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85 lines
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85 lines
4.0 KiB
HTML
4 years ago
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<title>Backwards Compatibility - Using the GNU Compiler Collection (GCC)</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions" title="C++ Extensions">
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<link rel="prev" href="Deprecated-Features.html#Deprecated-Features" title="Deprecated Features">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Backwards-Compatibility"></a>
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<p>
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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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<hr>
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</div>
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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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<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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</dl>
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<!-- LocalWords: emph deftypefn builtin ARCv2EM SIMD builtins msimd -->
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<!-- LocalWords: typedef v4si v8hi DMA dma vdiwr vdowr -->
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<!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. -->
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<!-- This is part of the GCC manual. -->
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<!-- For copying conditions, see the file gcc.texi. -->
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</body></html>
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