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<h5 class="subsubsection">3.2.2.1 Basic Memory Allocation</h5>

<p><a name="index-allocation-of-memory-with-_0040code_007bmalloc_007d-257"></a>
To allocate a block of memory, call <code>malloc</code>.  The prototype for
this function is in <samp><span class="file">stdlib.h</span></samp>. 
<a name="index-stdlib_002eh-258"></a>
<!-- malloc.h stdlib.h -->
<!-- ISO -->

<div class="defun">
&mdash; Function: void * <b>malloc</b> (<var>size_t size</var>)<var><a name="index-malloc-259"></a></var><br>
<blockquote><p>This function returns a pointer to a newly allocated block <var>size</var>
bytes long, or a null pointer if the block could not be allocated. 
</p></blockquote></div>

   <p>The contents of the block are undefined; you must initialize it yourself
(or use <code>calloc</code> instead; see <a href="Allocating-Cleared-Space.html#Allocating-Cleared-Space">Allocating Cleared Space</a>). 
Normally you would cast the value as a pointer to the kind of object
that you want to store in the block.  Here we show an example of doing
so, and of initializing the space with zeros using the library function
<code>memset</code> (see <a href="Copying-and-Concatenation.html#Copying-and-Concatenation">Copying and Concatenation</a>):

<pre class="smallexample">     struct foo *ptr;
     ...
     ptr = (struct foo *) malloc (sizeof (struct foo));
     if (ptr == 0) abort ();
     memset (ptr, 0, sizeof (struct foo));
</pre>
   <p>You can store the result of <code>malloc</code> into any pointer variable
without a cast, because ISO&nbsp;C<!-- /@w --> automatically converts the type
<code>void *</code> to another type of pointer when necessary.  But the cast
is necessary in contexts other than assignment operators or if you might
want your code to run in traditional C.

   <p>Remember that when allocating space for a string, the argument to
<code>malloc</code> must be one plus the length of the string.  This is
because a string is terminated with a null character that doesn't count
in the &ldquo;length&rdquo; of the string but does need space.  For example:

<pre class="smallexample">     char *ptr;
     ...
     ptr = (char *) malloc (length + 1);
</pre>
   <p class="noindent">See <a href="Representation-of-Strings.html#Representation-of-Strings">Representation of Strings</a>, for more information about this.

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