |
195 | @cindex dialect options |
196 | @cindex language, dialect options | |
197 | @cindex options, dialect | |
198 | ||
3397327c BM |
199 | The following options control the details of the Fortran dialect |
200 | accepted by the compiler: | |
6de9cd9a DN |
201 | |
202 | @table @gcctabopt | |
4ba96c02 | 203 | @item -ffree-form |
4d04d67a | 204 | @itemx -ffixed-form |
32864778 DF |
205 | @opindex @code{ffree-form} |
206 | @opindex @code{fno-fixed-form} | |
207 | @cindex options, fortran dialect | |
e739dfac DF |
208 | @cindex file format, free |
209 | @cindex file format, fixed | |
49de9e73 | 210 | Specify the layout used by the source file. The free form layout |
6de9cd9a | 211 | was introduced in Fortran 90. Fixed form was traditionally used in |
3397327c BM |
212 | older Fortran programs. When neither option is specified, the source |
213 | form is determined by the file extension. | |
6de9cd9a | 214 | |
a23eec13 | 215 | @item -fall-intrinsics |
32864778 | 216 | @opindex @code{fall-intrinsics} |
aad9c4f4 AM |
217 | This option causes all intrinsic procedures (including the GNU-specific |
218 | extensions) to be accepted. This can be useful with @option{-std=f95} to | |
219 | force standard-compliance but get access to the full range of intrinsics | |
220 | available with @command{gfortran}. As a consequence, @option{-Wintrinsics-std} | |
221 | will be ignored and no user-defined procedure with the same name as any | |
222 | intrinsic will be called except when it is explicitly declared @code{EXTERNAL}. | |
a23eec13 | 223 | |
e0bcf78c | 224 | @item -fd-lines-as-code |
4d04d67a | 225 | @itemx -fd-lines-as-comments |
32864778 DF |
226 | @opindex @code{fd-lines-as-code} |
227 | @opindex @code{fd-lines-as-comments} | |
4ba96c02 | 228 | Enable special treatment for lines beginning with @code{d} or @code{D} |
3397327c BM |
229 | in fixed form sources. If the @option{-fd-lines-as-code} option is |
230 | given they are treated as if the first column contained a blank. If the | |
e0bcf78c TS |
231 | @option{-fd-lines-as-comments} option is given, they are treated as |
232 | comment lines. | |
233 | ||
3ae9eb27 | 234 | @item -fdefault-double-8 |
32864778 | 235 | @opindex @code{fdefault-double-8} |
aad9c4f4 AM |
236 | Set the @code{DOUBLE PRECISION} type to an 8 byte wide type. If |
237 | @option{-fdefault-real-8} is given, @code{DOUBLE PRECISION} would | |
238 | instead be promoted to 16 bytes if possible, and @option{-fdefault-double-8} | |
239 | can be used to prevent this. The kind of real constants like @code{1.d0} will | |
240 | not be changed by @option{-fdefault-real-8} though, so also | |
241 | @option{-fdefault-double-8} does not affect it. | |
3ae9eb27 | 242 | |
3ae9eb27 | 243 | @item -fdefault-integer-8 |
32864778 | 244 | @opindex @code{fdefault-integer-8} |
3ae9eb27 | 245 | Set the default integer and logical types to an 8 byte wide type. |
aad9c4f4 AM |
246 | Do nothing if this is already the default. This option also affects |
247 | the kind of integer constants like @code{42}. | |
3ae9eb27 | 248 | |
3ae9eb27 | 249 | @item -fdefault-real-8 |
32864778 | 250 | @opindex @code{fdefault-real-8} |
3ae9eb27 | 251 | Set the default real type to an 8 byte wide type. |
aad9c4f4 AM |
252 | Do nothing if this is already the default. This option also affects |
253 | the kind of non-double real constants like @code{1.0}, and does promote | |
254 | the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless | |
255 | @code{-fdefault-double-8} is given, too. | |
3ae9eb27 | 256 | |
6de9cd9a | 257 | @item -fdollar-ok |
32864778 | 258 | @opindex @code{fdollar-ok} |
ab940b73 | 259 | @cindex @code{$} |
6de9cd9a DN |
260 | @cindex symbol names |
261 | @cindex character set | |
f4a55802 DF |
262 | Allow @samp{$} as a valid non-first character in a symbol name. Symbols |
263 | that start with @samp{$} are rejected since it is unclear which rules to | |
cba2a54e | 264 | apply to implicit typing as different vendors implement different rules. |
6e8cb9be | 265 | Using @samp{$} in @code{IMPLICIT} statements is also rejected. |
6de9cd9a | 266 | |
4e6bf178 TB |
267 | @item -fbackslash |
268 | @opindex @code{backslash} | |
131c66cd FXC |
269 | @cindex backslash |
270 | @cindex escape characters | |
8fc541d3 FXC |
271 | Change the interpretation of backslashes in string literals from a single |
272 | backslash character to ``C-style'' escape characters. The following | |
273 | combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n}, | |
274 | @code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII | |
275 | characters alert, backspace, form feed, newline, carriage return, | |
276 | horizontal tab, vertical tab, backslash, and NUL, respectively. | |
277 | Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and | |
278 | @code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are | |
279 | translated into the Unicode characters corresponding to the specified code | |
280 | points. All other combinations of a character preceded by \ are | |
281 | unexpanded. | |
131c66cd | 282 | |
654b6073 FXC |
283 | @item -fmodule-private |
284 | @opindex @code{fmodule-private} | |
285 | @cindex module entities | |
286 | @cindex private | |
287 | Set the default accessibility of module entities to @code{PRIVATE}. | |
288 | Use-associated entities will not be accessible unless they are explicitly | |
289 | declared as @code{PUBLIC}. | |
290 | ||
6de9cd9a | 291 | @item -ffixed-line-length-@var{n} |
32864778 | 292 | @opindex @code{ffixed-line-length-}@var{n} |
e739dfac | 293 | @cindex file format, fixed |
6de9cd9a DN |
294 | Set column after which characters are ignored in typical fixed-form |
295 | lines in the source file, and through which spaces are assumed (as | |
296 | if padded to that length) after the ends of short fixed-form lines. | |
297 | ||
6de9cd9a | 298 | Popular values for @var{n} include 72 (the |
3397327c | 299 | standard and the default), 80 (card image), and 132 (corresponding |
6de9cd9a | 300 | to ``extended-source'' options in some popular compilers). |
3397327c | 301 | @var{n} may also be @samp{none}, meaning that the entire line is meaningful |
6de9cd9a DN |
302 | and that continued character constants never have implicit spaces appended |
303 | to them to fill out the line. | |
304 | @option{-ffixed-line-length-0} means the same thing as | |
305 | @option{-ffixed-line-length-none}. | |
306 | ||
16ab8e74 | 307 | @item -ffree-line-length-@var{n} |
32864778 | 308 | @opindex @code{ffree-line-length-}@var{n} |
e739dfac | 309 | @cindex file format, free |
16ab8e74 | 310 | Set column after which characters are ignored in typical free-form |
3397327c | 311 | lines in the source file. The default value is 132. |
16ab8e74 BF |
312 | @var{n} may be @samp{none}, meaning that the entire line is meaningful. |
313 | @option{-ffree-line-length-0} means the same thing as | |
314 | @option{-ffree-line-length-none}. | |
315 | ||
6de9cd9a | 316 | @item -fmax-identifier-length=@var{n} |
32864778 | 317 | @opindex @code{fmax-identifier-length=}@var{n} |
6de9cd9a | 318 | Specify the maximum allowed identifier length. Typical values are |
f489fba1 | 319 | 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008). |
6de9cd9a | 320 | |
6de9cd9a | 321 | @item -fimplicit-none |
32864778 | 322 | @opindex @code{fimplicit-none} |
6de9cd9a | 323 | Specify that no implicit typing is allowed, unless overridden by explicit |
40746dcc BM |
324 | @code{IMPLICIT} statements. This is the equivalent of adding |
325 | @code{implicit none} to the start of every procedure. | |
6de9cd9a | 326 | |
83d890b9 | 327 | @item -fcray-pointer |
32864778 | 328 | @opindex @code{fcray-pointer} |
3397327c BM |
329 | Enable the Cray pointer extension, which provides C-like pointer |
330 | functionality. | |
83d890b9 | 331 | |
6c7a4dfd | 332 | @item -fopenmp |
32864778 | 333 | @opindex @code{fopenmp} |
4e8b3590 | 334 | @cindex OpenMP |
3397327c BM |
335 | Enable the OpenMP extensions. This includes OpenMP @code{!$omp} directives |
336 | in free form | |
6c7a4dfd | 337 | and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form, |
3397327c BM |
338 | @code{!$} conditional compilation sentinels in free form |
339 | and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form, | |
6c7a4dfd | 340 | and when linking arranges for the OpenMP runtime library to be linked |
1e7de83b | 341 | in. The option @option{-fopenmp} implies @option{-frecursive}. |
6c7a4dfd | 342 | |
200c5036 | 343 | @item -fno-range-check |
32864778 | 344 | @opindex @code{frange-check} |
200c5036 | 345 | Disable range checking on results of simplification of constant |
a84b9ee8 SK |
346 | expressions during compilation. For example, GNU Fortran will give |
347 | an error at compile time when simplifying @code{a = 1. / 0}. | |
348 | With this option, no error will be given and @code{a} will be assigned | |
349 | the value @code{+Infinity}. If an expression evaluates to a value | |
350 | outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}], | |
351 | then the expression will be replaced by @code{-Inf} or @code{+Inf} | |
352 | as appropriate. | |
40746dcc BM |
353 | Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow |
