<html lang="en">
<head>
<title>Backwards Compatibility - 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 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions" title="C++ Extensions">
<link rel="prev" href="Deprecated-Features.html#Deprecated-Features" title="Deprecated Features">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988-2015 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Funding Free Software'', the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below). A copy of the license is included in the section entitled
``GNU Free Documentation License''.
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
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 }
span.sc { font-variant:small-caps }
span.roman { font-family:serif; font-weight:normal; }
span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<a name="Backwards-Compatibility"></a>
<p>
Previous: <a rel="previous" accesskey="p" href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>,
Up: <a rel="up" accesskey="u" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions">C++ Extensions</a>
<hr>
</div>
<h3 class="section">7.13 Backwards Compatibility</h3>
<p><a name="index-Backwards-Compatibility-4236"></a><a name="index-ARM-_005bAnnotated-C_002b_002b-Reference-Manual_005d-4237"></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 that 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> is treated as an unspecified number of arguments, rather
than no arguments, as C++ demands.
</dl>
<!-- LocalWords: emph deftypefn builtin ARCv2EM SIMD builtins msimd -->
<!-- LocalWords: typedef v4si v8hi DMA dma vdiwr vdowr -->
<!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. -->
<!-- This is part of the GCC manual. -->
<!-- For copying conditions, see the file gcc.texi. -->
</body></html>