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Fixed_002dPoint.html

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  24. <title>Using the GNU Compiler Collection (GCC): Fixed-Point</title>
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    71. 

  71. <a name="Fixed_002dPoint"></a>
    72. 

  72. <div class="header">
    73. 

  73. <p>
    74. 

  74. 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> &nbsp; [<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>
    75. 

  75. </div>
    76. 

  76. <hr>
    77. 

  77. <a name="Fixed_002dPoint-Types"></a>
    78. 

  78. <h3 class="section">6.15 Fixed-Point Types</h3>
    79. 

  79. <a name="index-fixed_002dpoint-types"></a>
    80. 

  80. <a name="index-_005fFract-data-type"></a>
    81. 

  81. <a name="index-_005fAccum-data-type"></a>
    82. 

  82. <a name="index-_005fSat-data-type"></a>
    83. 

  83. <a name="index-hr-fixed_002dsuffix"></a>
    84. 

  84. <a name="index-r-fixed_002dsuffix"></a>
    85. 

  85. <a name="index-lr-fixed_002dsuffix"></a>
    86. 

  86. <a name="index-llr-fixed_002dsuffix"></a>
    87. 

  87. <a name="index-uhr-fixed_002dsuffix"></a>
    88. 

  88. <a name="index-ur-fixed_002dsuffix"></a>
    89. 

  89. <a name="index-ulr-fixed_002dsuffix"></a>
    90. 

  90. <a name="index-ullr-fixed_002dsuffix"></a>
    91. 

  91. <a name="index-hk-fixed_002dsuffix"></a>
    92. 

  92. <a name="index-k-fixed_002dsuffix"></a>
    93. 

  93. <a name="index-lk-fixed_002dsuffix"></a>
    94. 

  94. <a name="index-llk-fixed_002dsuffix"></a>
    95. 

  95. <a name="index-uhk-fixed_002dsuffix"></a>
    96. 

  96. <a name="index-uk-fixed_002dsuffix"></a>
    97. 

  97. <a name="index-ulk-fixed_002dsuffix"></a>
    98. 

  98. <a name="index-ullk-fixed_002dsuffix"></a>
    99. 

  99. <a name="index-HR-fixed_002dsuffix"></a>
    100. 

  100. <a name="index-R-fixed_002dsuffix"></a>
    101. 

  101. <a name="index-LR-fixed_002dsuffix"></a>
    102. 

  102. <a name="index-LLR-fixed_002dsuffix"></a>
    103. 

  103. <a name="index-UHR-fixed_002dsuffix"></a>
    104. 

  104. <a name="index-UR-fixed_002dsuffix"></a>
    105. 

  105. <a name="index-ULR-fixed_002dsuffix"></a>
    106. 

  106. <a name="index-ULLR-fixed_002dsuffix"></a>
    107. 

  107. <a name="index-HK-fixed_002dsuffix"></a>
    108. 

  108. <a name="index-K-fixed_002dsuffix"></a>
    109. 

  109. <a name="index-LK-fixed_002dsuffix"></a>
    110. 

  110. <a name="index-LLK-fixed_002dsuffix"></a>
    111. 

  111. <a name="index-UHK-fixed_002dsuffix"></a>
    112. 

  112. <a name="index-UK-fixed_002dsuffix"></a>
    113. 

  113. <a name="index-ULK-fixed_002dsuffix"></a>
    114. 

  114. <a name="index-ULLK-fixed_002dsuffix"></a>
    115. 

  115. 

  116. <p>As an extension, GNU C supports fixed-point types as
    117. 

  117. defined in the N1169 draft of ISO/IEC DTR 18037.  Support for fixed-point
    118. 

  118. types in GCC will evolve as the draft technical report changes.
    119. 

  119. Calling conventions for any target might also change.  Not all targets
    120. 

  120. support fixed-point types.
    121. 

  121. </p>
    122. 

  122. <p>The fixed-point types are
    123. 

  123. <code>short _Fract</code>,
    124. 

  124. <code>_Fract</code>,
    125. 

  125. <code>long _Fract</code>,
    126. 

