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<h4 class="subsection">21.1.7 FreeBSD</h4>

<p><a name="index-FreeBSD-1566"></a>
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="catch-syscall.html#catch-syscall">catch syscall</a>), compatibility system calls
are also caught.

   <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:

<pre class="smallexample">     (gdb) catch syscall kevent
     Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
     (gdb)
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