74 lines
3.4 KiB
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74 lines
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<title>Decimal Floating Point - Debugging with GDB</title>
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<a name="Decimal-Floating-Point"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus">Debugging C Plus Plus</a>,
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<h5 class="subsubsection">15.4.1.8 Decimal Floating Point format</h5>
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<p><a name="index-decimal-floating-point-format-1012"></a>
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<span class="sc">gdb</span> can examine, set and perform computations with numbers in
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decimal floating point format, which in the C language correspond to the
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<code>_Decimal32</code>, <code>_Decimal64</code> and <code>_Decimal128</code> types as
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specified by the extension to support decimal floating-point arithmetic.
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<p>There are two encodings in use, depending on the architecture: BID (Binary
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Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
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PowerPC and S/390. <span class="sc">gdb</span> will use the appropriate encoding for the
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configured target.
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<p>Because of a limitation in <samp><span class="file">libdecnumber</span></samp>, the library used by <span class="sc">gdb</span>
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to manipulate decimal floating point numbers, it is not possible to convert
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(using a cast, for example) integers wider than 32-bit to decimal float.
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<p>In addition, in order to imitate <span class="sc">gdb</span>'s behaviour with binary floating
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point computations, error checking in decimal float operations ignores
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underflow, overflow and divide by zero exceptions.
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<p>In the PowerPC architecture, <span class="sc">gdb</span> provides a set of pseudo-registers
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to inspect <code>_Decimal128</code> values stored in floating point registers.
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See <a href="PowerPC.html#PowerPC">PowerPC</a> for more details.
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</body></html>
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