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core/com.nokia.carbide.cpp.compiler.doc.user/html/c_compiler/c_typeof_operator.htm
author timkelly
Thu, 10 Dec 2009 13:45:47 -0600
branchRCL_2_4
changeset 671 80524b72f957
parent 0 fb279309251b
child 1641 2b3996fc09a1
permissions -rw-r--r--
Add S60 5.2 support.
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<title>The __typeof__() and typeof() operators</title>
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<h3> The __typeof__() and typeof() operators</h3>
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<p>  With the <span class="code">__typeof__()</span> operator, the compiler lets you specify the data type of an expression. Listing 1 shows an example.</p>
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<p class="listing">__typeof__(<em>expression</em>)</p>
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<p>where expression is any valid C expression or data type. Because the compiler translates a <span class="code">__typeof__()</span> expression into a data type, you can use this expression wherever a normal type would be specified.</p>
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<p>Like the <span class="code">sizeof()</span> operator, <span class="code">__typeof__()</span> is only evaluated at compile time, not at runtime. For related information, see &ldquo;Sizeof() Operator Data Type&rdquo;.</p>
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<p>If you enable the gcc_extensions pragma, the <span class="code">typeof()</span> operator is equivalent to the <span class="code">__typeof__()</span> operator.</p>
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<div class="listing">
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  <h4>Listing 1. Example of __typeof__() and typeof() Operators</h4>
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  <p>char *cp;<br />
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    int *ip;<br />
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    long *lp;</p>
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  <p>__typeof__(*ip) i; /* equivalent to &quot;int i;&quot; */<br />
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    __typeof__(*lp) l; /* equivalent to &quot;long l;&quot; */</p>
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  <p>#pragma gcc_extensions on<br />
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    typeof(*cp) c; /* equivalent to &quot;char c;&quot; */<br />
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  </p>
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</div>
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<div id="footer">Copyright &copy; 2009 Nokia Corporation and/or its subsidiary(-ies). All rights reserved. <br>License: <a href="http://www.eclipse.org/legal/epl-v10.html">http://www.eclipse.org/legal/epl-v10.html</a></div>
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FCL/sftools/dev/ide/carbidecpp