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<h2 class="chapter">2 Import and Export</h2>
<p>When <samp><span class="command">gccgo</span></samp> compiles a package which exports anything, the
export information will be stored directly in the object file. When a
package is imported, <samp><span class="command">gccgo</span></samp> must be able to find the file.
<p><a name="index-g_t_0040file_007b_002egox_007d-7"></a>When Go code imports the package <samp><var>gopackage</var></samp>, <samp><span class="command">gccgo</span></samp>
will look for the import data using the following filenames, using the
first one that it finds.
<dl>
<dt><samp><var>gopackage</var><span class="file">.gox</span></samp><br><dt><samp><span class="file">lib</span><var>gopackage</var><span class="file">.so</span></samp><br><dt><samp><span class="file">lib</span><var>gopackage</var><span class="file">.a</span></samp><br><dt><samp><var>gopackage</var><span class="file">.o</span></samp><dd></dl>
<p>The compiler will search for these files in the directories named by
any <samp><span class="option">-I</span></samp> options, in order in which the directories appear on
the command line. The compiler will then search several standard
system directories. Finally the compiler will search the current
directory (to search the current directory earlier, use ‘<samp><span class="samp">-I.</span></samp>’).
<p>The compiler will extract the export information directly from the
compiled object file. The file <samp><var>gopackage</var><span class="file">.gox</span></samp> will
typically contain nothing but export data. This can be generated from
<samp><var>gopackage</var><span class="file">.o</span></samp> via
<pre class="smallexample"> objcopy -j .go_export <var>gopackage</var>.o <var>gopackage</var>.gox
</pre>
<p>For example, it may be desirable to extract the export information
from several different packages into their independent
<samp><var>gopackage</var><span class="file">.gox</span></samp> files, and then to combine the different
package object files together into a single shared library or archive.
<p>At link time you must explicitly tell <samp><span class="command">gccgo</span></samp> which files to
link together into the executable, as is usual with <samp><span class="command">gcc</span></samp>.
This is different from the behaviour of other Go compilers.
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