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| <title>The GNU Fortran Compiler: Preprocessing Options</title> |
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| <a name="Preprocessing-Options"></a> |
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| Next: <a href="Error-and-Warning-Options.html#Error-and-Warning-Options" accesskey="n" rel="next">Error and Warning Options</a>, Previous: <a href="Fortran-Dialect-Options.html#Fortran-Dialect-Options" accesskey="p" rel="prev">Fortran Dialect Options</a>, Up: <a href="Invoking-GNU-Fortran.html#Invoking-GNU-Fortran" accesskey="u" rel="up">Invoking GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| <hr> |
| <a name="Enable-and-customize-preprocessing"></a> |
| <h3 class="section">2.3 Enable and customize preprocessing</h3> |
| <a name="index-preprocessor"></a> |
| <a name="index-options_002c-preprocessor"></a> |
| <a name="index-CPP-1"></a> |
| |
| <p>Preprocessor related options. See section |
| <a href="Preprocessing-and-conditional-compilation.html#Preprocessing-and-conditional-compilation">Preprocessing and conditional compilation</a> for more detailed |
| information on preprocessing in <code>gfortran</code>. |
| </p> |
| <dl compact="compact"> |
| <dt><code>-cpp</code></dt> |
| <dt><code>-nocpp</code></dt> |
| <dd><a name="index-cpp"></a> |
| <a name="index-fpp"></a> |
| <a name="index-preprocessor_002c-enable"></a> |
| <a name="index-preprocessor_002c-disable"></a> |
| <p>Enable preprocessing. The preprocessor is automatically invoked if |
| the file extension is <samp>.fpp</samp>, <samp>.FPP</samp>, <samp>.F</samp>, <samp>.FOR</samp>, |
| <samp>.FTN</samp>, <samp>.F90</samp>, <samp>.F95</samp>, <samp>.F03</samp> or <samp>.F08</samp>. Use |
| this option to manually enable preprocessing of any kind of Fortran file. |
| </p> |
| <p>To disable preprocessing of files with any of the above listed extensions, |
| use the negative form: <samp>-nocpp</samp>. |
| </p> |
| <p>The preprocessor is run in traditional mode. Any restrictions of the |
| file-format, especially the limits on line length, apply for |
| preprocessed output as well, so it might be advisable to use the |
| <samp>-ffree-line-length-none</samp> or <samp>-ffixed-line-length-none</samp> |
| options. |
| </p> |
| </dd> |
| <dt><code>-dM</code></dt> |
| <dd><a name="index-dM"></a> |
| <a name="index-preprocessor_002c-debugging"></a> |
| <a name="index-debugging_002c-preprocessor"></a> |
| <p>Instead of the normal output, generate a list of <code>'#define'</code> |
| directives for all the macros defined during the execution of the |
| preprocessor, including predefined macros. This gives you a way |
| of finding out what is predefined in your version of the preprocessor. |
| Assuming you have no file <samp>foo.f90</samp>, the command |
| </p><div class="smallexample"> |
| <pre class="smallexample"> touch foo.f90; gfortran -cpp -E -dM foo.f90 |
| </pre></div> |
| <p>will show all the predefined macros. |
| </p> |
| </dd> |
| <dt><code>-dD</code></dt> |
| <dd><a name="index-dD"></a> |
| <a name="index-preprocessor_002c-debugging-1"></a> |
| <a name="index-debugging_002c-preprocessor-1"></a> |
| <p>Like <samp>-dM</samp> except in two respects: it does not include the |
| predefined macros, and it outputs both the <code>#define</code> directives |
| and the result of preprocessing. Both kinds of output go to the |
| standard output file. |
| </p> |
| </dd> |
| <dt><code>-dN</code></dt> |
| <dd><a name="index-dN"></a> |
| <a name="index-preprocessor_002c-debugging-2"></a> |
| <a name="index-debugging_002c-preprocessor-2"></a> |
| <p>Like <samp>-dD</samp>, but emit only the macro names, not their expansions. |
| </p> |
| </dd> |
| <dt><code>-dU</code></dt> |
| <dd><a name="index-dU"></a> |
| <a name="index-preprocessor_002c-debugging-3"></a> |
| <a name="index-debugging_002c-preprocessor-3"></a> |
| <p>Like <samp>dD</samp> except that only macros that are expanded, or whose |
| definedness is tested in preprocessor directives, are output; the |
| output is delayed until the use or test of the macro; and <code>'#undef'</code> |
| directives are also output for macros tested but undefined at the time. |
| </p> |
| </dd> |
| <dt><code>-dI</code></dt> |
| <dd><a name="index-dI"></a> |
| <a name="index-preprocessor_002c-debugging-4"></a> |
| <a name="index-debugging_002c-preprocessor-4"></a> |
| <p>Output <code>'#include'</code> directives in addition to the result |
| of preprocessing. |
| </p> |
| </dd> |
| <dt><code>-fworking-directory</code></dt> |
