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<h3 class="section">3.2 Function Names</h3>
<p><a name="index-g_t_0040code_007b_005f_005fasm_005f_005f_007d-10"></a>Go code can call C functions directly using a Go extension implemented
in <samp><span class="command">gccgo</span></samp>: a function declaration may be followed by
<code>__asm__ ("</code><var>name</var><code>")</code>. For example, here is how the C function
<code>open</code> can be declared in Go:
<pre class="smallexample"> func c_open(name *byte, mode int, perm int) int __asm__ ("open");
</pre>
<p>The C function naturally expects a nul terminated string, which in Go
is equivalent to a pointer to an array (not a slice!) of <code>byte</code>
with a terminating zero byte. So a sample call from Go would look
like (after importing the <code>os</code> package):
<pre class="smallexample"> var name = [4]byte{'f', 'o', 'o', 0};
i := c_open(&amp;name[0], os.O_RDONLY, 0);
</pre>
<p>Note that this serves as an example only. To open a file in Go please
use Go's <code>os.Open</code> function instead.
<p>The name of Go functions accessed from C is subject to change. At
present the name of a Go function that does not have a receiver is
<code>prefix.package.Functionname</code>. The prefix is set by the
<samp><span class="option">-fgo-prefix</span></samp> option used when the package is compiled; if the
option is not used, the default is simply <code>go</code>. To call the
function from C you must set the name using the <samp><span class="command">gcc</span></samp>
extension similar to the <samp><span class="command">gccgo</span></samp> extension.
<pre class="smallexample"> extern int go_function(int) __asm__ ("myprefix.mypackage.Function");
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