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95 lines
4.0 KiB
HTML
95 lines
4.0 KiB
HTML
4 years ago
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>va_arg (The Red Hat newlib C Library)</title>
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<meta name="description" content="va_arg (The Red Hat newlib C Library)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Document-Index.html#Document-Index" rel="index" title="Document Index">
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Stdarg.html#Stdarg" rel="up" title="Stdarg">
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<link href="va_005fend.html#va_005fend" rel="next" title="va_end">
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</head>
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<body lang="en">
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<a name="va_005farg"></a>
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<div class="header">
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<p>
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Next: <a href="va_005fend.html#va_005fend" accesskey="n" rel="next">va_end</a>, Previous: <a href="va_005fstart.html#va_005fstart" accesskey="p" rel="prev">va_start</a>, Up: <a href="Stdarg.html#Stdarg" accesskey="u" rel="up">Stdarg</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Extract-a-value-from-argument-list"></a>
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<h4 class="subsection">14.1.2 Extract a value from argument list</h4>
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<a name="index-va_005farg"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <stdarg.h>
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<var>type</var> va_arg(va_list <var>ap</var>, <var>type</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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<code>va_arg</code> returns the next unprocessed value from a variable
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argument list <var>ap</var> (which you must previously create with
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<var>va_start</var>). Specify the type for the value as the second parameter
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to the macro, <var>type</var>.
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</p>
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<p>You may pass a <code>va_list</code> object <var>ap</var> to a subfunction, and use
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<code>va_arg</code> from the subfunction rather than from the function
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actually declared with an ellipsis in the header; however, in that case
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you may <em>only</em> use <code>va_arg</code> from the subfunction. ANSI C does
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not permit extracting successive values from a single variable-argument
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list from different levels of the calling stack.
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</p>
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<p>There is no mechanism for testing whether there is actually a next
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argument available; you might instead pass an argument count (or some
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other data that implies an argument count) as one of the fixed arguments
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in your function call.
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</p>
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<p><strong>Returns</strong><br>
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<code>va_arg</code> returns the next argument, an object of type <var>type</var>.
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</p>
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<p><strong>Portability</strong><br>
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ANSI C requires <code>va_arg</code>.
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</p>
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</body>
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