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<a name="FreeBSD-1"></a>
<h4 class="subsection">21.1.7 FreeBSD</h4>
<a name="index-FreeBSD"></a>

<p>When the ABI of a system call is changed in the FreeBSD kernel, this
is implemented by leaving a compatibility system call using the old
ABI at the existing number and allocating a new system call number for
the version using the new ABI.  As a convenience, when a system call
is caught by name (see <a href="Set-Catchpoints.html#catch-syscall">catch syscall</a>), compatibility system calls
are also caught.
</p>
<p>For example, FreeBSD 12 introduced a new variant of the <code>kevent</code>
system call and catching the <code>kevent</code> system call by name catches
both variants:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) catch syscall kevent
Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
(gdb)
</pre></div>


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