114 lines
5.0 KiB
HTML
114 lines
5.0 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Using the GNU Compiler Collection (GCC): Backwards Compatibility</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): Backwards Compatibility">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Backwards Compatibility">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="C_002b_002b-Extensions.html#C_002b_002b-Extensions" rel="up" title="C++ Extensions">
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<link href="Objective_002dC.html#Objective_002dC" rel="next" title="Objective-C">
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<link href="Deprecated-Features.html#Deprecated-Features" rel="prev" title="Deprecated Features">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Backwards-Compatibility"></a>
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<div class="header">
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<p>
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Previous: <a href="Deprecated-Features.html#Deprecated-Features" accesskey="p" rel="prev">Deprecated Features</a>, Up: <a href="C_002b_002b-Extensions.html#C_002b_002b-Extensions" accesskey="u" rel="up">C++ Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Backwards-Compatibility-1"></a>
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<h3 class="section">7.14 Backwards Compatibility</h3>
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<a name="index-Backwards-Compatibility"></a>
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<a name="index-ARM-_005bAnnotated-C_002b_002b-Reference-Manual_005d"></a>
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<p>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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</p>
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<dl compact="compact">
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<dt><code>For scope</code></dt>
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<dd><p>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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</p>
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</dd>
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<dt><code>Implicit C language</code></dt>
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<dd><p>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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<code>()</code> is treated as an unspecified number of arguments, rather
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than no arguments, as C++ demands.
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</p></dd>
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</dl>
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</body>
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</html>
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