  126. <code>long long _Fract</code>,
    127. 

  127. <code>unsigned short _Fract</code>,
    128. 

  128. <code>unsigned _Fract</code>,
    129. 

  129. <code>unsigned long _Fract</code>,
    130. 

  130. <code>unsigned long long _Fract</code>,
    131. 

  131. <code>_Sat short _Fract</code>,
    132. 

  132. <code>_Sat _Fract</code>,
    133. 

  133. <code>_Sat long _Fract</code>,
    134. 

  134. <code>_Sat long long _Fract</code>,
    135. 

  135. <code>_Sat unsigned short _Fract</code>,
    136. 

  136. <code>_Sat unsigned _Fract</code>,
    137. 

  137. <code>_Sat unsigned long _Fract</code>,
    138. 

  138. <code>_Sat unsigned long long _Fract</code>,
    139. 

  139. <code>short _Accum</code>,
    140. 

  140. <code>_Accum</code>,
    141. 

  141. <code>long _Accum</code>,
    142. 

  142. <code>long long _Accum</code>,
    143. 

  143. <code>unsigned short _Accum</code>,
    144. 

  144. <code>unsigned _Accum</code>,
    145. 

  145. <code>unsigned long _Accum</code>,
    146. 

  146. <code>unsigned long long _Accum</code>,
    147. 

  147. <code>_Sat short _Accum</code>,
    148. 

  148. <code>_Sat _Accum</code>,
    149. 

  149. <code>_Sat long _Accum</code>,
    150. 

  150. <code>_Sat long long _Accum</code>,
    151. 

  151. <code>_Sat unsigned short _Accum</code>,
    152. 

  152. <code>_Sat unsigned _Accum</code>,
    153. 

  153. <code>_Sat unsigned long _Accum</code>,
    154. 

  154. <code>_Sat unsigned long long _Accum</code>.
    155. 

  155. </p>
    156. 

  156. <p>Fixed-point data values contain fractional and optional integral parts.
    157. 

  157. The format of fixed-point data varies and depends on the target machine.
    158. 

  158. </p>
    159. 

  159. <p>Support for fixed-point types includes:
    160. 

  160. </p><ul>
    161. 

  161. <li> prefix and postfix increment and decrement operators (<code>++</code>, <code>--</code>)
    162. 

  162. </li><li> unary arithmetic operators (<code>+</code>, <code>-</code>, <code>!</code>)
    163. 

  163. </li><li> binary arithmetic operators (<code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>)
    164. 

  164. </li><li> binary shift operators (<code>&lt;&lt;</code>, <code>&gt;&gt;</code>)
    165. 

  165. </li><li> relational operators (<code>&lt;</code>, <code>&lt;=</code>, <code>&gt;=</code>, <code>&gt;</code>)
    166. 

  166. </li><li> equality operators (<code>==</code>, <code>!=</code>)
    167. 

  167. </li><li> assignment operators (<code>+=</code>, <code>-=</code>, <code>*=</code>, <code>/=</code>,
    168. 

  168. <code>&lt;&lt;=</code>, <code>&gt;&gt;=</code>)
    169. 

  169. </li><li> conversions to and from integer, floating-point, or fixed-point types
    170. 

  170. </li></ul>
    171. 

  171. 

  172. <p>Use a suffix in a fixed-point literal constant:
    173. 

  173. </p><ul>
    174. 

  174. <li> &lsquo;<samp>hr</samp>&rsquo; or &lsquo;<samp>HR</samp>&rsquo; for <code>short _Fract</code> and
    175. 

  175. <code>_Sat short _Fract</code>
    176. 

  176. </li><li> &lsquo;<samp>r</samp>&rsquo; or &lsquo;<samp>R</samp>&rsquo; for <code>_Fract</code> and <code>_Sat _Fract</code>
    177. 

  177. </li><li> &lsquo;<samp>lr</samp>&rsquo; or &lsquo;<samp>LR</samp>&rsquo; for <code>long _Fract</code> and
    178. 

  178. <code>_Sat long _Fract</code>
    179. 

