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103 lines
4.2 KiB
HTML
103 lines
4.2 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>version (LIBM)</title>
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<meta name="description" content="version (LIBM)">
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<meta name="keywords" content="version (LIBM)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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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="Math.html#Math" rel="up" title="Math">
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<link href="acos.html#acos" rel="next" title="acos">
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<link href="Math.html#Math" rel="prev" title="Math">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="version"></a>
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<div class="header">
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<p>
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Next: <a href="acos.html#acos" accesskey="n" rel="next">acos</a>, Up: <a href="Math.html#Math" accesskey="u" rel="up">Math</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="Error-Handling"></a>
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<h3 class="section">1.1 Error Handling</h3>
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<p>There are two different versions of the math library routines: IEEE
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and POSIX. The version may be selected at runtime by
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setting the global variable <code>_LIB_VERSION</code>, defined in
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<samp>math.h</samp>. It may be set to one of the following constants defined
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in <samp>math.h</samp>: <code>_IEEE_</code> or <code>_POSIX_</code>.
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The <code>_LIB_VERSION</code> variable is not specific to any
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thread, and changing it will affect all threads.
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</p>
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<p>The versions of the library differ only in the setting of <code>errno</code>.
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</p>
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<p>In IEEE mode, <code>errno</code> is never set.
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</p>
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<p>In POSIX mode, <code>errno</code> is set correctly.
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</p>
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<p>The library is set to IEEE mode by default.
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</p>
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<p>The majority of the floating-point math functions are written
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so as to produce the floating-point exceptions (e.g. "invalid",
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"divide-by-zero") as required by the C and POSIX standards, for
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floating-point implementations that support them. Newlib does not provide
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the floating-point exception access routines defined in the standards
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for fenv.h, though, which is why they are considered unsupported. It is
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mentioned in case you have separately-provided access routines so that
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you are aware that they can be caused.
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</p>
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<a name="Standards-Compliance-And-Portability"></a>
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<h3 class="section">1.2 Standards Compliance And Portability</h3>
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<p>Most of the individual function descriptions describe the standards to which
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each function complies. However, these descriptions are mostly out of date,
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having been written before C99 was released. One of these days we’ll get
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around to updating the rest of them. (If you’d like to help, please let us
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know.)
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</p>
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<p>“C99” refers to ISO/IEC 9899:1999, “Programming languages–C”.
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“POSIX” refers to IEEE Standard 1003.1. POSIX® is a
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registered trademark of The IEEE.
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</p>
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</body>
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</html>
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