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<refentry>
    <refentryinfo>
        <keywordset>
            <keyword>clGetExtensionFunctionAddressForPlatform</keyword>
        </keywordset>
    </refentryinfo>

    <refmeta>
        <refentrytitle>clGetExtensionFunctionAddressForPlatform</refentrytitle>

        <refmiscinfo>
            <copyright>
                <year>2007-2011</year>
                <holder>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
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials.</holder>
            </copyright>
        </refmiscinfo>
        <manvolnum>3</manvolnum>
    </refmeta>

<!-- ================================ SYNOPSIS -->

    <refnamediv id="clGetExtensionFunctionAddressForPlatform">
        <refname>clGetExtensionFunctionAddressForPlatform</refname>

        <refpurpose>
            Returns the address of the extension function named by
            <varname>funcname</varname> for a given <varname>platform</varname>.
        </refpurpose>
    </refnamediv>

    <refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>
                   <link xlink:href="scalarDataTypes.html">void*</link>
                    <function>
                        clGetExtensionFunctionAddressForPlatform
                    </function>
                </funcdef>

                <paramdef>
                    <link xlink:href="abstractDataTypes.html">cl_platform_id</link>
                    <parameter>platform</parameter>
                </paramdef>

                <paramdef>const
                    <link xlink:href="scalarDataTypes.html">char</link>
                    <parameter>*funcname</parameter>
               </paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>

<!-- ================================ PARAMETERS -->

    <refsect1 id="parameters">
        <title>Parameters</title>
        <variablelist>
            <varlistentry>
                <term> <varname> funcname </varname> </term>
                <listitem>
                    <para> <!-- parameter description -->
                        Name of an extension function.
                    </para>
               </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>

<!-- ================================ DESCRIPTION  -->

    <refsect1 id="description"><title>Description</title>
        <para>
          The function <function>clGetExtensionFunctionAddressForPlatform</function> returns
          the address of the extension function named by <varname>funcname</varname> for a
          given <varname>platform</varname>. The pointer returned should be cast to a function
          pointer type matching the extension function's definition defined in the appropriate
          extension specification and header file.
        </para>

        <para>
          A return value of NULL indicates that the specified function does not exist for the
          implementation or <varname>platform</varname> is not a valid platform.  A non-NULL
          return value for <function>clGetExtensionFunctionAddressForPlatform</function>
          does not guarantee that an extension function is actually supported by
          the platform. The application must also make a corresponding query using
          <citerefentry><refentrytitle>clGetPlatformInfo</refentrytitle></citerefentry>
          (platform, <constant>CL_PLATFORM_EXTENSIONS</constant>, ... ) or
          <citerefentry><refentrytitle>clGetDeviceInfo</refentrytitle></citerefentry>
          (device,<constant>CL_DEVICE_EXTENSIONS</constant>, ... ) to determine if an extension
          is supported by the OpenCL implementation.
        </para>

        <para>
          <function>clGetExtensionFunctionAddressForPlatform</function> may not be queried
          for core (non-extension) functions in OpenCL. For functions that are queryable with
          <function>clGetExtensionFunctionAddressForPlatform</function>, implementations may
          choose to also export those functions statically from the object libraries implementing
          those functions. However, portable applications cannot rely on this behavior.
        </para>

        <para>
          Function pointer typedefs must be declared for all extensions that add API entrypoints.
          These typedefs are a required part of the extension interface, to be provided in
          an appropriate header (such as <code>cl_ext.h</code> if the extension is an OpenCL
          extension, or <code>cl_gl_ext.h</code> if the extension is an OpenCL/OpenGL sharing
          extension).
        </para>
    </refsect1>

<!-- ================================ NOTES  -->

    <refsect1 id="notes"><title>Notes</title>
        <para>
          Since there is no way to qualify the query with a device, the function pointer
          returned must work for all implementations of that extension on different devices
          for a platform. The behavior of calling a device extension function on a device not
          supporting that extension is undefined.
        </para>
    </refsect1>

<!-- ================================ EXAMPLE  -->
<!-- DO NOT DELETE IN CASE AN EXAMPLE IS ADDED IN THE FUTURE -->

    <refsect2 id="example1">
        <title>
            Example
        </title>

        <para>
          The following convention must be followed for all extensions affecting the host API,
          where TAG can be <constant>KHR</constant>, <constant>EXT</constant> or vendor-specific:
        </para>

        <informaltable frame="none">
            <tgroup cols="1" align="left" colsep="0" rowsep="0">
                <colspec colname="col1" colnum="1" /> <tbody>
                    <row>
                        <entry>#ifndef extension_name
#define extension_name       1

// all data typedefs, token #defines, prototypes, and
// function pointer typedefs for this extension

// function pointer typedefs must use the
// following naming convention
typedef CL_API_ENTRY return type
      (CL_API_CALL *clextension_func_nameTAG_fn)(...);

#endif // extension_name
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>

<para>
Consider, for example, the <citerefentry><refentrytitle>cl_khr_gl_sharing</refentrytitle></citerefentry> extension.
This extension would add the following to <code>cl_gl_ext</code>.h::
</para>
        <informaltable frame="none">
            <tgroup cols="1" align="left" colsep="0" rowsep="0">
                <colspec colname="col1" colnum="1" />
                <tbody>
                    <row>
                        <entry>#ifndef cl_khr_gl_sharing
#define cl_khr_gl_sharing     1

// all data typedefs, token #defines, prototypes, and
// function pointer typedefs for this extension
#define CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR -1000
#define CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR   0x2006
#define CL_DEVICES_FOR_GL_CONTEXT_KHR          0x2007
#define CL_GL_CONTEXT_KHR                      0x2008
#define CL_EGL_DISPLAY_KHR                     0x2009
#define CL_GLX_DISPLAY_KHR                     0x200A
#define CL_WGL_HDC_KHR                         0x200B
#define CL_CGL_SHAREGROUP_KHR                  0x200C

// function pointer typedefs must use the
// following naming convention
typedef CL_API_ENTRY cl_int
     (CL_API_CALL *clGetGLContextInfoKHR_fn)(
              const cl_context_properties * /* properties */,
              cl_gl_context_info /* param_name */,
              size_t /* param_value_size */,
              void * /* param_value */,
              size_t * /*param_value_size_ret*/);
#endif // cl_khr_gl_sharing
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect2>

<!-- ================================ SPECIFICATION  -->
<!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page
-->
    <refsect1 id="specification"><title>Specification</title>
        <para>
            <imageobject>
                <imagedata fileref="pdficon_small1.gif" format="gif" />
            </imageobject>

            <olink uri="clGetExtensionFunctionAddressForPlatform">OpenCL Specification</olink>
        </para>
    </refsect1>

<!-- ================================ ALSO SEE  -->

    <refsect1 id="seealso"><title>Also see</title>
        <para>
            <citerefentry><refentrytitle>EXTENSION</refentrytitle></citerefentry>
        </para>
    </refsect1>

<!-- ============================== COPYRIGHT -->
<!-- Content included from copyright.inc.xsl -->

    <refsect3 id="Copyright"><title></title>
        <imageobject>
                <imagedata fileref="KhronosLogo.jpg" format="jpg" />
        </imageobject>
        <para />
    </refsect3>

<!-- 19-Oct-2011 -->
</refentry>