354 | on most systems, but with @option{-fno-range-check} the value will | |
355 | ``wrap around'' and @code{i} will be initialized to @math{-1} instead. | |
54554825 | 356 | |
6de9cd9a | 357 | @item -std=@var{std} |
32864778 | 358 | @opindex @code{std=}@var{std} option |
276419d0 | 359 | Specify the standard to which the program is expected to conform, which |
f489fba1 FXC |
360 | may be one of @samp{f95}, @samp{f2003}, @samp{f2008}, @samp{gnu}, or |
361 | @samp{legacy}. The default value for @var{std} is @samp{gnu}, which | |
362 | specifies a superset of the Fortran 95 standard that includes all of the | |
363 | extensions supported by GNU Fortran, although warnings will be given for | |
364 | obsolete extensions not recommended for use in new code. The | |
365 | @samp{legacy} value is equivalent but without the warnings for obsolete | |
366 | extensions, and may be useful for old non-standard programs. The | |
367 | @samp{f95}, @samp{f2003} and @samp{f2008} values specify strict | |
368 | conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards, | |
369 | respectively; errors are given for all extensions beyond the relevant | |
370 | language standard, and warnings are given for the Fortran 77 features | |
2e8d9212 TB |
371 | that are permitted but obsolescent in later standards. @samp{-std=f2008tr} |
372 | allows the Fortran 2008 standard including the additions of the | |
373 | technical report (TR) 29113. | |
6de9cd9a | 374 | |
6de9cd9a DN |
375 | @end table |
376 | ||
670637ee DF |
377 | @node Preprocessing Options |
378 | @section Enable and customize preprocessing | |
379 | @cindex preprocessor | |
380 | @cindex options, preprocessor | |
381 | @cindex CPP | |
382 | ||
383 | Preprocessor related options. See section | |
384 | @ref{Preprocessing and conditional compilation} for more detailed | |
385 | information on preprocessing in @command{gfortran}. | |
386 | ||
387 | @table @gcctabopt | |
388 | @item -cpp | |
4d04d67a | 389 | @itemx -nocpp |
670637ee DF |
390 | @opindex @code{cpp} |
391 | @opindex @code{fpp} | |
392 | @cindex preprocessor, enable | |
393 | @cindex preprocessor, disable | |
394 | Enable preprocessing. The preprocessor is automatically invoked if | |
395 | the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR}, | |
396 | @file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use | |
397 | this option to manually enable preprocessing of any kind of Fortran file. | |
398 | ||
399 | To disable preprocessing of files with any of the above listed extensions, | |
400 | use the negative form: @option{-nocpp}. | |
401 | ||
f90b55a6 TK |
402 | The preprocessor is run in traditional mode. Any restrictions of the |
403 | file-format, especially the limits on line length, apply for | |
404 | preprocessed output as well, so it might be advisable to use the | |
405 | @option{-ffree-line-length-none} or @option{-ffixed-line-length-none} | |
406 | options. | |
670637ee DF |
407 | |
408 | @item -dM | |
409 | @opindex @code{dM} | |
410 | @cindex preprocessor, debugging | |
411 | @cindex debugging, preprocessor | |
412 | Instead of the normal output, generate a list of @code{'#define'} | |
413 | directives for all the macros defined during the execution of the | |
414 | preprocessor, including predefined macros. This gives you a way | |
415 | of finding out what is predefined in your version of the preprocessor. | |
416 | Assuming you have no file @file{foo.f90}, the command | |
417 | @smallexample | |
fc1e05d2 | 418 | touch foo.f90; gfortran -cpp -E -dM foo.f90 |
670637ee DF |
419 | @end smallexample |
420 | will show all the predefined macros. | |
421 | ||
422 | @item -dD | |
423 | @opindex @code{dD} | |
424 | @cindex preprocessor, debugging | |
425 | @cindex debugging, preprocessor | |
426 | Like @option{-dM} except in two respects: it does not include the | |
427 | predefined macros, and it outputs both the @code{#define} directives | |
428 | and the result of preprocessing. Both kinds of output go to the | |
429 | standard output file. | |
430 | ||
431 | @item -dN | |
432 | @opindex @code{dN} | |
433 | @cindex preprocessor, debugging | |
434 | @cindex debugging, preprocessor | |
435 | Like @option{-dD}, but emit only the macro names, not their expansions. | |
436 | ||
437 | @item -dU | |
438 | @opindex @code{dU} | |
439 | @cindex preprocessor, debugging | |
440 | @cindex debugging, preprocessor | |
441 | Like @option{dD} except that only macros that are expanded, or whose | |
442 | definedness is tested in preprocessor directives, are output; the | |
443 | output is delayed until the use or test of the macro; and @code{'#undef'} | |
444 | directives are also output for macros tested but undefined at the time. | |
445 | ||
446 | @item -dI | |
447 | @opindex @code{dI} | |
448 | @cindex preprocessor, debugging | |
449 | @cindex debugging, preprocessor | |
450 | Output @code{'#include'} directives in addition to the result | |
451 | of preprocessing. | |
452 | ||
453 | @item -fworking-directory | |
454 | @opindex @code{fworking-directory} | |
455 | @cindex preprocessor, working directory | |
456 | Enable generation of linemarkers in the preprocessor output that will | |
457 | let the compiler know the current working directory at the time of | |
458 | preprocessing. When this option is enabled, the preprocessor will emit, | |
459 | after the initial linemarker, a second linemarker with the current | |
460 | working directory followed by two slashes. GCC will use this directory, | |
461 | when it's present in the preprocessed input, as the directory emitted | |
462 | as the current working directory in some debugging information formats. | |
463 | This option is implicitly enabled if debugging information is enabled, | |
464 | but this can be inhibited with the negated form | |
465 | @option{-fno-working-directory}. If the @option{-P} flag is present | |
466 | in the command line, this option has no effect, since no @code{#line} | |
467 | directives are emitted whatsoever. | |
468 | ||
c3280643 DF |
469 | @item -idirafter @var{dir} |
470 | @opindex @code{idirafter @var{dir}} | |
471 | @cindex preprocessing, include path | |
472 | Search @var{dir} for include files, but do it after all directories | |
473 | specified with @option{-I} and the standard system directories have | |
474 | been exhausted. @var{dir} is treated as a system include directory. | |
475 | If dir begins with @code{=}, then the @code{=} will be replaced by | |
476 | the sysroot prefix; see @option{--sysroot} and @option{-isysroot}. | |
477 | ||
670637ee DF |
478 | @item -imultilib @var{dir} |
479 | @opindex @code{imultilib @var{dir}} | |
480 | @cindex preprocessing, include path | |
481 | Use @var{dir} as a subdirectory of the directory containing target-specific | |
482 | C++ headers. | |
483 | ||
484 | @item -iprefix @var{prefix} | |
485 | @opindex @code{iprefix @var{prefix}} | |
486 | @cindex preprocessing, include path | |
487 | Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix} | |
488 | options. If the @var{prefix} represents a directory, you should include | |
489 | the final @code{'/'}. | |
490 | ||
491 | @item -isysroot @var{dir} | |
492 | @opindex @code{isysroot @var{dir}} | |
493 | @cindex preprocessing, include path | |
494 | This option is like the @option{--sysroot} option, but applies only to | |
495 | header files. See the @option{--sysroot} option for more information. | |
496 | ||
497 | @item -iquote @var{dir} | |
498 | @opindex @code{iquote @var{dir}} | |
499 | @cindex preprocessing, include path | |
500 | Search @var{dir} only for header files requested with @code{#include "file"}; | |
501 | they are not searched for @code{#include <file>}, before all directories | |
502 | specified by @option{-I} and before the standard system directories. If | |
503 | @var{dir} begins with @code{=}, then the @code{=} will be replaced by the | |
504 | sysroot prefix; see @option{--sysroot} and @option{-isysroot}. | |
505 | ||
506 | @item -isystem @var{dir} | |
507 | @opindex @code{isystem @var{dir}} | |
508 | @cindex preprocessing, include path | |
509 | Search @var{dir} for header files, after all directories specified by | |
510 | @option{-I} but before the standard system directories. Mark it as a | |
511 | system directory, so that it gets the same special treatment as is | |
512 | applied to the standard system directories. If @var{dir} begins with | |
513 | @code{=}, then the @code{=} will be replaced by the sysroot prefix; | |
514 | see @option{--sysroot} and @option{-isysroot}. | |
515 | ||
516 | @item -nostdinc | |
517 | @opindex @code{nostdinc} | |
518 | Do not search the standard system directories for header files. Only | |
519 | the directories you have specified with @option{-I} options (and the | |
520 | directory of the current file, if appropriate) are searched. | |
521 | ||
522 | @item -undef | |
523 | @opindex @code{undef} | |
524 | Do not predefine any system-specific or GCC-specific macros. | |
525 | The standard predefined macros remain defined. | |
526 | ||
527 | @item -A@var{predicate}=@var{answer} | |
528 | @opindex @code{A@var{predicate}=@var{answer}} | |
