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113 lines
5.1 KiB
HTML
113 lines
5.1 KiB
HTML
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<head>
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<title>Long Long (Using the GNU Compiler Collection (GCC))</title>
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<meta name="description" content="Long Long (Using the GNU Compiler Collection (GCC))">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="C-Extensions.html#C-Extensions" rel="up" title="C Extensions">
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<link href="Complex.html#Complex" rel="next" title="Complex">
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<link href="_005f_005fint128.html#g_t_005f_005fint128" rel="prev" title="__int128">
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<a name="Long-Long"></a>
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<div class="header">
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<p>
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Next: <a href="Complex.html#Complex" accesskey="n" rel="next">Complex</a>, Previous: <a href="_005f_005fint128.html#g_t_005f_005fint128" accesskey="p" rel="prev">__int128</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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</div>
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<hr>
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<a name="Double_002dWord-Integers"></a>
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<h3 class="section">6.9 Double-Word Integers</h3>
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<a name="index-long-long-data-types"></a>
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<a name="index-double_002dword-arithmetic"></a>
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<a name="index-multiprecision-arithmetic"></a>
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<a name="index-LL-integer-suffix"></a>
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<a name="index-ULL-integer-suffix"></a>
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<p>ISO C99 supports data types for integers that are at least 64 bits wide,
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and as an extension GCC supports them in C90 mode and in C++.
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Simply write <code>long long int</code> for a signed integer, or
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<code>unsigned long long int</code> for an unsigned integer. To make an
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integer constant of type <code>long long int</code>, add the suffix ‘<samp>LL</samp>’
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to the integer. To make an integer constant of type <code>unsigned long
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long int</code>, add the suffix ‘<samp>ULL</samp>’ to the integer.
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</p>
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<p>You can use these types in arithmetic like any other integer types.
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Addition, subtraction, and bitwise boolean operations on these types
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are open-coded on all types of machines. Multiplication is open-coded
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if the machine supports a fullword-to-doubleword widening multiply
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instruction. Division and shifts are open-coded only on machines that
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provide special support. The operations that are not open-coded use
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special library routines that come with GCC.
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</p>
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<p>There may be pitfalls when you use <code>long long</code> types for function
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arguments without function prototypes. If a function
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expects type <code>int</code> for its argument, and you pass a value of type
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<code>long long int</code>, confusion results because the caller and the
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subroutine disagree about the number of bytes for the argument.
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Likewise, if the function expects <code>long long int</code> and you pass
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<code>int</code>. The best way to avoid such problems is to use prototypes.
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</p>
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