114 lines
5.2 KiB
HTML
114 lines
5.2 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Using the GNU Compiler Collection (GCC): Long Long</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): Long Long">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Long Long">
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<meta name="resource-type" content="document">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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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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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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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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</body>
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</html>
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