4d04d67a | 529 | @cindex preprocessing, assertion |
670637ee DF |
530 | Make an assertion with the predicate @var{predicate} and answer @var{answer}. |
531 | This form is preferred to the older form -A predicate(answer), which is still | |
532 | supported, because it does not use shell special characters. | |
533 | ||
534 | @item -A-@var{predicate}=@var{answer} | |
535 | @opindex @code{A-@var{predicate}=@var{answer}} | |
4d04d67a | 536 | @cindex preprocessing, assertion |
670637ee DF |
537 | Cancel an assertion with the predicate @var{predicate} and answer @var{answer}. |
538 | ||
539 | @item -C | |
540 | @opindex @code{C} | |
541 | @cindex preprocessing, keep comments | |
542 | Do not discard comments. All comments are passed through to the output | |
543 | file, except for comments in processed directives, which are deleted | |
544 | along with the directive. | |
545 | ||
546 | You should be prepared for side effects when using @option{-C}; it causes | |
547 | the preprocessor to treat comments as tokens in their own right. For example, | |
548 | comments appearing at the start of what would be a directive line have the | |
549 | effect of turning that line into an ordinary source line, since the first | |
550 | token on the line is no longer a @code{'#'}. | |
551 | ||
552 | Warning: this currently handles C-Style comments only. The preprocessor | |
553 | does not yet recognize Fortran-style comments. | |
554 | ||
555 | @item -CC | |
556 | @opindex @code{CC} | |
557 | @cindex preprocessing, keep comments | |
558 | Do not discard comments, including during macro expansion. This is like | |
559 | @option{-C}, except that comments contained within macros are also passed | |
560 | through to the output file where the macro is expanded. | |
561 | ||
562 | In addition to the side-effects of the @option{-C} option, the @option{-CC} | |
563 | option causes all C++-style comments inside a macro to be converted to C-style | |
564 | comments. This is to prevent later use of that macro from inadvertently | |
565 | commenting out the remainder of the source line. The @option{-CC} option | |
566 | is generally used to support lint comments. | |
567 | ||
568 | Warning: this currently handles C- and C++-Style comments only. The | |
569 | preprocessor does not yet recognize Fortran-style comments. | |
570 | ||
571 | @item -D@var{name} | |
572 | @opindex @code{D@var{name}} | |
573 | @cindex preprocessing, define macros | |
574 | Predefine name as a macro, with definition @code{1}. | |
575 | ||
576 | @item -D@var{name}=@var{definition} | |
577 | @opindex @code{D@var{name}=@var{definition}} | |
578 | @cindex preprocessing, define macros | |
579 | The contents of @var{definition} are tokenized and processed as if they | |
580 | appeared during translation phase three in a @code{'#define'} directive. | |
581 | In particular, the definition will be truncated by embedded newline | |
582 | characters. | |
583 | ||
584 | If you are invoking the preprocessor from a shell or shell-like program | |
585 | you may need to use the shell's quoting syntax to protect characters such | |
586 | as spaces that have a meaning in the shell syntax. | |
587 | ||
588 | If you wish to define a function-like macro on the command line, write | |
589 | its argument list with surrounding parentheses before the equals sign | |
590 | (if any). Parentheses are meaningful to most shells, so you will need | |
591 | to quote the option. With sh and csh, @code{-D'name(args...)=definition'} | |
592 | works. | |
593 | ||
594 | @option{-D} and @option{-U} options are processed in the order they are | |
595 | given on the command line. All -imacros file and -include file options | |
596 | are processed after all -D and -U options. | |
597 | ||
598 | @item -H | |
599 | @opindex @code{H} | |
600 | Print the name of each header file used, in addition to other normal | |
601 | activities. Each name is indented to show how deep in the @code{'#include'} | |
602 | stack it is. | |
603 | ||
604 | @item -P | |
605 | @opindex @code{P} | |
606 | @cindex preprocessing, no linemarkers | |
607 | Inhibit generation of linemarkers in the output from the preprocessor. | |
608 | This might be useful when running the preprocessor on something that | |
609 | is not C code, and will be sent to a program which might be confused | |
610 | by the linemarkers. | |
611 | ||
612 | @item -U@var{name} | |
613 | @opindex @code{U@var{name}} | |
614 | @cindex preprocessing, undefine macros | |
615 | Cancel any previous definition of @var{name}, either built in or provided | |
616 | with a @option{-D} option. | |
617 | @end table | |
618 | ||
619 | ||
592600ce | 620 | @node Error and Warning Options |
a2bef74c | 621 | @section Options to request or suppress errors and warnings |
6de9cd9a | 622 | @cindex options, warnings |
592600ce | 623 | @cindex options, errors |
6de9cd9a | 624 | @cindex warnings, suppressing |
592600ce | 625 | @cindex messages, error |
6de9cd9a DN |
626 | @cindex messages, warning |
627 | @cindex suppressing warnings | |
628 | ||
592600ce BM |
629 | Errors are diagnostic messages that report that the GNU Fortran compiler |
630 | cannot compile the relevant piece of source code. The compiler will | |
631 | continue to process the program in an attempt to report further errors | |
632 | to aid in debugging, but will not produce any compiled output. | |
633 | ||
6de9cd9a | 634 | Warnings are diagnostic messages that report constructions which |
592600ce | 635 | are not inherently erroneous but which are risky or suggest there is |
4ba96c02 | 636 | likely to be a bug in the program. Unless @option{-Werror} is specified, |
592600ce | 637 | they do not prevent compilation of the program. |
6de9cd9a DN |
638 | |
639 | You can request many specific warnings with options beginning @option{-W}, | |
640 | for example @option{-Wimplicit} to request warnings on implicit | |
641 | declarations. Each of these specific warning options also has a | |
642 | negative form beginning @option{-Wno-} to turn off warnings; | |
643 | for example, @option{-Wno-implicit}. This manual lists only one of the | |
644 | two forms, whichever is not the default. | |
645 | ||
592600ce BM |
646 | These options control the amount and kinds of errors and warnings produced |
647 | by GNU Fortran: | |
6de9cd9a DN |
648 | |
649 | @table @gcctabopt | |
efb66586 JD |
650 | @item -fmax-errors=@var{n} |
651 | @opindex @code{fmax-errors=}@var{n} | |
4ba96c02 | 652 | @cindex errors, limiting |
592600ce BM |
653 | Limits the maximum number of error messages to @var{n}, at which point |
654 | GNU Fortran bails out rather than attempting to continue processing the | |
655 | source code. If @var{n} is 0, there is no limit on the number of error | |
656 | messages produced. | |
657 | ||
6de9cd9a | 658 | @item -fsyntax-only |
32864778 | 659 | @opindex @code{fsyntax-only} |
4ba96c02 | 660 | @cindex syntax checking |
adeb22c4 FXC |
661 | Check the code for syntax errors, but don't actually compile it. This |
662 | will generate module files for each module present in the code, but no | |
663 | other output file. | |
6de9cd9a | 664 | |
6de9cd9a | 665 | @item -pedantic |
32864778 | 666 | @opindex @code{pedantic} |
7fc15ba5 | 667 | Issue warnings for uses of extensions to Fortran 95. |
6de9cd9a DN |
668 | @option{-pedantic} also applies to C-language constructs where they |
669 | occur in GNU Fortran source files, such as use of @samp{\e} in a | |
40746dcc | 670 | character constant within a directive like @code{#include}. |
6de9cd9a | 671 | |
7fc15ba5 | 672 | Valid Fortran 95 programs should compile properly with or without |
6de9cd9a DN |
673 | this option. |
674 | However, without this option, certain GNU extensions and traditional | |
675 | Fortran features are supported as well. | |
676 | With this option, many of them are rejected. | |
677 | ||
678 | Some users try to use @option{-pedantic} to check programs for conformance. | |
679 | They soon find that it does not do quite what they want---it finds some | |
680 | nonstandard practices, but not all. | |
7fc15ba5 | 681 | However, improvements to GNU Fortran in this area are welcome. |
6de9cd9a | 682 | |
f489fba1 FXC |
683 | This should be used in conjunction with @option{-std=f95}, |
684 | @option{-std=f2003} or @option{-std=f2008}. | |
6de9cd9a | 685 | |
6de9cd9a | 686 | @item -pedantic-errors |
32864778 | 687 | @opindex @code{pedantic-errors} |
6de9cd9a DN |
688 | Like @option{-pedantic}, except that errors are produced rather than |
689 | warnings. | |
690 | ||
6de9cd9a | 691 | @item -Wall |
32864778 | 692 | @opindex @code{Wall} |
6de9cd9a DN |
693 | @cindex all warnings |
694 | @cindex warnings, all | |
3fbab549 JD |
695 | Enables commonly used warning options pertaining to usage that |
696 | we recommend avoiding and that we believe are easy to avoid. | |
daf8c6f0 DF |
697 | This currently includes @option{-Waliasing}, @option{-Wampersand}, |
698 | @option{-Wconversion}, @option{-Wsurprising}, @option{-Wintrinsics-std}, | |
4ed44ccc | 699 | @option{-Wno-tabs}, @option{-Wintrinsic-shadow}, @option{-Wline-truncation}, |
