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<a name="Backwards-Compatibility"></a>
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Previous: <a rel="previous" accesskey="p" href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</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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<h3 class="section">7.13 Backwards Compatibility</h3>
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<p><a name="index-Backwards-Compatibility-4236"></a><a name="index-ARM-_005bAnnotated-C_002b_002b-Reference-Manual_005d-4237"></a>
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Now that there is a definitive ISO standard C++, G++ has a specification
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to adhere to. The C++ language evolved over time, and features that
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used to be acceptable in previous drafts of the standard, such as the ARM
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[Annotated C++ Reference Manual], are no longer accepted. In order to allow
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compilation of C++ written to such drafts, G++ contains some backwards
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compatibilities. <em>All such backwards compatibility features are
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liable to disappear in future versions of G++.</em> They should be considered
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deprecated. See <a href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>.
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<dl>
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<dt><code>For scope</code><dd>If a variable is declared at for scope, it used to remain in scope until
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the end of the scope that contained the for statement (rather than just
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within the for scope). G++ retains this, but issues a warning, if such a
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variable is accessed outside the for scope.
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<br><dt><code>Implicit C language</code><dd>Old C system header files did not contain an <code>extern "C" {...}</code>
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scope to set the language. On such systems, all header files are
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implicitly scoped inside a C language scope. Also, an empty prototype
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than no arguments, as C++ demands.
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