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118 lines
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<title>Deprecated Features - Using the GNU Compiler Collection (GCC)</title>
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<a name="Deprecated-Features"></a>
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Next: <a rel="next" accesskey="n" href="Backwards-Compatibility.html#Backwards-Compatibility">Backwards Compatibility</a>,
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Previous: <a rel="previous" accesskey="p" href="Java-Exceptions.html#Java-Exceptions">Java Exceptions</a>,
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Up: <a rel="up" accesskey="u" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions">C++ Extensions</a>
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</div>
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<h3 class="section">7.12 Deprecated Features</h3>
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<p>In the past, the GNU C++ compiler was extended to experiment with new
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features, at a time when the C++ language was still evolving. Now that
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the C++ standard is complete, some of those features are superseded by
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superior alternatives. Using the old features might cause a warning in
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some cases that the feature will be dropped in the future. In other
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cases, the feature might be gone already.
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<p>While the list below is not exhaustive, it documents some of the options
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that are now deprecated:
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<dl>
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<dt><code>-fexternal-templates</code><dt><code>-falt-external-templates</code><dd>These are two of the many ways for G++ to implement template
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instantiation. See <a href="Template-Instantiation.html#Template-Instantiation">Template Instantiation</a>. The C++ standard clearly
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defines how template definitions have to be organized across
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implementation units. G++ has an implicit instantiation mechanism that
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should work just fine for standard-conforming code.
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<br><dt><code>-fstrict-prototype</code><dt><code>-fno-strict-prototype</code><dd>Previously it was possible to use an empty prototype parameter list to
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indicate an unspecified number of parameters (like C), rather than no
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parameters, as C++ demands. This feature has been removed, except where
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it is required for backwards compatibility. See <a href="Backwards-Compatibility.html#Backwards-Compatibility">Backwards Compatibility</a>.
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</dl>
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<p>G++ allows a virtual function returning ‘<samp><span class="samp">void *</span></samp>’ to be overridden
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by one returning a different pointer type. This extension to the
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covariant return type rules is now deprecated and will be removed from a
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future version.
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<p>The G++ minimum and maximum operators (‘<samp><span class="samp"><?</span></samp>’ and ‘<samp><span class="samp">>?</span></samp>’) and
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their compound forms (‘<samp><span class="samp"><?=</span></samp>’) and ‘<samp><span class="samp">>?=</span></samp>’) have been deprecated
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and are now removed from G++. Code using these operators should be
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modified to use <code>std::min</code> and <code>std::max</code> instead.
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<p>The named return value extension has been deprecated, and is now
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removed from G++.
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<p>The use of initializer lists with new expressions has been deprecated,
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and is now removed from G++.
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<p>Floating and complex non-type template parameters have been deprecated,
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and are now removed from G++.
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<p>The implicit typename extension has been deprecated and is now
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removed from G++.
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<p>The use of default arguments in function pointers, function typedefs
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and other places where they are not permitted by the standard is
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deprecated and will be removed from a future version of G++.
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<p>G++ allows floating-point literals to appear in integral constant expressions,
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e.g. ‘<samp><span class="samp"> enum E { e = int(2.2 * 3.7) } </span></samp>’
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This extension is deprecated and will be removed from a future version.
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<p>G++ allows static data members of const floating-point type to be declared
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with an initializer in a class definition. The standard only allows
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initializers for static members of const integral types and const
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enumeration types so this extension has been deprecated and will be removed
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from a future version.
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</body></html>
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