5a17346a | 700 | @option{-Wreal-q-constant} and @option{-Wunused}. |
6de9cd9a | 701 | |
6de9cd9a | 702 | @item -Waliasing |
32864778 | 703 | @opindex @code{Waliasing} |
6de9cd9a | 704 | @cindex aliasing |
32864778 | 705 | @cindex warnings, aliasing |
3010be13 AD |
706 | Warn about possible aliasing of dummy arguments. Specifically, it warns |
707 | if the same actual argument is associated with a dummy argument with | |
40746dcc | 708 | @code{INTENT(IN)} and a dummy argument with @code{INTENT(OUT)} in a call |
3010be13 AD |
709 | with an explicit interface. |
710 | ||
711 | The following example will trigger the warning. | |
6de9cd9a | 712 | @smallexample |
3010be13 AD |
713 | interface |
714 | subroutine bar(a,b) | |
715 | integer, intent(in) :: a | |
716 | integer, intent(out) :: b | |
717 | end subroutine | |
718 | end interface | |
719 | integer :: a | |
720 | ||
721 | call bar(a,a) | |
6de9cd9a DN |
722 | @end smallexample |
723 | ||
3fbab549 | 724 | @item -Wampersand |
32864778 DF |
725 | @opindex @code{Wampersand} |
726 | @cindex warnings, ampersand | |
ab940b73 | 727 | @cindex @code{&} |
3fbab549 | 728 | Warn about missing ampersand in continued character constants. The warning is |
f489fba1 FXC |
729 | given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95}, |
730 | @option{-std=f2003} and @option{-std=f2008}. Note: With no ampersand | |
731 | given in a continued character constant, GNU Fortran assumes continuation | |
732 | at the first non-comment, non-whitespace character after the ampersand | |
733 | that initiated the continuation. | |
3fbab549 | 734 | |
bdfd2ff0 TK |
735 | @item -Warray-temporaries |
736 | @opindex @code{Warray-temporaries} | |
737 | @cindex warnings, array temporaries | |
738 | Warn about array temporaries generated by the compiler. The information | |
739 | generated by this warning is sometimes useful in optimization, in order to | |
740 | avoid such temporaries. | |
741 | ||
276419d0 | 742 | @item -Wcharacter-truncation |
32864778 DF |
743 | @opindex @code{Wcharacter-truncation} |
744 | @cindex warnings, character truncation | |
276419d0 BM |
745 | Warn when a character assignment will truncate the assigned string. |
746 | ||
802e3f8c RW |
747 | @item -Wline-truncation |
748 | @opindex @code{Wline-truncation} | |
749 | @cindex warnings, line truncation | |
750 | Warn when a source code line will be truncated. | |
751 | ||
6de9cd9a | 752 | @item -Wconversion |
32864778 DF |
753 | @opindex @code{Wconversion} |
754 | @cindex warnings, conversion | |
6de9cd9a | 755 | @cindex conversion |
daf8c6f0 DF |
756 | Warn about implicit conversions that are likely to change the value of |
757 | the expression after conversion. Implied by @option{-Wall}. | |
758 | ||
759 | @item -Wconversion-extra | |
760 | @opindex @code{Wconversion-extra} | |
761 | @cindex warnings, conversion | |
762 | @cindex conversion | |
763 | Warn about implicit conversions between different types and kinds. | |
6de9cd9a | 764 | |
6de9cd9a | 765 | @item -Wimplicit-interface |
32864778 DF |
766 | @opindex @code{Wimplicit-interface} |
767 | @cindex warnings, implicit interface | |
02712c16 | 768 | Warn if a procedure is called without an explicit interface. |
6de9cd9a DN |
769 | Note this only checks that an explicit interface is present. It does not |
770 | check that the declared interfaces are consistent across program units. | |
771 | ||
ca071303 FXC |
772 | @item -Wimplicit-procedure |
773 | @opindex @code{Wimplicit-procedure} | |
774 | @cindex warnings, implicit procedure | |
775 | Warn if a procedure is called that has neither an explicit interface | |
776 | nor has been declared as @code{EXTERNAL}. | |
777 | ||
c3005b0f DK |
778 | @item -Wintrinsics-std |
779 | @opindex @code{Wintrinsics-std} | |
1207ac67 | 780 | @cindex warnings, non-standard intrinsics |
c3005b0f DK |
781 | @cindex warnings, intrinsics of other standards |
782 | Warn if @command{gfortran} finds a procedure named like an intrinsic not | |
783 | available in the currently selected standard (with @option{-std}) and treats | |
784 | it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can | |
c7d9f803 | 785 | be used to never trigger this behavior and always link to the intrinsic |
c3005b0f | 786 | regardless of the selected standard. |
b7892582 | 787 | |
5a17346a SK |
788 | @item -Wreal-q-constant |
789 | @opindex @code{Wreal-q-constant} | |
790 | @cindex warnings, @code{q} exponent-letter | |
791 | Produce a warning if a real-literal-constant contains a @code{q} | |
792 | exponent-letter. | |
793 | ||
6de9cd9a | 794 | @item -Wsurprising |
32864778 DF |
795 | @opindex @code{Wsurprising} |
796 | @cindex warnings, suspicious code | |
2d8b59df SK |
797 | Produce a warning when ``suspicious'' code constructs are encountered. |
798 | While technically legal these usually indicate that an error has been made. | |
6de9cd9a DN |
799 | |
800 | This currently produces a warning under the following circumstances: | |
801 | ||
802 | @itemize @bullet | |
803 | @item | |
ffd1953e FXC |
804 | An INTEGER SELECT construct has a CASE that can never be matched as its |
805 | lower value is greater than its upper value. | |
6de9cd9a DN |
806 | |
807 | @item | |
808 | A LOGICAL SELECT construct has three CASE statements. | |
39a184ce JD |
809 | |
810 | @item | |
811 | A TRANSFER specifies a source that is shorter than the destination. | |
fee3292b DK |
812 | |
813 | @item | |
814 | The type of a function result is declared more than once with the same type. If | |
815 | @option{-pedantic} or standard-conforming mode is enabled, this is an error. | |
5e1d6b4c DK |
816 | |
817 | @item | |
818 | A @code{CHARACTER} variable is declared with negative length. | |
6de9cd9a DN |
819 | @end itemize |
820 | ||
840bd9f7 | 821 | @item -Wtabs |
32864778 DF |
822 | @opindex @code{Wtabs} |
823 | @cindex warnings, tabs | |
e739dfac | 824 | @cindex tabulators |
840bd9f7 | 825 | By default, tabs are accepted as whitespace, but tabs are not members |
fd1935d5 TB |
826 | of the Fortran Character Set. For continuation lines, a tab followed |
827 | by a digit between 1 and 9 is supported. @option{-Wno-tabs} will cause | |
828 | a warning to be issued if a tab is encountered. Note, @option{-Wno-tabs} | |
829 | is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003}, | |
f489fba1 | 830 | @option{-std=f2008} and @option{-Wall}. |
840bd9f7 | 831 | |
2d8b59df | 832 | @item -Wunderflow |
32864778 DF |
833 | @opindex @code{Wunderflow} |
834 | @cindex warnings, underflow | |
835 | @cindex underflow | |
2d8b59df SK |
836 | Produce a warning when numerical constant expressions are |
837 | encountered, which yield an UNDERFLOW during compilation. | |
838 | ||
c3005b0f DK |
839 | @item -Wintrinsic-shadow |
840 | @opindex @code{Wintrinsic-shadow} | |
841 | @cindex warnings, intrinsic | |
842 | @cindex intrinsic | |
843 | Warn if a user-defined procedure or module procedure has the same name as an | |
844 | intrinsic; in this case, an explicit interface or @code{EXTERNAL} or | |
845 | @code{INTRINSIC} declaration might be needed to get calls later resolved to | |
846 | the desired intrinsic/procedure. | |
847 | ||
4ed44ccc DF |
848 | @item -Wunused-dummy-argument |
849 | @opindex @code{Wunused-dummy-argument} | |
850 | @cindex warnings, unused dummy argument | |
851 | @cindex unused dummy argument | |
852 | @cindex dummy argument, unused | |
853 | Warn about unused dummy arguments. This option is implied by @option{-Wall}. | |
854 | ||
d92693b4 DF |
855 | @item -Wunused-parameter |
856 | @opindex @code{Wunused-parameter} | |
857 | @cindex warnings, unused parameter | |
858 | @cindex unused parameter | |
859 | Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter}, | |
860 | @command{gfortran}'s implementation of this option does not warn | |
4ed44ccc DF |
861 | about unused dummy arguments (see @option{-Wunused-dummy-argument}), |
862 | but about unused @code{PARAMETER} values. @option{-Wunused-parameter} | |
863 | is not included in @option{-Wall} but is implied by @option{-Wall -Wextra}. | |
d92693b4 | 864 | |
f613cea7 JW |
865 | @item -Walign-commons |
866 | @opindex @code{Walign-commons} | |
ab940b73 RW |
867 | @cindex warnings, alignment of @code{COMMON} blocks |
868 | @cindex alignment of @code{COMMON} blocks | |
f613cea7 | 869 | By default, @command{gfortran} warns about any occasion of variables being |
ab940b73 | 870 | padded for proper alignment inside a @code{COMMON} block. This warning can be turned |
f613cea7 JW |
871 | off via @option{-Wno-align-commons}. See also @option{-falign-commons}. |
872 | ||
51a30b32 TK |
873 | @item -Wfunction-elimination |
874 | @opindex @code{Wfunction-elimination} | |
875 | @cindex function elimination | |
876 | @cindex warnings, function elimination | |
877 | Warn if any calls to functions are eliminated by the optimizations | |
878 | enabled by the @option{-ffrontend-optimize} option. | |
879 | ||
880 | ||
6de9cd9a | 881 | @item -Werror |
32864778 DF |
882 | @opindex @code{Werror} |
883 | @cindex warnings, to errors | |
6de9cd9a | 884 | Turns all warnings into errors. |
6de9cd9a DN |
885 | @end table |
886 | ||
4f7d9db8 | 887 | @xref{Warning Options,,Options to Request or Suppress Errors and |
