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<title>Using the GNU Compiler Collection (GCC): Deprecated Features</title>

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<a name="Deprecated-Features"></a>
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<a name="Deprecated-Features-1"></a>
<h3 class="section">7.11 Deprecated Features</h3>

<p>In the past, the GNU C++ compiler was extended to experiment with new
features, at a time when the C++ language was still evolving.  Now that
the C++ standard is complete, some of those features are superseded by
superior alternatives.  Using the old features might cause a warning in
some cases that the feature will be dropped in the future.  In other
cases, the feature might be gone already.
</p>
<p>While the list below is not exhaustive, it documents some of the options
that are now deprecated:
</p>
<dl compact="compact">
<dt><code>-fexternal-templates</code></dt>
<dt><code>-falt-external-templates</code></dt>
<dd><p>These are two of the many ways for G++ to implement template
instantiation.  See <a href="Template-Instantiation.html#Template-Instantiation">Template Instantiation</a>.  The C++ standard clearly
defines how template definitions have to be organized across
implementation units.  G++ has an implicit instantiation mechanism that
should work just fine for standard-conforming code.
</p>
</dd>
<dt><code>-fstrict-prototype</code></dt>
<dt><code>-fno-strict-prototype</code></dt>
<dd><p>Previously it was possible to use an empty prototype parameter list to
indicate an unspecified number of parameters (like C), rather than no
parameters, as C++ demands.  This feature has been removed, except where
it is required for backwards compatibility.   See <a href="Backwards-Compatibility.html#Backwards-Compatibility">Backwards Compatibility</a>.
</p></dd>
</dl>

<p>G++ allows a virtual function returning &lsquo;<samp>void *</samp>&rsquo; to be overridden
by one returning a different pointer type.  This extension to the
covariant return type rules is now deprecated and will be removed from a
future version.
</p>
<p>The G++ minimum and maximum operators (&lsquo;<samp>&lt;?</samp>&rsquo; and &lsquo;<samp>&gt;?</samp>&rsquo;) and
their compound forms (&lsquo;<samp>&lt;?=</samp>&rsquo;) and &lsquo;<samp>&gt;?=</samp>&rsquo;) have been deprecated
and are now removed from G++.  Code using these operators should be
modified to use <code>std::min</code> and <code>std::max</code> instead.
</p>
<p>The named return value extension has been deprecated, and is now
removed from G++.
</p>
<p>The use of initializer lists with new expressions has been deprecated,
and is now removed from G++.
</p>
<p>Floating and complex non-type template parameters have been deprecated,
and are now removed from G++.
</p>
<p>The implicit typename extension has been deprecated and is now
removed from G++.
</p>
<p>The use of default arguments in function pointers, function typedefs
and other places where they are not permitted by the standard is
deprecated and will be removed from a future version of G++.
</p>
<p>G++ allows floating-point literals to appear in integral constant expressions,
e.g. &lsquo;<samp> enum E { e = int(2.2 * 3.7) } </samp>&rsquo;
This extension is deprecated and will be removed from a future version.
</p>
<p>G++ allows static data members of const floating-point type to be declared
with an initializer in a class definition. The standard only allows
initializers for static members of const integral types and const
enumeration types so this extension has been deprecated and will be removed
from a future version.
</p>
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