1<html lang="en"> 2<head> 3<title>Decimal Float - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> 9<link rel="prev" href="Half_002dPrecision.html#Half_002dPrecision" title="Half-Precision"> 10<link rel="next" href="Hex-Floats.html#Hex-Floats" title="Hex Floats"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). 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Support for decimal 63floating types in GCC will evolve as the draft technical report changes. 64Calling conventions for any target might also change. Not all targets 65support decimal floating types. 66 67 <p>The decimal floating types are <code>_Decimal32</code>, <code>_Decimal64</code>, and 68<code>_Decimal128</code>. They use a radix of ten, unlike the floating types 69<code>float</code>, <code>double</code>, and <code>long double</code> whose radix is not 70specified by the C standard but is usually two. 71 72 <p>Support for decimal floating types includes the arithmetic operators 73add, subtract, multiply, divide; unary arithmetic operators; 74relational operators; equality operators; and conversions to and from 75integer and other floating types. Use a suffix ‘<samp><span class="samp">df</span></samp>’ or 76‘<samp><span class="samp">DF</span></samp>’ in a literal constant of type <code>_Decimal32</code>, ‘<samp><span class="samp">dd</span></samp>’ 77or ‘<samp><span class="samp">DD</span></samp>’ for <code>_Decimal64</code>, and ‘<samp><span class="samp">dl</span></samp>’ or ‘<samp><span class="samp">DL</span></samp>’ for 78<code>_Decimal128</code>. 79 80 <p>GCC support of decimal float as specified by the draft technical report 81is incomplete: 82 83 <ul> 84<li>When the value of a decimal floating type cannot be represented in the 85integer type to which it is being converted, the result is undefined 86rather than the result value specified by the draft technical report. 87 88 <li>GCC does not provide the C library functionality associated with 89<samp><span class="file">math.h</span></samp>, <samp><span class="file">fenv.h</span></samp>, <samp><span class="file">stdio.h</span></samp>, <samp><span class="file">stdlib.h</span></samp>, and 90<samp><span class="file">wchar.h</span></samp>, which must come from a separate C library implementation. 91Because of this the GNU C compiler does not define macro 92<code>__STDC_DEC_FP__</code> to indicate that the implementation conforms to 93the technical report. 94</ul> 95 96 <p>Types <code>_Decimal32</code>, <code>_Decimal64</code>, and <code>_Decimal128</code> 97are supported by the DWARF2 debug information format. 98 99 </body></html> 100 101