| <dd><a name="index-fworking_002ddirectory"></a> |
| <a name="index-preprocessor_002c-working-directory"></a> |
| <p>Enable generation of linemarkers in the preprocessor output that will |
| let the compiler know the current working directory at the time of |
| preprocessing. When this option is enabled, the preprocessor will emit, |
| after the initial linemarker, a second linemarker with the current |
| working directory followed by two slashes. GCC will use this directory, |
| when it is present in the preprocessed input, as the directory emitted |
| as the current working directory in some debugging information formats. |
| This option is implicitly enabled if debugging information is enabled, |
| but this can be inhibited with the negated form |
| <samp>-fno-working-directory</samp>. If the <samp>-P</samp> flag is present |
| in the command line, this option has no effect, since no <code>#line</code> |
| directives are emitted whatsoever. |
| </p> |
| </dd> |
| <dt><code>-idirafter <var>dir</var></code></dt> |
| <dd><a name="index-idirafter-dir"></a> |
| <a name="index-preprocessing_002c-include-path"></a> |
| <p>Search <var>dir</var> for include files, but do it after all directories |
| specified with <samp>-I</samp> and the standard system directories have |
| been exhausted. <var>dir</var> is treated as a system include directory. |
| If dir begins with <code>=</code>, then the <code>=</code> will be replaced by |
| the sysroot prefix; see <samp>--sysroot</samp> and <samp>-isysroot</samp>. |
| </p> |
| </dd> |
| <dt><code>-imultilib <var>dir</var></code></dt> |
| <dd><a name="index-imultilib-dir"></a> |
| <a name="index-preprocessing_002c-include-path-1"></a> |
| <p>Use <var>dir</var> as a subdirectory of the directory containing target-specific |
| C++ headers. |
| </p> |
| </dd> |
| <dt><code>-iprefix <var>prefix</var></code></dt> |
| <dd><a name="index-iprefix-prefix"></a> |
| <a name="index-preprocessing_002c-include-path-2"></a> |
| <p>Specify <var>prefix</var> as the prefix for subsequent <samp>-iwithprefix</samp> |
| options. If the <var>prefix</var> represents a directory, you should include |
| the final <code>'/'</code>. |
| </p> |
| </dd> |
| <dt><code>-isysroot <var>dir</var></code></dt> |
| <dd><a name="index-isysroot-dir"></a> |
| <a name="index-preprocessing_002c-include-path-3"></a> |
| <p>This option is like the <samp>--sysroot</samp> option, but applies only to |
| header files. See the <samp>--sysroot</samp> option for more information. |
| </p> |
| </dd> |
| <dt><code>-iquote <var>dir</var></code></dt> |
| <dd><a name="index-iquote-dir"></a> |
| <a name="index-preprocessing_002c-include-path-4"></a> |
| <p>Search <var>dir</var> only for header files requested with <code>#include "file"</code>; |
| they are not searched for <code>#include <file></code>, before all directories |
| specified by <samp>-I</samp> and before the standard system directories. If |
| <var>dir</var> begins with <code>=</code>, then the <code>=</code> will be replaced by the |
| sysroot prefix; see <samp>--sysroot</samp> and <samp>-isysroot</samp>. |
| </p> |
| </dd> |
| <dt><code>-isystem <var>dir</var></code></dt> |
| <dd><a name="index-isystem-dir"></a> |
| <a name="index-preprocessing_002c-include-path-5"></a> |
| <p>Search <var>dir</var> for header files, after all directories specified by |
| <samp>-I</samp> but before the standard system directories. Mark it as a |
| system directory, so that it gets the same special treatment as is |
| applied to the standard system directories. If <var>dir</var> begins with |
| <code>=</code>, then the <code>=</code> will be replaced by the sysroot prefix; |
| see <samp>--sysroot</samp> and <samp>-isysroot</samp>. |
| </p> |
| </dd> |
| <dt><code>-nostdinc</code></dt> |
| <dd><a name="index-nostdinc"></a> |
| <p>Do not search the standard system directories for header files. Only |
| the directories you have specified with <samp>-I</samp> options (and the |
| directory of the current file, if appropriate) are searched. |
| </p> |
| </dd> |
| <dt><code>-undef</code></dt> |
| <dd><a name="index-undef"></a> |
| <p>Do not predefine any system-specific or GCC-specific macros. |
| The standard predefined macros remain defined. |
| </p> |
| </dd> |
| <dt><code>-A<var>predicate</var>=<var>answer</var></code></dt> |
| <dd><a name="index-Apredicate_003danswer"></a> |
| <a name="index-preprocessing_002c-assertion"></a> |
| <p>Make an assertion with the predicate <var>predicate</var> and answer <var>answer</var>. |
| This form is preferred to the older form -A predicate(answer), which is still |
