📄 backwards-compatibility.html
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Node:<a name="Backwards%20Compatibility">Backwards Compatibility</a>,
Previous:<a rel="previous" accesskey="p" href="Deprecated-Features.html#Deprecated%20Features">Deprecated Features</a>,
Up:<a rel="up" accesskey="u" href="C---Extensions.html#C++%20Extensions">C++ Extensions</a>
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<h3 class="section">Backwards Compatibility</h3>
<p>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%20Features">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.
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