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| <h3 class="section">7.12 Backwards Compatibility</h3> |
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| <p><a name="index-Backwards-Compatibility-3191"></a><a name="index-ARM-_005bAnnotated-C_002b_002b-Reference-Manual_005d-3192"></a> |
| Now that there is a definitive ISO standard C++, G++ has a specification |
| to adhere to. The C++ language evolved over time, and features that |
| used to be acceptable in previous drafts of the standard, such as the ARM |
| [Annotated C++ Reference Manual], are no longer accepted. In order to allow |
| compilation of C++ written to such drafts, G++ contains some backwards |
| compatibilities. <em>All such backwards compatibility features are |
| liable to disappear in future versions of G++.</em> They should be considered |
| deprecated. See <a href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>. |
| |
| <dl> |
| <dt><code>For scope</code><dd>If a variable is declared at for scope, it used to remain in scope until |
| the end of the scope which contained the for statement (rather than just |
| within the for scope). G++ retains this, but issues a warning, if such a |
| variable is accessed outside the for scope. |
| |
| <br><dt><code>Implicit C language</code><dd>Old C system header files did not contain an <code>extern "C" {...}</code> |
| scope to set the language. On such systems, all header files are |
| implicitly scoped inside a C language scope. Also, an empty prototype |
| <code>()</code> will be treated as an unspecified number of arguments, rather |
| than no arguments, as C++ demands. |
| </dl> |
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