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<title>Miscellaneous routines (GNU Compiler Collection (GCC) Internals)</title>

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<a name="Miscellaneous-routines"></a>
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<a name="Miscellaneous-runtime-library-routines"></a>
<h3 class="section">4.6 Miscellaneous runtime library routines</h3>

<a name="Cache-control-functions"></a>
<h4 class="subsection">4.6.1 Cache control functions</h4>
<dl>
<dt><a name="index-_005f_005fclear_005fcache"></a>Runtime Function: <em>void</em> <strong>__clear_cache</strong> <em>(char *<var>beg</var>, char *<var>end</var>)</em></dt>
<dd><p>This function clears the instruction cache between <var>beg</var> and <var>end</var>.
</p></dd></dl>

<a name="Split-stack-functions-and-variables"></a>
<h4 class="subsection">4.6.2 Split stack functions and variables</h4>
<dl>
<dt><a name="index-_005f_005fsplitstack_005ffind"></a>Runtime Function: <em>void *</em> <strong>__splitstack_find</strong> <em>(void *<var>segment_arg</var>, void *<var>sp</var>, size_t <var>len</var>, void **<var>next_segment</var>, void **<var>next_sp</var>, void **<var>initial_sp</var>)</em></dt>
<dd><p>When using <samp>-fsplit-stack</samp>, this call may be used to iterate
over the stack segments.  It may be called like this:
</p><div class="smallexample">
<pre class="smallexample">  void *next_segment = NULL;
  void *next_sp = NULL;
  void *initial_sp = NULL;
  void *stack;
  size_t stack_size;
  while ((stack = __splitstack_find (next_segment, next_sp,
                                     &amp;stack_size, &amp;next_segment,
                                     &amp;next_sp, &amp;initial_sp))
         != NULL)
    {
      /* Stack segment starts at stack and is
         stack_size bytes long.  */
    }
</pre></div>

<p>There is no way to iterate over the stack segments of a different
thread.  However, what is permitted is for one thread to call this
with the <var>segment_arg</var> and <var>sp</var> arguments NULL, to pass
<var>next_segment</var>, <var>next_sp</var>, and <var>initial_sp</var> to a different
thread, and then to suspend one way or another.  A different thread
may run the subsequent <code>__splitstack_find</code> iterations.  Of
course, this will only work if the first thread is suspended while the
second thread is calling <code>__splitstack_find</code>.  If not, the second
thread could be looking at the stack while it is changing, and
anything could happen.
</p></dd></dl>

<dl>
<dt><a name="index-_005f_005fmorestack_005fsegments"></a>Variable: <strong>__morestack_segments</strong></dt>
<dt><a name="index-_005f_005fmorestack_005fcurrent_005fsegment"></a>Variable: <strong>__morestack_current_segment</strong></dt>
<dt><a name="index-_005f_005fmorestack_005finitial_005fsp"></a>Variable: <strong>__morestack_initial_sp</strong></dt>
<dd><p>Internal variables used by the <samp>-fsplit-stack</samp> implementation.
</p></dd></dl>


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