<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Copyright (C) 1988-2019 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 "Free Software" and "Free Software Needs Free Documentation", with the Front-Cover Texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. (a) The FSF's Back-Cover Text is: "You are free to copy and modify this GNU Manual. Buying copies from GNU Press supports the FSF in developing GNU and promoting software freedom." --> <!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ --> <head> <title>Decimal Floating Point (Debugging with GDB)</title> <meta name="description" content="Decimal Floating Point (Debugging with GDB)"> <meta name="keywords" content="Decimal Floating Point (Debugging with GDB)"> <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="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="C.html#C" rel="up" title="C"> <link href="D.html#D" rel="next" title="D"> <link href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus" rel="prev" title="Debugging C Plus Plus"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} 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.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <a name="Decimal-Floating-Point"></a> <div class="header"> <p> Previous: <a href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus" accesskey="p" rel="prev">Debugging C Plus Plus</a>, Up: <a href="C.html#C" accesskey="u" rel="up">C</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> </div> <hr> <a name="Decimal-Floating-Point-format"></a> <h4 class="subsubsection">15.4.1.8 Decimal Floating Point format</h4> <a name="index-decimal-floating-point-format"></a> <p><small>GDB</small> can examine, set and perform computations with numbers in decimal floating point format, which in the C language correspond to the <code>_Decimal32</code>, <code>_Decimal64</code> and <code>_Decimal128</code> types as specified by the extension to support decimal floating-point arithmetic. </p> <p>There are two encodings in use, depending on the architecture: BID (Binary Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for PowerPC and S/390. <small>GDB</small> will use the appropriate encoding for the configured target. </p> <p>Because of a limitation in <samp>libdecnumber</samp>, the library used by <small>GDB</small> to manipulate decimal floating point numbers, it is not possible to convert (using a cast, for example) integers wider than 32-bit to decimal float. </p> <p>In addition, in order to imitate <small>GDB</small>’s behaviour with binary floating point computations, error checking in decimal float operations ignores underflow, overflow and divide by zero exceptions. </p> <p>In the PowerPC architecture, <small>GDB</small> provides a set of pseudo-registers to inspect <code>_Decimal128</code> values stored in floating point registers. See <a href="PowerPC.html#PowerPC">PowerPC</a> for more details. </p> </body> </html>