592600ce BM |
888 | Warnings, gcc,Using the GNU Compiler Collection (GCC)}, for information on |
889 | more options offered by the GBE shared by @command{gfortran}, @command{gcc} | |
890 | and other GNU compilers. | |
6de9cd9a DN |
891 | |
892 | Some of these have no effect when compiling programs written in Fortran. | |
893 | ||
894 | @node Debugging Options | |
a2bef74c | 895 | @section Options for debugging your program or GNU Fortran |
6de9cd9a DN |
896 | @cindex options, debugging |
897 | @cindex debugging information options | |
898 | ||
899 | GNU Fortran has various special options that are used for debugging | |
7fc15ba5 | 900 | either your program or the GNU Fortran compiler. |
6de9cd9a DN |
901 | |
902 | @table @gcctabopt | |
1607a827 TK |
903 | @item -fdump-fortran-original |
904 | @opindex @code{fdump-fortran-original} | |
905 | Output the internal parse tree after translating the source program | |
906 | into internal representation. Only really useful for debugging the | |
907 | GNU Fortran compiler itself. | |
908 | ||
909 | @item -fdump-optimized-tree | |
910 | @opindex @code{fdump-fortran-optimized} | |
911 | Output the parse tree after front-end optimization. Only really | |
912 | useful for debugging the GNU Fortran compiler itself. | |
913 | ||
32864778 | 914 | @opindex @code{fdump-parse-tree} |
1607a827 TK |
915 | Output the internal parse tree after translating the source program |
916 | into internal representation. Only really useful for debugging the | |
917 | GNU Fortran compiler itself. This option is deprecated; use | |
918 | @code{-fdump-fortran-original} instead. | |
6de9cd9a | 919 | |
944b8b35 | 920 | @item -ffpe-trap=@var{list} |
32864778 | 921 | @opindex @code{ffpe-trap=}@var{list} |
944b8b35 FXC |
922 | Specify a list of IEEE exceptions when a Floating Point Exception |
923 | (FPE) should be raised. On most systems, this will result in a SIGFPE | |
924 | signal being sent and the program being interrupted, producing a core | |
925 | file useful for debugging. @var{list} is a (possibly empty) comma-separated | |
926 | list of the following IEEE exceptions: @samp{invalid} (invalid floating | |
40746dcc | 927 | point operation, such as @code{SQRT(-1.0)}), @samp{zero} (division by |
944b8b35 FXC |
928 | zero), @samp{overflow} (overflow in a floating point operation), |
929 | @samp{underflow} (underflow in a floating point operation), | |
930 | @samp{precision} (loss of precision during operation) and @samp{denormal} | |
27ea0360 | 931 | (operation produced a denormal value). |
eedeea04 | 932 | |
8307c61b | 933 | Some of the routines in the Fortran runtime library, like |
aad9c4f4 | 934 | @samp{CPU_TIME}, are likely to trigger floating point exceptions when |
8307c61b FXC |
935 | @code{ffpe-trap=precision} is used. For this reason, the use of |
936 | @code{ffpe-trap=precision} is not recommended. | |
937 | ||
868d75db | 938 | @item -fbacktrace |
32864778 | 939 | @opindex @code{fbacktrace} |
868d75db FXC |
940 | @cindex backtrace |
941 | @cindex trace | |
2b840e50 FXC |
942 | Specify that, when a runtime error is encountered or a deadly signal is |
943 | emitted (segmentation fault, illegal instruction, bus error or | |
944 | floating-point exception), the Fortran runtime | |
868d75db FXC |
945 | library should output a backtrace of the error. This option |
946 | only has influence for compilation of the Fortran main program. | |
947 | ||
eedeea04 | 948 | @item -fdump-core |
e739dfac DF |
949 | @cindex core, dump |
950 | @opindex @code{fdump-core} | |
eedeea04 FXC |
951 | Request that a core-dump file is written to disk when a runtime error |
952 | is encountered on systems that support core dumps. This option is | |
953 | only effective for the compilation of the Fortran main program. | |
944b8b35 FXC |
954 | @end table |
955 | ||
6de9cd9a DN |
956 | @xref{Debugging Options,,Options for Debugging Your Program or GCC, |
957 | gcc,Using the GNU Compiler Collection (GCC)}, for more information on | |
958 | debugging options. | |
959 | ||
960 | @node Directory Options | |
a2bef74c | 961 | @section Options for directory search |
6de9cd9a DN |
962 | @cindex directory, options |
963 | @cindex options, directory search | |
964 | @cindex search path | |
ab940b73 RW |
965 | @cindex @code{INCLUDE} directive |
966 | @cindex directive, @code{INCLUDE} | |
7fc15ba5 | 967 | These options affect how GNU Fortran searches |
5724da63 | 968 | for files specified by the @code{INCLUDE} directive and where it searches |
6de9cd9a DN |
969 | for previously compiled modules. |
970 | ||
971 | It also affects the search paths used by @command{cpp} when used to preprocess | |
2d8b59df | 972 | Fortran source. |
6de9cd9a DN |
973 | |
974 | @table @gcctabopt | |
6de9cd9a | 975 | @item -I@var{dir} |
32864778 | 976 | @opindex @code{I}@var{dir} |
6de9cd9a DN |
977 | @cindex directory, search paths for inclusion |
978 | @cindex inclusion, directory search paths for | |
979 | @cindex search paths, for included files | |
980 | @cindex paths, search | |
981 | @cindex module search path | |
982 | These affect interpretation of the @code{INCLUDE} directive | |
983 | (as well as of the @code{#include} directive of the @command{cpp} | |
984 | preprocessor). | |
985 | ||
986 | Also note that the general behavior of @option{-I} and | |
987 | @code{INCLUDE} is pretty much the same as of @option{-I} with | |
988 | @code{#include} in the @command{cpp} preprocessor, with regard to | |
989 | looking for @file{header.gcc} files and other such things. | |
990 | ||
40746dcc | 991 | This path is also used to search for @file{.mod} files when previously |
6de9cd9a DN |
992 | compiled modules are required by a @code{USE} statement. |
993 | ||
994 | @xref{Directory Options,,Options for Directory Search, | |
995 | gcc,Using the GNU Compiler Collection (GCC)}, for information on the | |
996 | @option{-I} option. | |
997 | ||
6de9cd9a | 998 | @item -J@var{dir} |
32864778 | 999 | @opindex @code{J}@var{dir} |
ccc2ed87 | 1000 | @opindex @code{M}@var{dir} |
276419d0 BM |
1001 | @cindex paths, search |
1002 | @cindex module search path | |
40746dcc | 1003 | This option specifies where to put @file{.mod} files for compiled modules. |
2d8b59df | 1004 | It is also added to the list of directories to searched by an @code{USE} |
6de9cd9a DN |
1005 | statement. |
1006 | ||
1007 | The default is the current directory. | |
1008 | ||
276419d0 | 1009 | @item -fintrinsic-modules-path @var{dir} |
32864778 | 1010 | @opindex @code{fintrinsic-modules-path} @var{dir} |
276419d0 BM |
1011 | @cindex paths, search |
1012 | @cindex module search path | |
1013 | This option specifies the location of pre-compiled intrinsic modules, if | |
1014 | they are not in the default location expected by the compiler. | |
6de9cd9a DN |
1015 | @end table |
1016 | ||
70263321 | 1017 | @node Link Options |
a2bef74c | 1018 | @section Influencing the linking step |
70263321 DF |
1019 | @cindex options, linking |
1020 | @cindex linking, static | |
1021 | ||
1022 | These options come into play when the compiler links object files into an | |
1023 | executable output file. They are meaningless if the compiler is not doing | |
1024 | a link step. | |
1025 | ||
1026 | @table @gcctabopt | |
1027 | @item -static-libgfortran | |
1028 | @opindex @code{static-libgfortran} | |
1029 | On systems that provide @file{libgfortran} as a shared and a static | |
1030 | library, this option forces the use of the static version. If no | |
1031 | shared version of @file{libgfortran} was built when the compiler was | |
1032 | configured, this option has no effect. | |
1033 | @end table | |
1034 | ||
1035 | ||
eaa90d25 | 1036 | @node Runtime Options |
a2bef74c | 1037 | @section Influencing runtime behavior |
e739dfac | 1038 | @cindex options, runtime |
eaa90d25 | 1039 | |
7fc15ba5 | 1040 | These options affect the runtime behavior of programs compiled with GNU Fortran. |
4d04d67a | 1041 | |
eaa90d25 | 1042 | @table @gcctabopt |
eaa90d25 | 1043 | @item -fconvert=@var{conversion} |
32864778 | 1044 | @opindex @code{fconvert=}@var{conversion} |
eaa90d25 TK |
1045 | Specify the representation of data for unformatted files. Valid |
1046 | values for conversion are: @samp{native}, the default; @samp{swap}, | |
1047 | swap between big- and little-endian; @samp{big-endian}, use big-endian | |
1048 | representation for unformatted files; @samp{little-endian}, use little-endian | |
1049 | representation for unformatted files. | |
1050 | ||
1051 | @emph{This option has an effect only when used in the main program. | |
1052 | The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment | |
40746dcc | 1053 | variable override the default specified by @option{-fconvert}.} |
d67ab5ee | 1054 | |
082b0571 JD |
1055 | |
1056 | @item -fno-range-check | |
c3280643 | 1057 | @opindex @code{fno-range-check} |
082b0571 JD |
1058 | Disable range checking of input values during integer @code{READ} operations. |
1059 | For example, GNU Fortran will give an error if an input value is | |
1060 | outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}]. In other words, | |
