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17<title>Debugging with GDB: Decimal Floating Point</title>
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67Previous: <a href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus" accesskey="p" rel="previous">Debugging C Plus Plus</a>, Up: <a href="C.html#C" accesskey="u" rel="up">C</a> &nbsp; [<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>
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70<a name="Decimal-Floating-Point-Format"></a>
71<h4 class="subsubsection">15.4.1.8 Decimal Floating Point Format</h4>
72<a name="index-decimal-floating-point-format"></a>
73
74<p><small>GDB</small> can examine, set and perform computations with numbers in
75decimal floating point format, which in the C language correspond to the
76<code>_Decimal32</code>, <code>_Decimal64</code> and <code>_Decimal128</code> types as
77specified by the extension to support decimal floating-point arithmetic.
78</p>
79<p>There are two encodings in use, depending on the architecture: BID (Binary
80Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
81PowerPC and S/390.  <small>GDB</small> will use the appropriate encoding for the
82configured target.
83</p>
84<p>Because of a limitation in <samp>libdecnumber</samp>, the library used by <small>GDB</small>
85to manipulate decimal floating point numbers, it is not possible to convert
86(using a cast, for example) integers wider than 32-bit to decimal float.
87</p>
88<p>In addition, in order to imitate <small>GDB</small>&rsquo;s behaviour with binary floating
89point computations, error checking in decimal float operations ignores
90underflow, overflow and divide by zero exceptions.
91</p>
92<p>In the PowerPC architecture, <small>GDB</small> provides a set of pseudo-registers
93to inspect <code>_Decimal128</code> values stored in floating point registers.
94See <a href="PowerPC.html#PowerPC">PowerPC</a> for more details.
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