| supported, because it does not use shell special characters. |
| </p> |
| </dd> |
| <dt><code>-A-<var>predicate</var>=<var>answer</var></code></dt> |
| <dd><a name="index-A_002dpredicate_003danswer"></a> |
| <a name="index-preprocessing_002c-assertion-1"></a> |
| <p>Cancel an assertion with the predicate <var>predicate</var> and answer <var>answer</var>. |
| </p> |
| </dd> |
| <dt><code>-C</code></dt> |
| <dd><a name="index-C"></a> |
| <a name="index-preprocessing_002c-keep-comments"></a> |
| <p>Do not discard comments. All comments are passed through to the output |
| file, except for comments in processed directives, which are deleted |
| along with the directive. |
| </p> |
| <p>You should be prepared for side effects when using <samp>-C</samp>; it causes |
| the preprocessor to treat comments as tokens in their own right. For example, |
| comments appearing at the start of what would be a directive line have the |
| effect of turning that line into an ordinary source line, since the first |
| token on the line is no longer a <code>'#'</code>. |
| </p> |
| <p>Warning: this currently handles C-Style comments only. The preprocessor |
| does not yet recognize Fortran-style comments. |
| </p> |
| </dd> |
| <dt><code>-CC</code></dt> |
| <dd><a name="index-CC"></a> |
| <a name="index-preprocessing_002c-keep-comments-1"></a> |
| <p>Do not discard comments, including during macro expansion. This is like |
| <samp>-C</samp>, except that comments contained within macros are also passed |
| through to the output file where the macro is expanded. |
| </p> |
| <p>In addition to the side-effects of the <samp>-C</samp> option, the <samp>-CC</samp> |
| option causes all C++-style comments inside a macro to be converted to C-style |
| comments. This is to prevent later use of that macro from inadvertently |
| commenting out the remainder of the source line. The <samp>-CC</samp> option |
| is generally used to support lint comments. |
| </p> |
| <p>Warning: this currently handles C- and C++-Style comments only. The |
| preprocessor does not yet recognize Fortran-style comments. |
| </p> |
| </dd> |
| <dt><code>-D<var>name</var></code></dt> |
| <dd><a name="index-Dname"></a> |
| <a name="index-preprocessing_002c-define-macros"></a> |
| <p>Predefine name as a macro, with definition <code>1</code>. |
| </p> |
| </dd> |
| <dt><code>-D<var>name</var>=<var>definition</var></code></dt> |
| <dd><a name="index-Dname_003ddefinition"></a> |
| <a name="index-preprocessing_002c-define-macros-1"></a> |
| <p>The contents of <var>definition</var> are tokenized and processed as if they |
| appeared during translation phase three in a <code>'#define'</code> directive. |
| In particular, the definition will be truncated by embedded newline |
| characters. |
| </p> |
| <p>If you are invoking the preprocessor from a shell or shell-like program |
| you may need to use the shell’s quoting syntax to protect characters such |
| as spaces that have a meaning in the shell syntax. |
| </p> |
| <p>If you wish to define a function-like macro on the command line, write |
| its argument list with surrounding parentheses before the equals sign |
| (if any). Parentheses are meaningful to most shells, so you will need |
| to quote the option. With sh and csh, <code>-D'name(args...)=definition'</code> |
| works. |
| </p> |
| <p><samp>-D</samp> and <samp>-U</samp> options are processed in the order they are |
| given on the command line. All -imacros file and -include file options |
| are processed after all -D and -U options. |
| </p> |
| </dd> |
| <dt><code>-H</code></dt> |
| <dd><a name="index-H"></a> |
| <p>Print the name of each header file used, in addition to other normal |
| activities. Each name is indented to show how deep in the <code>'#include'</code> |
| stack it is. |
| </p> |
| </dd> |
| <dt><code>-P</code></dt> |
| <dd><a name="index-P"></a> |
| <a name="index-preprocessing_002c-no-linemarkers"></a> |
| <p>Inhibit generation of linemarkers in the output from the preprocessor. |
| This might be useful when running the preprocessor on something that |
| is not C code, and will be sent to a program which might be confused |
| by the linemarkers. |
| </p> |
| </dd> |
| <dt><code>-U<var>name</var></code></dt> |
| <dd><a name="index-Uname"></a> |
| <a name="index-preprocessing_002c-undefine-macros"></a> |
| <p>Cancel any previous definition of <var>name</var>, either built in or provided |
| with a <samp>-D</samp> option. |
| </p></dd> |
| </dl> |
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