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<h5 class="subsubsection">3.2.5.4 GNU C Variable-Size Arrays</h5>

<p><a name="index-variable_002dsized-arrays-349"></a>
In GNU C, you can replace most uses of <code>alloca</code> with an array of
variable size.  Here is how <code>open2</code> would look then:

<pre class="smallexample">     int open2 (char *str1, char *str2, int flags, int mode)
     {
       char name[strlen (str1) + strlen (str2) + 1];
       stpcpy (stpcpy (name, str1), str2);
       return open (name, flags, mode);
     }
</pre>
   <p>But <code>alloca</code> is not always equivalent to a variable-sized array, for
several reasons:

     <ul>
<li>A variable size array's space is freed at the end of the scope of the
name of the array.  The space allocated with <code>alloca</code>
remains until the end of the function.

     <li>It is possible to use <code>alloca</code> within a loop, allocating an
additional block on each iteration.  This is impossible with
variable-sized arrays. 
</ul>

   <p><strong>NB:</strong> If you mix use of <code>alloca</code> and variable-sized arrays
within one function, exiting a scope in which a variable-sized array was
declared frees all blocks allocated with <code>alloca</code> during the
execution of that scope.

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