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<html lang="en"><head><title>Using the GNU Compiler Collection (GCC)</title><meta http-equiv="Content-Type" content="text/html"><meta name="description" content="Using the GNU Compiler Collection (GCC)"><meta name="generator" content="makeinfo 4.6"><!--Copyright © 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. <p>Permission is granted to copy, distribute and/or modify this documentunder the terms of the GNU Free Documentation License, Version 1.2 orany later version published by the Free Software Foundation; with theInvariant Sections being "GNU General Public License" and "FundingFree Software", the Front-Cover texts being (a) (see below), and withthe Back-Cover Texts being (b) (see below). A copy of the license isincluded in the section entitled "GNU Free Documentation License". <p>(a) The FSF's Front-Cover Text is: <p>A GNU Manual <p>(b) The FSF's Back-Cover Text is: <p>You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.--><meta http-equiv="Content-Style-Type" content="text/css"><style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller }--></style></head><body><div class="node"><p>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><hr><br></div><h3 class="section">Backwards Compatibility</h3><p>Now that there is a definitive ISO standard C++, G++ has a specificationto adhere to. The C++ language evolved over time, and features thatused to be acceptable in previous drafts of the standard, such as the ARM[Annotated C++ Reference Manual], are no longer accepted. In order to allowcompilation of C++ written to such drafts, G++ contains some backwardscompatibilities. <em>All such backwards compatibility features areliable to disappear in future versions of G++.</em> They should be considereddeprecated 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 untilthe end of the scope which contained the for statement (rather than justwithin the for scope). G++ retains this, but issues a warning, if such avariable 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 areimplicitly scoped inside a C language scope. Also, an empty prototype<code>()</code> will be treated as an unspecified number of arguments, ratherthan no arguments, as C++ demands. </dl> </body></html>⌨️ 快捷键说明
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