  179. </li><li> &lsquo;<samp>llr</samp>&rsquo; or &lsquo;<samp>LLR</samp>&rsquo; for <code>long long _Fract</code> and
    180. 

  180. <code>_Sat long long _Fract</code>
    181. 

  181. </li><li> &lsquo;<samp>uhr</samp>&rsquo; or &lsquo;<samp>UHR</samp>&rsquo; for <code>unsigned short _Fract</code> and
    182. 

  182. <code>_Sat unsigned short _Fract</code>
    183. 

  183. </li><li> &lsquo;<samp>ur</samp>&rsquo; or &lsquo;<samp>UR</samp>&rsquo; for <code>unsigned _Fract</code> and
    184. 

  184. <code>_Sat unsigned _Fract</code>
    185. 

  185. </li><li> &lsquo;<samp>ulr</samp>&rsquo; or &lsquo;<samp>ULR</samp>&rsquo; for <code>unsigned long _Fract</code> and
    186. 

  186. <code>_Sat unsigned long _Fract</code>
    187. 

  187. </li><li> &lsquo;<samp>ullr</samp>&rsquo; or &lsquo;<samp>ULLR</samp>&rsquo; for <code>unsigned long long _Fract</code>
    188. 

  188. and <code>_Sat unsigned long long _Fract</code>
    189. 

  189. </li><li> &lsquo;<samp>hk</samp>&rsquo; or &lsquo;<samp>HK</samp>&rsquo; for <code>short _Accum</code> and
    190. 

  190. <code>_Sat short _Accum</code>
    191. 

  191. </li><li> &lsquo;<samp>k</samp>&rsquo; or &lsquo;<samp>K</samp>&rsquo; for <code>_Accum</code> and <code>_Sat _Accum</code>
    192. 

  192. </li><li> &lsquo;<samp>lk</samp>&rsquo; or &lsquo;<samp>LK</samp>&rsquo; for <code>long _Accum</code> and
    193. 

  193. <code>_Sat long _Accum</code>
    194. 

  194. </li><li> &lsquo;<samp>llk</samp>&rsquo; or &lsquo;<samp>LLK</samp>&rsquo; for <code>long long _Accum</code> and
    195. 

  195. <code>_Sat long long _Accum</code>
    196. 

  196. </li><li> &lsquo;<samp>uhk</samp>&rsquo; or &lsquo;<samp>UHK</samp>&rsquo; for <code>unsigned short _Accum</code> and
    197. 

  197. <code>_Sat unsigned short _Accum</code>
    198. 

  198. </li><li> &lsquo;<samp>uk</samp>&rsquo; or &lsquo;<samp>UK</samp>&rsquo; for <code>unsigned _Accum</code> and
    199. 

  199. <code>_Sat unsigned _Accum</code>
    200. 

  200. </li><li> &lsquo;<samp>ulk</samp>&rsquo; or &lsquo;<samp>ULK</samp>&rsquo; for <code>unsigned long _Accum</code> and
    201. 

  201. <code>_Sat unsigned long _Accum</code>
    202. 

  202. </li><li> &lsquo;<samp>ullk</samp>&rsquo; or &lsquo;<samp>ULLK</samp>&rsquo; for <code>unsigned long long _Accum</code>
    203. 

  203. and <code>_Sat unsigned long long _Accum</code>
    204. 

  204. </li></ul>
    205. 

  205. 

  206. <p>GCC support of fixed-point types as specified by the draft technical report
    207. 

  207. is incomplete:
    208. 

  208. </p>
    209. 

  209. <ul>
    210. 

  210. <li> Pragmas to control overflow and rounding behaviors are not implemented.
    211. 

  211. </li></ul>
    212. 

  212. 

  213. <p>Fixed-point types are supported by the DWARF debug information format.
    214. 

  214. </p>
    215. 

  215. <hr>
    216. 

  216. <div class="header">
    217. 

  217. <p>
    218. 

  218. 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> &nbsp; [<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>
    219. 

  219. </div>
    220. 

  220. 

  221. 

  222. 

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    224. 

  224. </html>
    225.