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<a name="mallinfo"></a>
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<a name="mallinfo_002c-malloc_005fstats_002c-mallopt_002d_002d_002dmalloc-support"></a>
<h3 class="section">2.25 <code>mallinfo</code>, <code>malloc_stats</code>, <code>mallopt</code>&mdash;malloc support</h3>
<a name="index-mallinfo"></a>
<a name="index-malloc_005fstats"></a>
<a name="index-mallopt"></a>
<a name="index-_005fmallinfo_005fr"></a>
<a name="index-_005fmalloc_005fstats_005fr"></a>
<a name="index-_005fmallopt_005fr"></a>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;malloc.h&gt;
struct mallinfo mallinfo(void);
void malloc_stats(void);
int mallopt(int <var>parameter</var>, <var>value</var>);

struct mallinfo _mallinfo_r(void *<var>reent</var>);
void _malloc_stats_r(void *<var>reent</var>);
int _mallopt_r(void *<var>reent</var>, int <var>parameter</var>, <var>value</var>);

</pre></div>
<p><strong>Description</strong><br>
<code>mallinfo</code> returns a structure describing the current state of
memory allocation.  The structure is defined in malloc.h.  The
following fields are defined: <code>arena</code> is the total amount of space
in the heap; <code>ordblks</code> is the number of chunks which are not in use;
<code>uordblks</code> is the total amount of space allocated by <code>malloc</code>;
<code>fordblks</code> is the total amount of space not in use; <code>keepcost</code> is
the size of the top most memory block.
</p>
<p><code>malloc_stats</code> print some statistics about memory allocation on
standard error.
</p>
<p><code>mallopt</code> takes a parameter and a value.  The parameters are defined
in malloc.h, and may be one of the following: <code>M_TRIM_THRESHOLD</code>
sets the maximum amount of unused space in the top most block before
releasing it back to the system in <code>free</code> (the space is released by
calling <code>_sbrk_r</code> with a negative argument); <code>M_TOP_PAD</code> is the
amount of padding to allocate whenever <code>_sbrk_r</code> is called to
allocate more space.
</p>
<p>The alternate functions <code>_mallinfo_r</code>, <code>_malloc_stats_r</code>, and
<code>_mallopt_r</code> are reentrant versions.  The extra argument <var>reent</var>
is a pointer to a reentrancy structure.
</p>
<br>
<p><strong>Returns</strong><br>
<code>mallinfo</code> returns a mallinfo structure.  The structure is defined
in malloc.h.
</p>
<p><code>malloc_stats</code> does not return a result.
</p>
<p><code>mallopt</code> returns zero if the parameter could not be set, or
non-zero if it could be set.
</p>
<br>
<p><strong>Portability</strong><br>
<code>mallinfo</code> and <code>mallopt</code> are provided by SVR4, but <code>mallopt</code>
takes different parameters on different systems.  <code>malloc_stats</code> is
not portable.
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