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| <h3 class="section">3.14 Options for Directory Search</h3> |
| |
| <p><a name="index-directory-options-964"></a><a name="index-options_002c-directory-search-965"></a><a name="index-search-path-966"></a> |
| These options specify directories to search for header files, for |
| libraries and for parts of the compiler: |
| |
| <dl> |
| <dt><code>-I</code><var>dir</var><dd><a name="index-I-967"></a>Add the directory <var>dir</var> to the head of the list of directories to be |
| searched for header files. This can be used to override a system header |
| file, substituting your own version, since these directories are |
| searched before the system header file directories. However, you should |
| not use this option to add directories that contain vendor-supplied |
| system header files (use <samp><span class="option">-isystem</span></samp> for that). If you use more than |
| one <samp><span class="option">-I</span></samp> option, the directories are scanned in left-to-right |
| order; the standard system directories come after. |
| |
| <p>If a standard system include directory, or a directory specified with |
| <samp><span class="option">-isystem</span></samp>, is also specified with <samp><span class="option">-I</span></samp>, the <samp><span class="option">-I</span></samp> |
| option will be ignored. The directory will still be searched but as a |
| system directory at its normal position in the system include chain. |
| This is to ensure that GCC's procedure to fix buggy system headers and |
| the ordering for the include_next directive are not inadvertently changed. |
| If you really need to change the search order for system directories, |
| use the <samp><span class="option">-nostdinc</span></samp> and/or <samp><span class="option">-isystem</span></samp> options. |
| |
| <br><dt><code>-iquote</code><var>dir</var><dd><a name="index-iquote-968"></a>Add the directory <var>dir</var> to the head of the list of directories to |
| be searched for header files only for the case of ‘<samp><span class="samp">#include |
| "</span><var>file</var><span class="samp">"</span></samp>’; they are not searched for ‘<samp><span class="samp">#include <</span><var>file</var><span class="samp">></span></samp>’, |
| otherwise just like <samp><span class="option">-I</span></samp>. |
| |
| <br><dt><code>-L</code><var>dir</var><dd><a name="index-L-969"></a>Add directory <var>dir</var> to the list of directories to be searched |
| for <samp><span class="option">-l</span></samp>. |
| |
| <br><dt><code>-B</code><var>prefix</var><dd><a name="index-B-970"></a>This option specifies where to find the executables, libraries, |
| include files, and data files of the compiler itself. |
| |
| <p>The compiler driver program runs one or more of the subprograms |
| <samp><span class="file">cpp</span></samp>, <samp><span class="file">cc1</span></samp>, <samp><span class="file">as</span></samp> and <samp><span class="file">ld</span></samp>. It tries |
| <var>prefix</var> as a prefix for each program it tries to run, both with and |
| without ‘<samp><var>machine</var><span class="samp">/</span><var>version</var><span class="samp">/</span></samp>’ (see <a href="Target-Options.html#Target-Options">Target Options</a>). |
| |
| <p>For each subprogram to be run, the compiler driver first tries the |
| <samp><span class="option">-B</span></samp> prefix, if any. If that name is not found, or if <samp><span class="option">-B</span></samp> |
| was not specified, the driver tries two standard prefixes, which are |
| <samp><span class="file">/usr/lib/gcc/</span></samp> and <samp><span class="file">/usr/local/lib/gcc/</span></samp>. If neither of |
| those results in a file name that is found, the unmodified program |
| name is searched for using the directories specified in your |
| <samp><span class="env">PATH</span></samp> environment variable. |
| |
| <p>The compiler will check to see if the path provided by the <samp><span class="option">-B</span></samp> |
| refers to a directory, and if necessary it will add a directory |
| separator character at the end of the path. |
| |
| <p><samp><span class="option">-B</span></samp> prefixes that effectively specify directory names also apply |
| to libraries in the linker, because the compiler translates these |
| options into <samp><span class="option">-L</span></samp> options for the linker. They also apply to |
| includes files in the preprocessor, because the compiler translates these |
| options into <samp><span class="option">-isystem</span></samp> options for the preprocessor. In this case, |
| the compiler appends ‘<samp><span class="samp">include</span></samp>’ to the prefix. |
| |
| <p>The run-time support file <samp><span class="file">libgcc.a</span></samp> can also be searched for using |
