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<title>Debugging with GDB: Decimal Floating Point</title>

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<a name="Decimal-Floating-Point"></a>
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<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>&rsquo;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.
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