138 lines
6.4 KiB
HTML
138 lines
6.4 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- Copyright (C) 1988-2016 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. -->
|
|
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<title>Using the GNU Compiler Collection (GCC): Decimal Float</title>
|
|
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC): Decimal Float">
|
|
<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Decimal Float">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content="makeinfo">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<link href="index.html#Top" rel="start" title="Top">
|
|
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="C-Extensions.html#C-Extensions" rel="up" title="C Extensions">
|
|
<link href="Hex-Floats.html#Hex-Floats" rel="next" title="Hex Floats">
|
|
<link href="Half_002dPrecision.html#Half_002dPrecision" rel="prev" title="Half-Precision">
|
|
<style type="text/css">
|
|
<!--
|
|
a.summary-letter {text-decoration: none}
|
|
blockquote.smallquotation {font-size: smaller}
|
|
div.display {margin-left: 3.2em}
|
|
div.example {margin-left: 3.2em}
|
|
div.indentedblock {margin-left: 3.2em}
|
|
div.lisp {margin-left: 3.2em}
|
|
div.smalldisplay {margin-left: 3.2em}
|
|
div.smallexample {margin-left: 3.2em}
|
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
|
div.smalllisp {margin-left: 3.2em}
|
|
kbd {font-style:oblique}
|
|
pre.display {font-family: inherit}
|
|
pre.format {font-family: inherit}
|
|
pre.menu-comment {font-family: serif}
|
|
pre.menu-preformatted {font-family: serif}
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
|
pre.smallexample {font-size: smaller}
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
|
pre.smalllisp {font-size: smaller}
|
|
span.nocodebreak {white-space:nowrap}
|
|
span.nolinebreak {white-space:nowrap}
|
|
span.roman {font-family:serif; font-weight:normal}
|
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
|
ul.no-bullet {list-style: none}
|
|
-->
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
|
<a name="Decimal-Float"></a>
|
|
<div class="header">
|
|
<p>
|
|
Next: <a href="Hex-Floats.html#Hex-Floats" accesskey="n" rel="next">Hex Floats</a>, Previous: <a href="Half_002dPrecision.html#Half_002dPrecision" accesskey="p" rel="prev">Half-Precision</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<a name="Decimal-Floating-Types"></a>
|
|
<h3 class="section">6.13 Decimal Floating Types</h3>
|
|
<a name="index-decimal-floating-types"></a>
|
|
<a name="index-_005fDecimal32-data-type"></a>
|
|
<a name="index-_005fDecimal64-data-type"></a>
|
|
<a name="index-_005fDecimal128-data-type"></a>
|
|
<a name="index-df-integer-suffix"></a>
|
|
<a name="index-dd-integer-suffix"></a>
|
|
<a name="index-dl-integer-suffix"></a>
|
|
<a name="index-DF-integer-suffix"></a>
|
|
<a name="index-DD-integer-suffix"></a>
|
|
<a name="index-DL-integer-suffix"></a>
|
|
|
|
<p>As an extension, GNU C supports decimal floating types as
|
|
defined in the N1312 draft of ISO/IEC WDTR24732. Support for decimal
|
|
floating types in GCC will evolve as the draft technical report changes.
|
|
Calling conventions for any target might also change. Not all targets
|
|
support decimal floating types.
|
|
</p>
|
|
<p>The decimal floating types are <code>_Decimal32</code>, <code>_Decimal64</code>, and
|
|
<code>_Decimal128</code>. They use a radix of ten, unlike the floating types
|
|
<code>float</code>, <code>double</code>, and <code>long double</code> whose radix is not
|
|
specified by the C standard but is usually two.
|
|
</p>
|
|
<p>Support for decimal floating types includes the arithmetic operators
|
|
add, subtract, multiply, divide; unary arithmetic operators;
|
|
relational operators; equality operators; and conversions to and from
|
|
integer and other floating types. Use a suffix ‘<samp>df</samp>’ or
|
|
‘<samp>DF</samp>’ in a literal constant of type <code>_Decimal32</code>, ‘<samp>dd</samp>’
|
|
or ‘<samp>DD</samp>’ for <code>_Decimal64</code>, and ‘<samp>dl</samp>’ or ‘<samp>DL</samp>’ for
|
|
<code>_Decimal128</code>.
|
|
</p>
|
|
<p>GCC support of decimal float as specified by the draft technical report
|
|
is incomplete:
|
|
</p>
|
|
<ul>
|
|
<li> When the value of a decimal floating type cannot be represented in the
|
|
integer type to which it is being converted, the result is undefined
|
|
rather than the result value specified by the draft technical report.
|
|
|
|
</li><li> GCC does not provide the C library functionality associated with
|
|
<samp>math.h</samp>, <samp>fenv.h</samp>, <samp>stdio.h</samp>, <samp>stdlib.h</samp>, and
|
|
<samp>wchar.h</samp>, which must come from a separate C library implementation.
|
|
Because of this the GNU C compiler does not define macro
|
|
<code>__STDC_DEC_FP__</code> to indicate that the implementation conforms to
|
|
the technical report.
|
|
</li></ul>
|
|
|
|
<p>Types <code>_Decimal32</code>, <code>_Decimal64</code>, and <code>_Decimal128</code>
|
|
are supported by the DWARF debug information format.
|
|
</p>
|
|
<hr>
|
|
<div class="header">
|
|
<p>
|
|
Next: <a href="Hex-Floats.html#Hex-Floats" accesskey="n" rel="next">Hex Floats</a>, Previous: <a href="Half_002dPrecision.html#Half_002dPrecision" accesskey="p" rel="prev">Half-Precision</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|