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| <a name="Fixed_002dPoint"></a> |
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| <a name="Fixed_002dPoint-Types"></a> |
| <h3 class="section">6.15 Fixed-Point Types</h3> |
| <a name="index-fixed_002dpoint-types"></a> |
| <a name="index-_005fFract-data-type"></a> |
| <a name="index-_005fAccum-data-type"></a> |
| <a name="index-_005fSat-data-type"></a> |
| <a name="index-hr-fixed_002dsuffix"></a> |
| <a name="index-r-fixed_002dsuffix"></a> |
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| |
| <p>As an extension, GNU C supports fixed-point types as |
| defined in the N1169 draft of ISO/IEC DTR 18037. Support for fixed-point |
| types in GCC will evolve as the draft technical report changes. |
| Calling conventions for any target might also change. Not all targets |
| support fixed-point types. |
| </p> |
| <p>The fixed-point types are |
| <code>short _Fract</code>, |
| <code>_Fract</code>, |
| <code>long _Fract</code>, |
| <code>long long _Fract</code>, |
| <code>unsigned short _Fract</code>, |
| <code>unsigned _Fract</code>, |
| <code>unsigned long _Fract</code>, |
| <code>unsigned long long _Fract</code>, |
| <code>_Sat short _Fract</code>, |
| <code>_Sat _Fract</code>, |
| <code>_Sat long _Fract</code>, |
| <code>_Sat long long _Fract</code>, |
| <code>_Sat unsigned short _Fract</code>, |
| <code>_Sat unsigned _Fract</code>, |
| <code>_Sat unsigned long _Fract</code>, |
| <code>_Sat unsigned long long _Fract</code>, |
| <code>short _Accum</code>, |
| <code>_Accum</code>, |
| <code>long _Accum</code>, |
| <code>long long _Accum</code>, |
| <code>unsigned short _Accum</code>, |
| <code>unsigned _Accum</code>, |
| <code>unsigned long _Accum</code>, |
| <code>unsigned long long _Accum</code>, |
| <code>_Sat short _Accum</code>, |
| <code>_Sat _Accum</code>, |
| <code>_Sat long _Accum</code>, |
| <code>_Sat long long _Accum</code>, |
| <code>_Sat unsigned short _Accum</code>, |
| <code>_Sat unsigned _Accum</code>, |
| <code>_Sat unsigned long _Accum</code>, |
| <code>_Sat unsigned long long _Accum</code>. |
| </p> |
| <p>Fixed-point data values contain fractional and optional integral parts. |
| The format of fixed-point data varies and depends on the target machine. |
| </p> |
| <p>Support for fixed-point types includes: |
| </p><ul> |
| <li> prefix and postfix increment and decrement operators (<code>++</code>, <code>--</code>) |
| </li><li> unary arithmetic operators (<code>+</code>, <code>-</code>, <code>!</code>) |
| </li><li> binary arithmetic operators (<code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>) |
| </li><li> binary shift operators (<code><<</code>, <code>>></code>) |
| </li><li> relational operators (<code><</code>, <code><=</code>, <code>>=</code>, <code>></code>) |
| </li><li> equality operators (<code>==</code>, <code>!=</code>) |
| </li><li> assignment operators (<code>+=</code>, <code>-=</code>, <code>*=</code>, <code>/=</code>, |
| <code><<=</code>, <code>>>=</code>) |
| </li><li> conversions to and from integer, floating-point, or fixed-point types |
| </li></ul> |
| |
| <p>Use a suffix in a fixed-point literal constant: |
| </p><ul> |
| <li> ‘<samp>hr</samp>’ or ‘<samp>HR</samp>’ for <code>short _Fract</code> and |
| <code>_Sat short _Fract</code> |
| </li><li> ‘<samp>r</samp>’ or ‘<samp>R</samp>’ for <code>_Fract</code> and <code>_Sat _Fract</code> |
| </li><li> ‘<samp>lr</samp>’ or ‘<samp>LR</samp>’ for <code>long _Fract</code> and |
| <code>_Sat long _Fract</code> |
| </li><li> ‘<samp>llr</samp>’ or ‘<samp>LLR</samp>’ for <code>long long _Fract</code> and |
| <code>_Sat long long _Fract</code> |
| </li><li> ‘<samp>uhr</samp>’ or ‘<samp>UHR</samp>’ for <code>unsigned short _Fract</code> and |
| <code>_Sat unsigned short _Fract</code> |
| </li><li> ‘<samp>ur</samp>’ or ‘<samp>UR</samp>’ for <code>unsigned _Fract</code> and |
| <code>_Sat unsigned _Fract</code> |
| </li><li> ‘<samp>ulr</samp>’ or ‘<samp>ULR</samp>’ for <code>unsigned long _Fract</code> and |
| <code>_Sat unsigned long _Fract</code> |
| </li><li> ‘<samp>ullr</samp>’ or ‘<samp>ULLR</samp>’ for <code>unsigned long long _Fract</code> |
| and <code>_Sat unsigned long long _Fract</code> |
| </li><li> ‘<samp>hk</samp>’ or ‘<samp>HK</samp>’ for <code>short _Accum</code> and |
| <code>_Sat short _Accum</code> |
| </li><li> ‘<samp>k</samp>’ or ‘<samp>K</samp>’ for <code>_Accum</code> and <code>_Sat _Accum</code> |
| </li><li> ‘<samp>lk</samp>’ or ‘<samp>LK</samp>’ for <code>long _Accum</code> and |
| <code>_Sat long _Accum</code> |
| </li><li> ‘<samp>llk</samp>’ or ‘<samp>LLK</samp>’ for <code>long long _Accum</code> and |
| <code>_Sat long long _Accum</code> |
| </li><li> ‘<samp>uhk</samp>’ or ‘<samp>UHK</samp>’ for <code>unsigned short _Accum</code> and |
| <code>_Sat unsigned short _Accum</code> |
| </li><li> ‘<samp>uk</samp>’ or ‘<samp>UK</samp>’ for <code>unsigned _Accum</code> and |
| <code>_Sat unsigned _Accum</code> |
| </li><li> ‘<samp>ulk</samp>’ or ‘<samp>ULK</samp>’ for <code>unsigned long _Accum</code> and |
| <code>_Sat unsigned long _Accum</code> |
| </li><li> ‘<samp>ullk</samp>’ or ‘<samp>ULLK</samp>’ for <code>unsigned long long _Accum</code> |
| and <code>_Sat unsigned long long _Accum</code> |
| </li></ul> |
| |
| <p>GCC support of fixed-point types as specified by the draft technical report |
| is incomplete: |
| </p> |
| <ul> |
| <li> Pragmas to control overflow and rounding behaviors are not implemented. |
| </li></ul> |
| |
| <p>Fixed-point types are supported by the DWARF 2 debug information format. |
| </p> |
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