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<title>Using the GNU Compiler Collection (GCC): Fixed-Point</title>
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<a name="Fixed_002dPoint"></a>
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<p>
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Next: <a href="Named-Address-Spaces.html#Named-Address-Spaces" accesskey="n" rel="next">Named Address Spaces</a>, Previous: <a href="Hex-Floats.html#Hex-Floats" accesskey="p" rel="prev">Hex Floats</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Fixed_002dPoint-Types"></a>
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<h3 class="section">6.15 Fixed-Point Types</h3>
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<a name="index-fixed_002dpoint-types"></a>
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<a name="index-_005fFract-data-type"></a>
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<a name="index-_005fAccum-data-type"></a>
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<a name="index-_005fSat-data-type"></a>
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<a name="index-hr-fixed_002dsuffix"></a>
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<a name="index-r-fixed_002dsuffix"></a>
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<p>As an extension, GNU C supports fixed-point types as
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defined in the N1169 draft of ISO/IEC DTR 18037. Support for fixed-point
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types in GCC will evolve as the draft technical report changes.
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Calling conventions for any target might also change. Not all targets
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support fixed-point types.
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</p>
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<p>The fixed-point types are
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<code>short _Fract</code>,
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<code>_Fract</code>,
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<code>long _Fract</code>,
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<code>long long _Fract</code>,
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<code>unsigned short _Fract</code>,
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<code>unsigned _Fract</code>,
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<code>unsigned long _Fract</code>,
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<code>unsigned long long _Fract</code>,
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<code>_Sat short _Fract</code>,
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<code>_Sat _Fract</code>,
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<code>_Sat long _Fract</code>,
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<code>_Sat long long _Fract</code>,
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<code>_Sat unsigned short _Fract</code>,
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<code>_Sat unsigned _Fract</code>,
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<code>_Sat unsigned long _Fract</code>,
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<code>_Sat unsigned long long _Fract</code>,
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<code>short _Accum</code>,
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<code>_Accum</code>,
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<code>long _Accum</code>,
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<code>long long _Accum</code>,
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<code>unsigned short _Accum</code>,
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<code>unsigned _Accum</code>,
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<code>unsigned long _Accum</code>,
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<code>unsigned long long _Accum</code>,
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<code>_Sat short _Accum</code>,
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<code>_Sat _Accum</code>,
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<code>_Sat long _Accum</code>,
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<code>_Sat long long _Accum</code>,
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<code>_Sat unsigned short _Accum</code>,
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<code>_Sat unsigned _Accum</code>,
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<code>_Sat unsigned long _Accum</code>,
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<code>_Sat unsigned long long _Accum</code>.
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</p>
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<p>Fixed-point data values contain fractional and optional integral parts.
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The format of fixed-point data varies and depends on the target machine.
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</p>
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<p>Support for fixed-point types includes:
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</p><ul>
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<li> prefix and postfix increment and decrement operators (<code>++</code>, <code>--</code>)
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</li><li> unary arithmetic operators (<code>+</code>, <code>-</code>, <code>!</code>)
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</li><li> binary arithmetic operators (<code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>)
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</li><li> binary shift operators (<code><<</code>, <code>>></code>)
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</li><li> relational operators (<code><</code>, <code><=</code>, <code>>=</code>, <code>></code>)
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</li><li> equality operators (<code>==</code>, <code>!=</code>)
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</li><li> assignment operators (<code>+=</code>, <code>-=</code>, <code>*=</code>, <code>/=</code>,
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<code><<=</code>, <code>>>=</code>)
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</li><li> conversions to and from integer, floating-point, or fixed-point types
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</li></ul>
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<p>Use a suffix in a fixed-point literal constant:
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</p><ul>
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<li> ‘<samp>hr</samp>’ or ‘<samp>HR</samp>’ for <code>short _Fract</code> and
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<code>_Sat short _Fract</code>
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</li><li> ‘<samp>r</samp>’ or ‘<samp>R</samp>’ for <code>_Fract</code> and <code>_Sat _Fract</code>
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</li><li> ‘<samp>lr</samp>’ or ‘<samp>LR</samp>’ for <code>long _Fract</code> and
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<code>_Sat long _Fract</code>
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</li><li> ‘<samp>llr</samp>’ or ‘<samp>LLR</samp>’ for <code>long long _Fract</code> and
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<code>_Sat long long _Fract</code>
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</li><li> ‘<samp>uhr</samp>’ or ‘<samp>UHR</samp>’ for <code>unsigned short _Fract</code> and
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<code>_Sat unsigned short _Fract</code>
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</li><li> ‘<samp>ur</samp>’ or ‘<samp>UR</samp>’ for <code>unsigned _Fract</code> and
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<code>_Sat unsigned _Fract</code>
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</li><li> ‘<samp>ulr</samp>’ or ‘<samp>ULR</samp>’ for <code>unsigned long _Fract</code> and
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<code>_Sat unsigned long _Fract</code>
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</li><li> ‘<samp>ullr</samp>’ or ‘<samp>ULLR</samp>’ for <code>unsigned long long _Fract</code>
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and <code>_Sat unsigned long long _Fract</code>
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</li><li> ‘<samp>hk</samp>’ or ‘<samp>HK</samp>’ for <code>short _Accum</code> and
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<code>_Sat short _Accum</code>
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</li><li> ‘<samp>k</samp>’ or ‘<samp>K</samp>’ for <code>_Accum</code> and <code>_Sat _Accum</code>
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</li><li> ‘<samp>lk</samp>’ or ‘<samp>LK</samp>’ for <code>long _Accum</code> and
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<code>_Sat long _Accum</code>
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</li><li> ‘<samp>llk</samp>’ or ‘<samp>LLK</samp>’ for <code>long long _Accum</code> and
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<code>_Sat long long _Accum</code>
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</li><li> ‘<samp>uhk</samp>’ or ‘<samp>UHK</samp>’ for <code>unsigned short _Accum</code> and
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<code>_Sat unsigned short _Accum</code>
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</li><li> ‘<samp>uk</samp>’ or ‘<samp>UK</samp>’ for <code>unsigned _Accum</code> and
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<code>_Sat unsigned _Accum</code>
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</li><li> ‘<samp>ulk</samp>’ or ‘<samp>ULK</samp>’ for <code>unsigned long _Accum</code> and
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<code>_Sat unsigned long _Accum</code>
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</li><li> ‘<samp>ullk</samp>’ or ‘<samp>ULLK</samp>’ for <code>unsigned long long _Accum</code>
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and <code>_Sat unsigned long long _Accum</code>
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</li></ul>
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<p>GCC support of fixed-point types as specified by the draft technical report
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is incomplete:
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</p>
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<ul>
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<li> Pragmas to control overflow and rounding behaviors are not implemented.
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</li></ul>
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<p>Fixed-point types are supported by the DWARF debug information format.
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</p>
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<div class="header">
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<p>
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Next: <a href="Named-Address-Spaces.html#Named-Address-Spaces" accesskey="n" rel="next">Named Address Spaces</a>, Previous: <a href="Hex-Floats.html#Hex-Floats" accesskey="p" rel="prev">Hex Floats</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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