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<h5 class="subsubsection">24.4.7.2 Atomic Types</h5>

<p>To avoid uncertainty about interrupting access to a variable, you can
use a particular data type for which access is always atomic:
<code>sig_atomic_t</code>.  Reading and writing this data type is guaranteed
to happen in a single instruction, so there's no way for a handler to
run &ldquo;in the middle&rdquo; of an access.

   <p>The type <code>sig_atomic_t</code> is always an integer data type, but which
one it is, and how many bits it contains, may vary from machine to
machine.

<!-- signal.h -->
<!-- ISO -->
<div class="defun">
&mdash; Data Type: <b>sig_atomic_t</b><var><a name="index-sig_005fatomic_005ft-2939"></a></var><br>
<blockquote><p>This is an integer data type.  Objects of this type are always accessed
atomically. 
</p></blockquote></div>

   <p>In practice, you can assume that <code>int</code> is atomic. 
You can also assume that pointer
types are atomic; that is very convenient.  Both of these assumptions
are true on all of the machines that the GNU C library supports and on
all POSIX systems we know of. 
<!-- ??? This might fail on a 386 that uses 64-bit pointers. -->

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