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    <title>clSetMemObjectDestructorCallback</title>
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    <div class="refentry">
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        <a xmlns="http://www.w3.org/1999/xhtml" id="clSetCommandQueueProperty"></a>
        <h1>clSetMemObjectDestructorCallback</h1>
        <p>
            Registers a user callback function with a memory object.
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"><a class="link" href="scalarDataTypes.html" target="pagedisplay">cl_int</a>
                    <strong class="fsfunc">clSetMemObjectDestructorCallback</strong>
                (</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="pagedisplay">cl_mem</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">memobj</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> (CL_CALLBACK  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*pfn_notify</var>)
                        (<a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="pagedisplay">cl_mem</a> memobj, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*user_data</var>), </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*user_data</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <code class="varname">memobj</code>
              </span>
            </dt>
            <dd>
              <p>A valid memory object.</p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">pfn_notify</code>
              </span>
            </dt>
            <dd>
              <p>
                    The callback function that can be registered by the application. This
                    callback function may be called asynchronously by the OpenCL implementation.
                    It is the application's responsibility to ensure that the callback function
                    is thread-safe. The parameters to this callback function are:
                </p>
              <div class="itemizedlist">
                <ul class="itemizedlist" style="list-style-type: disc; ">
                  <li class="listitem" style="list-style-type: disc"><code class="varname">memobj</code>: the memory object being deleted.
                        When the user callback is called by the implementation, this memory object is
                        no longer valid.  <code class="varname">memobj</code> is only provided for reference purposes.
                    </li>
                  <li class="listitem" style="list-style-type: disc"><code class="varname">user_data</code>: a pointer to user supplied data.
                    </li>
                </ul>
              </div>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">user_data</code>
              </span>
            </dt>
            <dd>
              <p>
                    Will be passed as the <code class="varname">user_data</code>
                    argument when <code class="varname">pfn_notify</code> is called. <code class="varname">user_data</code> can be NULL.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
          Each call to <code class="function">clSetMemObjectDestructorCallback</code> registers
          the specified user callback function on a callback stack associated with
          <code class="varname">memobj</code>. The registered user callback functions are called in the
          reverse order in which they were registered. The user callback functions are called
          and then the memory object's resources are freed and the memory object is deleted. This
          provides a mechanism for the application (and libraries) using <code class="varname">memobj</code>
          to be notified when the memory referenced by <code class="varname">host_ptr</code>, specified
          when the memory object is created and used as the storage bits for the memory object,
          can be reused or freed.
        </p>
        <p>
          When the user callback function is called by the implementation, the contents of
          the memory region pointed to by <code class="varname">host_ptr</code> (if the memory object is
          created with <code class="constant">CL_MEM_USE_HOST_PTR</code>) are undefined. The callback
          function is typically used by the application to either free or reuse the memory
          region pointed to by <code class="varname">host_ptr</code>.
        </p>
        <p>
          The behavior of calling expensive system routines, OpenCL API calls to create contexts
          or command-queues, or blocking OpenCL operations from the following list below,
          in a callback is undefined.
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clFinish.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clFinish</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clWaitForEvents.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clWaitForEvents</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to
                    <a class="citerefentry" href="clEnqueueReadBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBuffer</span></span></a>,
                    <a class="citerefentry" href="clEnqueueReadBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBufferRect</span></span></a>,
                    <a class="citerefentry" href="clEnqueueWriteBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBuffer</span></span></a>,
                    <a class="citerefentry" href="clEnqueueWriteBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBufferRect</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to
                        <a class="citerefentry" href="clEnqueueReadImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadImage</span></span></a> and
                        <a class="citerefentry" href="clEnqueueWriteImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to
                        <a class="citerefentry" href="clEnqueueMapBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapBuffer</span></span></a> and
                        <a class="citerefentry" href="clEnqueueMapImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to
                        <a class="citerefentry" href="clBuildProgram.html"><span class="citerefentry"><span class="refentrytitle">clBuildProgram</span></span></a>,
                        <a class="citerefentry" href="clCompileProgram.html"><span class="citerefentry"><span class="refentrytitle">clCompileProgram</span></span></a>, or
                        <a class="citerefentry" href="clLinkProgram.html"><span class="citerefentry"><span class="refentrytitle">clLinkProgram</span></span></a></li>
          </ul>
        </div>
        <p>
          If an application needs to wait for completion of a routine from the above list in a
          callback, please use the non-blocking form of the function, and assign a completion
          callback to it to do the remainder of your work. Note that when a callback (or other
          code) enqueues commands to a command-queue, the commands are not required to begin
          execution until the queue is flushed.  In standard usage, blocking enqueue calls serve
          this role by implicitly flushing the queue. Since blocking calls are not permitted in
          callbacks, those callbacks that enqueue commands on a command queue should either
          call <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a>
          on the queue before returning or arrange for
          <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a> to be called
          later on another thread.
        </p>
        <p>
          The user callback function may not call OpenCL APIs with the memory object for which
          the callback function is invoked and for such cases the behavior of OpenCL APIs is
          considered to be undefined.
        </p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p>
          Returns <span class="errorname">CL_SUCCESS</span> if the function is executed
          successfully. Otherwise, it returns one of the following errors:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_MEM_OBJECT</span> if <code class="varname">memobj</code> is not a valid memory object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if <code class="varname">pfn_notify</code> is NULL.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_RESOURCES</span> if there is a failure to allocate resources required by the
                OpenCL implementation on the device.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_HOST_MEMORY</span> if there is a failure to allocate resources required by the
                OpenCL implementation on the host.
            </li>
          </ul>
        </div>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p><img src="pdficon_small1.gif" />
            <a href="https://www.khronos.org/registry/cl/specs/opencl-2.1.pdf#namedest=clSetMemObjectDestructorCallback" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
            <a class="citerefentry" href="clCreateCommandQueueWithProperties.html"><span class="citerefentry"><span class="refentrytitle">clCreateCommandQueueWithProperties</span></span></a>,
            <a class="citerefentry" href="clGetCommandQueueInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetCommandQueueInfo</span></span></a>,
            <a class="citerefentry" href="clReleaseCommandQueue.html"><span class="citerefentry"><span class="refentrytitle">clReleaseCommandQueue</span></span></a>,
            <a class="citerefentry" href="clRetainCommandQueue.html"><span class="citerefentry"><span class="refentrytitle">clRetainCommandQueue</span></span></a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2015 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
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