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<h2 class="chapter">7 Extensions to the C++ Language</h2>
<p><a name="index-extensions_002c-C_002b_002b-language-4197"></a><a name="index-C_002b_002b-language-extensions-4198"></a>
The GNU compiler provides these extensions to the C++ language (and you
can also use most of the C language extensions in your C++ programs). If you
want to write code that checks whether these features are available, you can
test for the GNU compiler the same way as for C programs: check for a
predefined macro <code>__GNUC__</code>. You can also use <code>__GNUG__</code> to
test specifically for GNU C++ (see <a href="../cpp/Common-Predefined-Macros.html#Common-Predefined-Macros">Predefined Macros</a>).
<ul class="menu">
<li><a accesskey="1" href="C_002b_002b-Volatiles.html#C_002b_002b-Volatiles">C++ Volatiles</a>: What constitutes an access to a volatile object.
<li><a accesskey="2" href="Restricted-Pointers.html#Restricted-Pointers">Restricted Pointers</a>: C99 restricted pointers and references.
<li><a accesskey="3" href="Vague-Linkage.html#Vague-Linkage">Vague Linkage</a>: Where G++ puts inlines, vtables and such.
<li><a accesskey="4" href="C_002b_002b-Interface.html#C_002b_002b-Interface">C++ Interface</a>: You can use a single C++ header file for both
declarations and definitions.
<li><a accesskey="5" href="Template-Instantiation.html#Template-Instantiation">Template Instantiation</a>: Methods for ensuring that exactly one copy of
each needed template instantiation is emitted.
<li><a accesskey="6" href="Bound-member-functions.html#Bound-member-functions">Bound member functions</a>: You can extract a function pointer to the
method denoted by a ‘<samp><span class="samp">->*</span></samp>’ or ‘<samp><span class="samp">.*</span></samp>’ expression.
<li><a accesskey="7" href="C_002b_002b-Attributes.html#C_002b_002b-Attributes">C++ Attributes</a>: Variable, function, and type attributes for C++ only.
<li><a accesskey="8" href="Function-Multiversioning.html#Function-Multiversioning">Function Multiversioning</a>: Declaring multiple function versions.
<li><a accesskey="9" href="Namespace-Association.html#Namespace-Association">Namespace Association</a>: Strong using-directives for namespace association.
<li><a href="Type-Traits.html#Type-Traits">Type Traits</a>: Compiler support for type traits
<li><a href="Java-Exceptions.html#Java-Exceptions">Java Exceptions</a>: Tweaking exception handling to work with Java.
<li><a href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>: Things will disappear from G++.
<li><a href="Backwards-Compatibility.html#Backwards-Compatibility">Backwards Compatibility</a>: Compatibilities with earlier definitions of C++.
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