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<h5 class="subsubsection">3.6.4.2 Input Section Wildcard Patterns</h5>

<p><a name="index-input-section-wildcards-459"></a><a name="index-wildcard-file-name-patterns-460"></a><a name="index-file-name-wildcard-patterns-461"></a><a name="index-section-name-wildcard-patterns-462"></a>In an input section description, either the file name or the section
name or both may be wildcard patterns.

   <p>The file name of &lsquo;<samp><span class="samp">*</span></samp>&rsquo; seen in many examples is a simple wildcard
pattern for the file name.

   <p>The wildcard patterns are like those used by the Unix shell.

     <dl>
<dt>&lsquo;<samp><span class="samp">*</span></samp>&rsquo;<dd>matches any number of characters
<br><dt>&lsquo;<samp><span class="samp">?</span></samp>&rsquo;<dd>matches any single character
<br><dt>&lsquo;<samp><span class="samp">[</span><var>chars</var><span class="samp">]</span></samp>&rsquo;<dd>matches a single instance of any of the <var>chars</var>; the &lsquo;<samp><span class="samp">-</span></samp>&rsquo;
character may be used to specify a range of characters, as in
&lsquo;<samp><span class="samp">[a-z]</span></samp>&rsquo; to match any lower case letter
<br><dt>&lsquo;<samp><span class="samp">\</span></samp>&rsquo;<dd>quotes the following character
</dl>

   <p>When a file name is matched with a wildcard, the wildcard characters
will not match a &lsquo;<samp><span class="samp">/</span></samp>&rsquo; character (used to separate directory names on
Unix).  A pattern consisting of a single &lsquo;<samp><span class="samp">*</span></samp>&rsquo; character is an
exception; it will always match any file name, whether it contains a
&lsquo;<samp><span class="samp">/</span></samp>&rsquo; or not.  In a section name, the wildcard characters will match
a &lsquo;<samp><span class="samp">/</span></samp>&rsquo; character.

   <p>File name wildcard patterns only match files which are explicitly
specified on the command line or in an <code>INPUT</code> command.  The linker
does not search directories to expand wildcards.

   <p>If a file name matches more than one wildcard pattern, or if a file name
appears explicitly and is also matched by a wildcard pattern, the linker
will use the first match in the linker script.  For example, this
sequence of input section descriptions is probably in error, because the
<samp><span class="file">data.o</span></samp> rule will not be used:
<pre class="smallexample">     .data : { *(.data) }
     .data1 : { data.o(.data) }
</pre>
   <p><a name="index-SORT_005fBY_005fNAME-463"></a>Normally, the linker will place files and sections matched by wildcards
in the order in which they are seen during the link.  You can change
this by using the <code>SORT_BY_NAME</code> keyword, which appears before a wildcard
pattern in parentheses (e.g., <code>SORT_BY_NAME(.text*)</code>).  When the
<code>SORT_BY_NAME</code> keyword is used, the linker will sort the files or sections
into ascending order by name before placing them in the output file.

   <p><a name="index-SORT_005fBY_005fALIGNMENT-464"></a><code>SORT_BY_ALIGNMENT</code> is very similar to <code>SORT_BY_NAME</code>. The
difference is <code>SORT_BY_ALIGNMENT</code> will sort sections into
descending order by alignment before placing them in the output file. 
Larger alignments are placed before smaller alignments in order to
reduce the amount of padding necessary.

   <p><a name="index-SORT_005fBY_005fINIT_005fPRIORITY-465"></a><code>SORT_BY_INIT_PRIORITY</code> is very similar to <code>SORT_BY_NAME</code>. The
difference is <code>SORT_BY_INIT_PRIORITY</code> will sort sections into
ascending order by numerical value of the GCC init_priority attribute
encoded in the section name before placing them in the output file.

   <p><a name="index-SORT-466"></a><code>SORT</code> is an alias for <code>SORT_BY_NAME</code>.

   <p>When there are nested section sorting commands in linker script, there
can be at most 1 level of nesting for section sorting commands.

     <ol type=1 start=1>
<li><code>SORT_BY_NAME</code> (<code>SORT_BY_ALIGNMENT</code> (wildcard section pattern)). 
It will sort the input sections by name first, then by alignment if two
sections have the same name. 
<li><code>SORT_BY_ALIGNMENT</code> (<code>SORT_BY_NAME</code> (wildcard section pattern)). 
It will sort the input sections by alignment first, then by name if two
sections have the same alignment. 
<li><code>SORT_BY_NAME</code> (<code>SORT_BY_NAME</code> (wildcard section pattern)) is
treated the same as <code>SORT_BY_NAME</code> (wildcard section pattern). 
<li><code>SORT_BY_ALIGNMENT</code> (<code>SORT_BY_ALIGNMENT</code> (wildcard section pattern))
is treated the same as <code>SORT_BY_ALIGNMENT</code> (wildcard section pattern). 
<li>All other nested section sorting commands are invalid.
        </ol>

   <p>When both command-line section sorting option and linker script
section sorting command are used, section sorting command always
takes precedence over the command-line option.

   <p>If the section sorting command in linker script isn't nested, the
command-line option will make the section sorting command to be
treated as nested sorting command.

     <ol type=1 start=1>
<li><code>SORT_BY_NAME</code> (wildcard section pattern ) with
<samp><span class="option">--sort-sections alignment</span></samp> is equivalent to
<code>SORT_BY_NAME</code> (<code>SORT_BY_ALIGNMENT</code> (wildcard section pattern)). 
<li><code>SORT_BY_ALIGNMENT</code> (wildcard section pattern) with
<samp><span class="option">--sort-section name</span></samp> is equivalent to
<code>SORT_BY_ALIGNMENT</code> (<code>SORT_BY_NAME</code> (wildcard section pattern)).
        </ol>

   <p>If the section sorting command in linker script is nested, the
command-line option will be ignored.

   <p><a name="index-SORT_005fNONE-467"></a><code>SORT_NONE</code> disables section sorting by ignoring the command-line
section sorting option.

   <p>If you ever get confused about where input sections are going, use the
&lsquo;<samp><span class="samp">-M</span></samp>&rsquo; linker option to generate a map file.  The map file shows
precisely how input sections are mapped to output sections.

   <p>This example shows how wildcard patterns might be used to partition
files.  This linker script directs the linker to place all &lsquo;<samp><span class="samp">.text</span></samp>&rsquo;
sections in &lsquo;<samp><span class="samp">.text</span></samp>&rsquo; and all &lsquo;<samp><span class="samp">.bss</span></samp>&rsquo; sections in &lsquo;<samp><span class="samp">.bss</span></samp>&rsquo;. 
The linker will place the &lsquo;<samp><span class="samp">.data</span></samp>&rsquo; section from all files beginning
with an upper case character in &lsquo;<samp><span class="samp">.DATA</span></samp>&rsquo;; for all other files, the
linker will place the &lsquo;<samp><span class="samp">.data</span></samp>&rsquo; section in &lsquo;<samp><span class="samp">.data</span></samp>&rsquo;.
<pre class="smallexample">     SECTIONS {
       .text : { *(.text) }
       .DATA : { [A-Z]*(.data) }
       .data : { *(.data) }
       .bss : { *(.bss) }
     }
</pre>
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