1061 | with @code{INTEGER (kind=4) :: i} , attempting to read @math{-2147483648} will | |
1062 | give an error unless @option{-fno-range-check} is given. | |
1063 | ||
1064 | ||
d67ab5ee | 1065 | @item -frecord-marker=@var{length} |
32864778 | 1066 | @opindex @code{frecord-marker=}@var{length} |
d67ab5ee | 1067 | Specify the length of record markers for unformatted files. |
07b3bbf2 | 1068 | Valid values for @var{length} are 4 and 8. Default is 4. |
a2bef74c | 1069 | @emph{This is different from previous versions of @command{gfortran}}, |
07b3bbf2 TK |
1070 | which specified a default record marker length of 8 on most |
1071 | systems. If you want to read or write files compatible | |
a2bef74c | 1072 | with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}. |
07b3bbf2 | 1073 | |
07b3bbf2 | 1074 | @item -fmax-subrecord-length=@var{length} |
32864778 | 1075 | @opindex @code{fmax-subrecord-length=}@var{length} |
07b3bbf2 TK |
1076 | Specify the maximum length for a subrecord. The maximum permitted |
1077 | value for length is 2147483639, which is also the default. Only | |
1078 | really useful for use by the gfortran testsuite. | |
0483c79f JD |
1079 | |
1080 | @item -fsign-zero | |
1081 | @opindex @code{fsign-zero} | |
60d340ef TB |
1082 | When enabled, floating point numbers of value zero with the sign bit set |
1083 | are written as negative number in formatted output and treated as | |
1084 | negative in the @code{SIGN} intrinsic. @code{fno-sign-zero} does not | |
1085 | print the negative sign of zero values and regards zero as positive | |
1086 | number in the @code{SIGN} intrinsic for compatibility with F77. | |
1087 | Default behavior is to show the negative sign. | |
eaa90d25 TK |
1088 | @end table |
1089 | ||
6de9cd9a | 1090 | @node Code Gen Options |
a2bef74c | 1091 | @section Options for code generation conventions |
6de9cd9a DN |
1092 | @cindex code generation, conventions |
1093 | @cindex options, code generation | |
e739dfac | 1094 | @cindex options, run-time |
6de9cd9a DN |
1095 | |
1096 | These machine-independent options control the interface conventions | |
1097 | used in code generation. | |
1098 | ||
1099 | Most of them have both positive and negative forms; the negative form | |
1100 | of @option{-ffoo} would be @option{-fno-foo}. In the table below, only | |
1101 | one of the forms is listed---the one which is not the default. You | |
1102 | can figure out the other form by either removing @option{no-} or adding | |
1103 | it. | |
1104 | ||
6de9cd9a | 1105 | @table @gcctabopt |
ee5426a4 | 1106 | @item -fno-automatic |
32864778 | 1107 | @opindex @code{fno-automatic} |
e739dfac DF |
1108 | @cindex @code{SAVE} statement |
1109 | @cindex statement, @code{SAVE} | |
1e7de83b AL |
1110 | Treat each program unit (except those marked as RECURSIVE) as if the |
1111 | @code{SAVE} statement were specified for every local variable and array | |
1112 | referenced in it. Does not affect common blocks. (Some Fortran compilers | |
1113 | provide this option under the name @option{-static} or @option{-save}.) | |
1114 | The default, which is @option{-fautomatic}, uses the stack for local | |
1115 | variables smaller than the value given by @option{-fmax-stack-var-size}. | |
1116 | Use the option @option{-frecursive} to use no static memory. | |
ee5426a4 | 1117 | |
973ff4c0 | 1118 | @item -ff2c |
e739dfac | 1119 | @opindex ff2c |
973ff4c0 TS |
1120 | @cindex calling convention |
1121 | @cindex @command{f2c} calling convention | |
1122 | @cindex @command{g77} calling convention | |
1123 | @cindex libf2c calling convention | |
1124 | Generate code designed to be compatible with code generated | |
1125 | by @command{g77} and @command{f2c}. | |
1126 | ||
1127 | The calling conventions used by @command{g77} (originally implemented | |
1128 | in @command{f2c}) require functions that return type | |
1129 | default @code{REAL} to actually return the C type @code{double}, and | |
1130 | functions that return type @code{COMPLEX} to return the values via an | |
1131 | extra argument in the calling sequence that points to where to | |
1132 | store the return value. Under the default GNU calling conventions, such | |
1133 | functions simply return their results as they would in GNU | |
8556236b | 1134 | C---default @code{REAL} functions return the C type @code{float}, and |
973ff4c0 | 1135 | @code{COMPLEX} functions return the GNU C type @code{complex}. |
a226fc2b TS |
1136 | Additionally, this option implies the @option{-fsecond-underscore} |
1137 | option, unless @option{-fno-second-underscore} is explicitly requested. | |
973ff4c0 TS |
1138 | |
1139 | This does not affect the generation of code that interfaces with | |
1140 | the @command{libgfortran} library. | |
1141 | ||
40746dcc BM |
1142 | @emph{Caution:} It is not a good idea to mix Fortran code compiled with |
1143 | @option{-ff2c} with code compiled with the default @option{-fno-f2c} | |
973ff4c0 TS |
1144 | calling conventions as, calling @code{COMPLEX} or default @code{REAL} |
1145 | functions between program parts which were compiled with different | |
1146 | calling conventions will break at execution time. | |
1147 | ||
1148 | @emph{Caution:} This will break code which passes intrinsic functions | |
1149 | of type default @code{REAL} or @code{COMPLEX} as actual arguments, as | |
40746dcc | 1150 | the library implementations use the @option{-fno-f2c} calling conventions. |
973ff4c0 | 1151 | |
6de9cd9a | 1152 | @item -fno-underscoring |
32864778 | 1153 | @opindex @code{fno-underscoring} |
6de9cd9a DN |
1154 | @cindex underscore |
1155 | @cindex symbol names, underscores | |
1156 | @cindex transforming symbol names | |
1157 | @cindex symbol names, transforming | |
1158 | Do not transform names of entities specified in the Fortran | |
1159 | source file by appending underscores to them. | |
1160 | ||
7fc15ba5 | 1161 | With @option{-funderscoring} in effect, GNU Fortran appends one |
5724da63 JD |
1162 | underscore to external names with no underscores. This is done to ensure |
1163 | compatibility with code produced by many UNIX Fortran compilers. | |
973ff4c0 | 1164 | |
7fc15ba5 | 1165 | @emph{Caution}: The default behavior of GNU Fortran is |
973ff4c0 | 1166 | incompatible with @command{f2c} and @command{g77}, please use the |
b4cbcd1a | 1167 | @option{-ff2c} option if you want object files compiled with |
7fc15ba5 | 1168 | GNU Fortran to be compatible with object code created with these |
b4cbcd1a | 1169 | tools. |
6de9cd9a DN |
1170 | |
1171 | Use of @option{-fno-underscoring} is not recommended unless you are | |
7fc15ba5 | 1172 | experimenting with issues such as integration of GNU Fortran into |
8307c61b FXC |
1173 | existing system environments (vis-@`{a}-vis existing libraries, tools, |
1174 | and so on). | |
6de9cd9a DN |
1175 | |
1176 | For example, with @option{-funderscoring}, and assuming other defaults like | |
40746dcc BM |
1177 | @option{-fcase-lower} and that @code{j()} and @code{max_count()} are |
1178 | external functions while @code{my_var} and @code{lvar} are local variables, | |
6de9cd9a | 1179 | a statement like |
6de9cd9a DN |
1180 | @smallexample |
1181 | I = J() + MAX_COUNT (MY_VAR, LVAR) | |
1182 | @end smallexample | |
6de9cd9a DN |
1183 | @noindent |
1184 | is implemented as something akin to: | |
6de9cd9a DN |
1185 | @smallexample |
1186 | i = j_() + max_count__(&my_var__, &lvar); | |
1187 | @end smallexample | |
1188 | ||
1189 | With @option{-fno-underscoring}, the same statement is implemented as: | |
1190 | ||
1191 | @smallexample | |
1192 | i = j() + max_count(&my_var, &lvar); | |
1193 | @end smallexample | |
1194 | ||
1195 | Use of @option{-fno-underscoring} allows direct specification of | |
7fc15ba5 | 1196 | user-defined names while debugging and when interfacing GNU Fortran |
6de9cd9a DN |
1197 | code with other languages. |
1198 | ||
1199 | Note that just because the names match does @emph{not} mean that the | |
7fc15ba5 | 1200 | interface implemented by GNU Fortran for an external name matches the |
6de9cd9a | 1201 | interface implemented by some other language for that same name. |
7fc15ba5 | 1202 | That is, getting code produced by GNU Fortran to link to code produced |
6de9cd9a DN |
1203 | by some other compiler using this or any other method can be only a |
1204 | small part of the overall solution---getting the code generated by | |
1205 | both compilers to agree on issues other than naming can require | |
1206 | significant effort, and, unlike naming disagreements, linkers normally | |
1207 | cannot detect disagreements in these other areas. | |
1208 | ||
1209 | Also, note that with @option{-fno-underscoring}, the lack of appended | |
1210 | underscores introduces the very real possibility that a user-defined | |
1211 | external name will conflict with a name in a system library, which | |
1212 | could make finding unresolved-reference bugs quite difficult in some | |
1213 | cases---they might occur at program run time, and show up only as | |
1214 | buggy behavior at run time. | |
1215 | ||
7fc15ba5 | 1216 | In future versions of GNU Fortran we hope to improve naming and linking |
6de9cd9a DN |
