devdocs/gcc~13/backwards-compatibility.html


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<div class="section-level-extent" id="Backwards-Compatibility"> <div class="nav-panel"> <p> Previous: <a href="deprecated-features" accesskey="p" rel="prev">Deprecated Features</a>, Up: <a href="c_002b_002b-extensions" accesskey="u" rel="up">Extensions to the C++ Language</a> [<a href="index#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="indices" title="Index" rel="index">Index</a>]</p> </div>  <h1 class="section" id="Backwards-Compatibility-1"><span>7.12 Backwards Compatibility<a class="copiable-link" href="#Backwards-Compatibility-1"> ¶</a></span></h1>   <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 class="emph">All such backwards compatibility features are liable to disappear in future versions of G++.</em> They should be considered deprecated. See <a class="xref" href="deprecated-features">Deprecated Features</a>. </p> <dl class="table"> <dt><code class="code">Implicit C language</code></dt> <dd>
<p>Old C system header files did not contain an <code class="code">extern "C" {…}</code> scope to set the language. On such systems, all system header files are implicitly scoped inside a C language scope. Such headers must correctly prototype function argument types, there is no leeway for <code class="code">()</code> to indicate an unspecified set of arguments. </p> </dd> </dl> </div><div class="_attribution">
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