| the <samp><span class="option">-B</span></samp> prefix, if needed. If it is not found there, the two |
| standard prefixes above are tried, and that is all. The file is left |
| out of the link if it is not found by those means. |
| |
| <p>Another way to specify a prefix much like the <samp><span class="option">-B</span></samp> prefix is to use |
| the environment variable <samp><span class="env">GCC_EXEC_PREFIX</span></samp>. See <a href="Environment-Variables.html#Environment-Variables">Environment Variables</a>. |
| |
| <p>As a special kludge, if the path provided by <samp><span class="option">-B</span></samp> is |
| <samp><span class="file">[dir/]stage</span><var>N</var><span class="file">/</span></samp>, where <var>N</var> is a number in the range 0 to |
| 9, then it will be replaced by <samp><span class="file">[dir/]include</span></samp>. This is to help |
| with boot-strapping the compiler. |
| |
| <br><dt><code>-specs=</code><var>file</var><dd><a name="index-specs-971"></a>Process <var>file</var> after the compiler reads in the standard <samp><span class="file">specs</span></samp> |
| file, in order to override the defaults that the <samp><span class="file">gcc</span></samp> driver |
| program uses when determining what switches to pass to <samp><span class="file">cc1</span></samp>, |
| <samp><span class="file">cc1plus</span></samp>, <samp><span class="file">as</span></samp>, <samp><span class="file">ld</span></samp>, etc. More than one |
| <samp><span class="option">-specs=</span><var>file</var></samp> can be specified on the command line, and they |
| are processed in order, from left to right. |
| |
| <br><dt><code>--sysroot=</code><var>dir</var><dd><a name="index-sysroot-972"></a>Use <var>dir</var> as the logical root directory for headers and libraries. |
| For example, if the compiler would normally search for headers in |
| <samp><span class="file">/usr/include</span></samp> and libraries in <samp><span class="file">/usr/lib</span></samp>, it will instead |
| search <samp><var>dir</var><span class="file">/usr/include</span></samp> and <samp><var>dir</var><span class="file">/usr/lib</span></samp>. |
| |
| <p>If you use both this option and the <samp><span class="option">-isysroot</span></samp> option, then |
| the <samp><span class="option">--sysroot</span></samp> option will apply to libraries, but the |
| <samp><span class="option">-isysroot</span></samp> option will apply to header files. |
| |
| <p>The GNU linker (beginning with version 2.16) has the necessary support |
| for this option. If your linker does not support this option, the |
| header file aspect of <samp><span class="option">--sysroot</span></samp> will still work, but the |
| library aspect will not. |
| |
| <br><dt><code>-I-</code><dd><a name="index-I_002d-973"></a>This option has been deprecated. Please use <samp><span class="option">-iquote</span></samp> instead for |
| <samp><span class="option">-I</span></samp> directories before the <samp><span class="option">-I-</span></samp> and remove the <samp><span class="option">-I-</span></samp>. |
| Any directories you specify with <samp><span class="option">-I</span></samp> options before the <samp><span class="option">-I-</span></samp> |
| option are searched only for the case of ‘<samp><span class="samp">#include "</span><var>file</var><span class="samp">"</span></samp>’; |
| they are not searched for ‘<samp><span class="samp">#include <</span><var>file</var><span class="samp">></span></samp>’. |
| |
| <p>If additional directories are specified with <samp><span class="option">-I</span></samp> options after |
| the <samp><span class="option">-I-</span></samp>, these directories are searched for all ‘<samp><span class="samp">#include</span></samp>’ |
| directives. (Ordinarily <em>all</em> <samp><span class="option">-I</span></samp> directories are used |
| this way.) |
| |
| <p>In addition, the <samp><span class="option">-I-</span></samp> option inhibits the use of the current |
| directory (where the current input file came from) as the first search |
| directory for ‘<samp><span class="samp">#include "</span><var>file</var><span class="samp">"</span></samp>’. There is no way to |
| override this effect of <samp><span class="option">-I-</span></samp>. With <samp><span class="option">-I.</span></samp> you can specify |
| searching the directory which was current when the compiler was |
| invoked. That is not exactly the same as what the preprocessor does |
| by default, but it is often satisfactory. |
| |
| <p><samp><span class="option">-I-</span></samp> does not inhibit the use of the standard system directories |
| for header files. Thus, <samp><span class="option">-I-</span></samp> and <samp><span class="option">-nostdinc</span></samp> are |
| independent. |
| </dl> |
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