1217 | issues so that debugging always involves using the names as they appear |
1218 | in the source, even if the names as seen by the linker are mangled to | |
1219 | prevent accidental linking between procedures with incompatible | |
1220 | interfaces. | |
1221 | ||
71a7778c PT |
1222 | @item -fwhole-file |
1223 | @opindex @code{fwhole-file} | |
1224 | By default, GNU Fortran parses, resolves and translates each procedure | |
1225 | in a file separately. Using this option modifies this such that the | |
1226 | whole file is parsed and placed in a single front-end tree. During | |
1227 | resolution, in addition to all the usual checks and fixups, references | |
1228 | to external procedures that are in the same file effect resolution of | |
1229 | that procedure, if not already done, and a check of the interfaces. The | |
1230 | dependences are resolved by changing the order in which the file is | |
1231 | translated into the backend tree. Thus, a procedure that is referenced | |
1232 | is translated before the reference and the duplication of backend tree | |
1233 | declarations eliminated. | |
1234 | ||
973ff4c0 | 1235 | @item -fsecond-underscore |
32864778 | 1236 | @opindex @code{fsecond-underscore} |
6de9cd9a DN |
1237 | @cindex underscore |
1238 | @cindex symbol names, underscores | |
1239 | @cindex transforming symbol names | |
1240 | @cindex symbol names, transforming | |
973ff4c0 TS |
1241 | @cindex @command{f2c} calling convention |
1242 | @cindex @command{g77} calling convention | |
1243 | @cindex libf2c calling convention | |
7fc15ba5 BM |
1244 | By default, GNU Fortran appends an underscore to external |
1245 | names. If this option is used GNU Fortran appends two | |
973ff4c0 | 1246 | underscores to names with underscores and one underscore to external names |
7fc15ba5 | 1247 | with no underscores. GNU Fortran also appends two underscores to |
973ff4c0 TS |
1248 | internal names with underscores to avoid naming collisions with external |
1249 | names. | |
6de9cd9a DN |
1250 | |
1251 | This option has no effect if @option{-fno-underscoring} is | |
973ff4c0 | 1252 | in effect. It is implied by the @option{-ff2c} option. |
6de9cd9a | 1253 | |
40746dcc | 1254 | Otherwise, with this option, an external name such as @code{MAX_COUNT} |
6de9cd9a | 1255 | is implemented as a reference to the link-time external symbol |
40746dcc | 1256 | @code{max_count__}, instead of @code{max_count_}. This is required |
973ff4c0 TS |
1257 | for compatibility with @command{g77} and @command{f2c}, and is implied |
1258 | by use of the @option{-ff2c} option. | |
6de9cd9a | 1259 | |
f4d1d50a TB |
1260 | @item -fcoarray=@var{<keyword>} |
1261 | @opindex @code{fcoarray} | |
1262 | @cindex coarrays | |
1263 | ||
1264 | @table @asis | |
1265 | @item @samp{none} | |
1266 | Disable coarray support; using coarray declarations and image-control | |
1267 | statements will produce a compile-time error. (Default) | |
1268 | ||
1269 | @item @samp{single} | |
1270 | Single-image mode, i.e. @code{num_images()} is always one. | |
60386f50 TB |
1271 | |
1272 | @item @samp{lib} | |
1273 | Library-based coarray parallelization; a suitable GNU Fortran coarray | |
1274 | library needs to be linked. | |
f4d1d50a TB |
1275 | @end table |
1276 | ||
1277 | ||
d3d3011f FXC |
1278 | @item -fcheck=@var{<keyword>} |
1279 | @opindex @code{fcheck} | |
e739dfac | 1280 | @cindex array, bounds checking |
6de9cd9a | 1281 | @cindex bounds checking |
20460eb9 | 1282 | @cindex pointer checking |
22bdbb0f | 1283 | @cindex memory checking |
6de9cd9a | 1284 | @cindex range checking |
6de9cd9a DN |
1285 | @cindex subscript checking |
1286 | @cindex checking subscripts | |
d3d3011f FXC |
1287 | @cindex run-time checking |
1288 | @cindex checking array temporaries | |
1289 | ||
1290 | Enable the generation of run-time checks; the argument shall be | |
1291 | a comma-delimited list of the following keywords. | |
1292 | ||
1293 | @table @asis | |
1294 | @item @samp{all} | |
1295 | Enable all run-time test of @option{-fcheck}. | |
1296 | ||
1297 | @item @samp{array-temps} | |
1298 | Warns at run time when for passing an actual argument a temporary array | |
1299 | had to be generated. The information generated by this warning is | |
1300 | sometimes useful in optimization, in order to avoid such temporaries. | |
1301 | ||
1302 | Note: The warning is only printed once per location. | |
1303 | ||
1304 | @item @samp{bounds} | |
6de9cd9a DN |
1305 | Enable generation of run-time checks for array subscripts |
1306 | and against the declared minimum and maximum values. It also | |
1307 | checks array indices for assumed and deferred | |
aad9c4f4 AM |
1308 | shape arrays against the actual allocated bounds and ensures that all string |
1309 | lengths are equal for character array constructors without an explicit | |
1310 | typespec. | |
6de9cd9a | 1311 | |
d3d3011f | 1312 | Some checks require that @option{-fcheck=bounds} is set for |
8307c61b | 1313 | the compilation of the main program. |
18fe404f | 1314 | |
aad9c4f4 AM |
1315 | Note: In the future this may also include other forms of checking, e.g., |
1316 | checking substring references. | |
43998ed9 | 1317 | |
33abc845 TB |
1318 | @item @samp{do} |
1319 | Enable generation of run-time checks for invalid modification of loop | |
1320 | iteration variables. | |
1321 | ||
22bdbb0f TB |
1322 | @item @samp{mem} |
1323 | Enable generation of run-time checks for memory allocation. | |
1324 | Note: This option does not affect explicit allocations using the | |
1325 | @code{ALLOCATE} statement, which will be always checked. | |
1326 | ||
20460eb9 TB |
1327 | @item @samp{pointer} |
1328 | Enable generation of run-time checks for pointers and allocatables. | |
1329 | ||
43998ed9 TB |
1330 | @item @samp{recursion} |
1331 | Enable generation of run-time checks for recursively called subroutines and | |
1332 | functions which are not marked as recursive. See also @option{-frecursive}. | |
8b5f6dd8 | 1333 | Note: This check does not work for OpenMP programs and is disabled if used |
5b130807 | 1334 | together with @option{-frecursive} and @option{-fopenmp}. |
d3d3011f | 1335 | @end table |
6de9cd9a | 1336 | |
0d52899f | 1337 | |
d3d3011f FXC |
1338 | @item -fbounds-check |
1339 | @opindex @code{fbounds-check} | |
1340 | @c Note: This option is also referred in gcc's manpage | |
1341 | Deprecated alias for @option{-fcheck=bounds}. | |
0d52899f | 1342 | |
d3d3011f FXC |
1343 | @item -fcheck-array-temporaries |
1344 | @opindex @code{fcheck-array-temporaries} | |
1345 | Deprecated alias for @option{-fcheck=array-temps}. | |
0d52899f | 1346 | |
63346ddb SK |
1347 | @item -fmax-array-constructor=@var{n} |
1348 | @opindex @code{fmax-array-constructor} | |
1349 | This option can be used to increase the upper limit permitted in | |
1350 | array constructors. The code below requires this option to expand | |
1351 | the array at compile time. | |
1352 | ||
1353 | @smallexample | |
ab940b73 RW |
1354 | program test |
1355 | implicit none | |
1356 | integer j | |
1357 | integer, parameter :: n = 100000 | |
1358 | integer, parameter :: i(n) = (/ (2*j, j = 1, n) /) | |
1359 | print '(10(I0,1X))', i | |
1360 | end program test | |
63346ddb SK |
1361 | @end smallexample |
1362 | ||
1363 | @emph{Caution: This option can lead to long compile times and excessively | |
1364 | large object files.} | |
1365 | ||
1366 | The default value for @var{n} is 65535. | |
1367 | ||
1368 | ||
6de9cd9a | 1369 | @item -fmax-stack-var-size=@var{n} |
32864778 | 1370 | @opindex @code{fmax-stack-var-size} |
6de9cd9a | 1371 | This option specifies the size in bytes of the largest array that will be put |
1e7de83b AL |
1372 | on the stack; if the size is exceeded static memory is used (except in |
1373 | procedures marked as RECURSIVE). Use the option @option{-frecursive} to | |
1374 | allow for recursive procedures which do not have a RECURSIVE attribute or | |
1375 | for parallel programs. Use @option{-fno-automatic} to never use the stack. | |
6de9cd9a DN |
1376 | |
1377 | This option currently only affects local arrays declared with constant | |
1378 | bounds, and may not apply to all character variables. | |
7fc15ba5 | 1379 | Future versions of GNU Fortran may improve this behavior. |
6de9cd9a DN |
1380 | |
1381 | The default value for @var{n} is 32768. | |
1382 | ||
c76f8d52 MM |
1383 | @item -fstack-arrays |
1384 | @opindex @code{fstack-arrays} | |
1385 | Adding this option will make the fortran compiler put all local arrays, | |
1386 | even those of unknown size onto stack memory. If your program uses very | |
1387 | large local arrays it's possible that you'll have to extend your runtime | |
1388 | limits for stack memory on some operating systems. | |
1389 | ||
5139e1e9 | 1390 | @item -fpack-derived |
32864778 DF |
1391 | @opindex @code{fpack-derived} |
1392 | @cindex structure packing | |
7fc15ba5 | 1393 | This option tells GNU Fortran to pack derived type members as closely as |
2d8b59df | 1394 | possible. Code compiled with this option is likely to be incompatible |
6de9cd9a DN |
1395 | with code compiled without this option, and may execute slower. |
1396 | ||
6de9cd9a | 1397 | @item -frepack-arrays |
32864778 DF |
1398 | @opindex @code{frepack-arrays} |
1399 | @cindex repacking arrays | |
7fc15ba5 | 1400 | In some circumstances GNU Fortran may pass assumed shape array |
02712c16 | 1401 | sections via a descriptor describing a noncontiguous area of memory. |
6de9cd9a DN |
1402 | This option adds code to the function prologue to repack the data into |
1403 | a contiguous block at runtime. | |
1404 | ||
1405 | This should result in faster accesses to the array. However it can introduce | |
1406 | significant overhead to the function call, especially when the passed data | |
02712c16 | 1407 | is noncontiguous. |
a63dad5b | 1408 | |
a63dad5b | 1409 | @item -fshort-enums |
32864778 | 1410 | @opindex @code{fshort-enums} |
a63dad5b | 1411 | This option is provided for interoperability with C code that was |
4ba96c02 | 1412 | compiled with the @option{-fshort-enums} option. It will make |
7fc15ba5 | 1413 | GNU Fortran choose the smallest @code{INTEGER} kind a given |
a63dad5b | 1414 | enumerator set will fit in, and give all its enumerators this kind. |
5a0aad31 | 1415 | |
5a0aad31 | 1416 | @item -fexternal-blas |
32864778 | 1417 | @opindex @code{fexternal-blas} |
a2bef74c DF |
1418 | This option will make @command{gfortran} generate calls to BLAS functions |
1419 | for some matrix operations like @code{MATMUL}, instead of using our own | |
5a0aad31 | 1420 | algorithms, if the size of the matrices involved is larger than a given |
4ba96c02 | 1421 | limit (see @option{-fblas-matmul-limit}). This may be profitable if an |
5a0aad31 FXC |
1422 | optimized vendor BLAS library is available. The BLAS library will have |
1423 | to be specified at link time. | |
1424 | ||
5a0aad31 | 1425 | @item -fblas-matmul-limit=@var{n} |
32864778 | 1426 | @opindex @code{fblas-matmul-limit} |
4ba96c02 | 1427 | Only significant when @option{-fexternal-blas} is in effect. |
5a0aad31 FXC |
1428 | Matrix multiplication of matrices with size larger than (or equal to) @var{n} |
1429 | will be performed by calls to BLAS functions, while others will be | |
1430 | handled by @command{gfortran} internal algorithms. If the matrices | |
1431 | involved are not square, the size comparison is performed using the | |
1432 | geometric mean of the dimensions of the argument and result matrices. | |
1433 | ||
1434 | The default value for @var{n} is 30. | |
1435 | ||
1e7de83b AL |
1436 | @item -frecursive |
1437 | @opindex @code{frecursive} | |
1438 | Allow indirect recursion by forcing all local arrays to be allocated | |
1439 | on the stack. This flag cannot be used together with | |
1440 | @option{-fmax-stack-var-size=} or @option{-fno-automatic}. | |
1441 | ||
51b09ce3 | 1442 | @item -finit-local-zero |
4d04d67a RW |
1443 | @itemx -finit-integer=@var{n} |
1444 | @itemx -finit-real=@var{<zero|inf|-inf|nan|snan>} | |
1445 | @itemx -finit-logical=@var{<true|false>} | |
1446 | @itemx -finit-character=@var{n} | |
51b09ce3 AL |
1447 | @opindex @code{finit-local-zero} |
1448 | @opindex @code{finit-integer} | |
1449 | @opindex @code{finit-real} | |
1450 | @opindex @code{finit-logical} | |
1451 | @opindex @code{finit-character} | |
1452 | The @option{-finit-local-zero} option instructs the compiler to | |
1453 | initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX} | |
1454 | variables to zero, @code{LOGICAL} variables to false, and | |
1455 | @code{CHARACTER} variables to a string of null bytes. Finer-grained | |
1456 | initialization options are provided by the | |
1457 | @option{-finit-integer=@var{n}}, | |
346a77d1 | 1458 | @option{-finit-real=@var{<zero|inf|-inf|nan|snan>}} (which also initializes |
51b09ce3 AL |
1459 | the real and imaginary parts of local @code{COMPLEX} variables), |
1460 | @option{-finit-logical=@var{<true|false>}}, and | |
1461 | @option{-finit-character=@var{n}} (where @var{n} is an ASCII character | |
1462 | value) options. These options do not initialize components of derived | |
1463 | type variables, nor do they initialize variables that appear in an | |
1464 | @code{EQUIVALENCE} statement. (This limitation may be removed in | |
1465 | future releases). | |
1466 | ||
1467 | Note that the @option{-finit-real=nan} option initializes @code{REAL} | |
346a77d1 TB |
1468 | and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN |
1469 | use @option{-finit-real=snan}; note, however, that compile-time | |
1470 | optimizations may convert them into quiet NaN and that trapping | |
1471 | needs to be enabled (e.g. via @option{-ffpe-trap}). | |
f613cea7 JW |
1472 | |
1473 | @item -falign-commons | |
1474 | @opindex @code{falign-commons} | |
ab940b73 | 1475 | @cindex alignment of @code{COMMON} blocks |
f613cea7 | 1476 | By default, @command{gfortran} enforces proper alignment of all variables in a |
ab940b73 RW |
1477 | @code{COMMON} block by padding them as needed. On certain platforms this is mandatory, |
1478 | on others it increases performance. If a @code{COMMON} block is not declared with | |
f613cea7 | 1479 | consistent data types everywhere, this padding can cause trouble, and |
ab940b73 RW |
1480 | @option{-fno-align-commons} can be used to disable automatic alignment. The |
1481 | same form of this option should be used for all files that share a @code{COMMON} block. | |
1482 | To avoid potential alignment issues in @code{COMMON} blocks, it is recommended to order | |
4d04d67a | 1483 | objects from largest to smallest. |
72bd130e TB |
1484 | |
1485 | @item -fno-protect-parens | |
1486 | @opindex @code{fno-protect-parens} | |
4d04d67a | 1487 | @cindex re-association of parenthesized expressions |
72bd130e TB |
1488 | By default the parentheses in expression are honored for all optimization |
1489 | levels such that the compiler does not do any re-association. Using | |
ab940b73 RW |
1490 | @option{-fno-protect-parens} allows the compiler to reorder @code{REAL} and |
1491 | @code{COMPLEX} expressions to produce faster code. Note that for the re-association | |
72bd130e | 1492 | optimization @option{-fno-signed-zeros} and @option{-fno-trapping-math} |
7a994646 TB |
1493 | need to be in effect. The parentheses protection is enabled by default, unless |
1494 | @option{-Ofast} is given. | |
597553ab PT |
1495 | |
1496 | @item -frealloc-lhs | |
1497 | @opindex @code{frealloc-lhs} | |
1498 | @cindex Reallocate the LHS in assignments | |
1499 | An allocatable left-hand side of an intrinsic assignment is automatically | |
1500 | (re)allocated if it is either unallocated or has a different shape. The | |
1501 | option is enabled by default except when @option{-std=f95} is given. | |
2757d5ec TK |
1502 | |
1503 | @item -faggressive-function-elimination | |
1504 | @opindex @code{faggressive-function-elimination} | |
1505 | @cindex Elimination of functions with identical argument lists | |
1506 | Functions with identical argument lists are eliminated within | |
1507 | statements, regardless of whether these functions are marked | |
1508 | @code{PURE} or not. For example, in | |
1509 | @smallexample | |
1510 | a = f(b,c) + f(b,c) | |
1511 | @end smallexample | |
51a30b32 TK |
1512 | there will only be a single call to @code{f}. This option only works |
1513 | if @option{-ffrontend-optimize} is in effect. | |
1514 | ||
1515 | @item -ffrontend-optimize | |
1516 | @opindex @code{frontend-optimize} | |
1517 | @cindex Front-end optimization | |
1518 | This option performs front-end optimization, based on manipulating | |
1519 | parts the Fortran parse tree. Enabled by default by any @option{-O} | |
1520 | option. Optimizations enabled by this option include elimination of | |
1521 | identical function calls within expressions, removing unnecessary | |
1522 | calls to @code{TRIM} in comparisons and assignments and replacing | |
1523 | @code{TRIM(a)} with @code{a(1:LEN_TRIM(a))}. | |
1524 | It can be deselected by specifying @option{-fno-frontend-optimize}. | |
6de9cd9a DN |
1525 | @end table |
1526 | ||
1527 | @xref{Code Gen Options,,Options for Code Generation Conventions, | |
1528 | gcc,Using the GNU Compiler Collection (GCC)}, for information on more options | |
1529 | offered by the GBE | |
7fc15ba5 | 1530 | shared by @command{gfortran}, @command{gcc}, and other GNU compilers. |
6de9cd9a | 1531 | |
6de9cd9a DN |
1532 | @c man end |
1533 | ||
1534 | @node Environment Variables | |
a2bef74c | 1535 | @section Environment variables affecting @command{gfortran} |
e739dfac | 1536 | @cindex environment variable |
6de9cd9a DN |
1537 | |
1538 | @c man begin ENVIRONMENT | |
1539 | ||
7fc15ba5 | 1540 | The @command{gfortran} compiler currently does not make use of any environment |
6de9cd9a DN |
1541 | variables to control its operation above and beyond those |
1542 | that affect the operation of @command{gcc}. | |
1543 | ||
1544 | @xref{Environment Variables,,Environment Variables Affecting GCC, | |
1545 | gcc,Using the GNU Compiler Collection (GCC)}, for information on environment | |
1546 | variables. | |
1547 | ||
eaa90d25 | 1548 | @xref{Runtime}, for environment variables that affect the |
7fc15ba5 | 1549 | run-time behavior of programs compiled with GNU Fortran. |
6de9cd9a | 1550 | @c man end |