1<html lang="en"> 2<head> 3<title>Long Long - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> 9<link rel="prev" href="Conditionals.html#Conditionals" title="Conditionals"> 10<link rel="next" href="_005f_005fint128.html#g_t_005f_005fint128" title="__int128"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). A copy of the license is included in the section entitled 23``GNU Free Documentation License''. 24 25(a) The FSF's Front-Cover Text is: 26 27 A GNU Manual 28 29(b) The FSF's Back-Cover Text is: 30 31 You have freedom to copy and modify this GNU Manual, like GNU 32 software. Copies published by the Free Software Foundation raise 33 funds for GNU development.--> 34<meta http-equiv="Content-Style-Type" content="text/css"> 35<style type="text/css"><!-- 36 pre.display { font-family:inherit } 37 pre.format { font-family:inherit } 38 pre.smalldisplay { font-family:inherit; font-size:smaller } 39 pre.smallformat { font-family:inherit; font-size:smaller } 40 pre.smallexample { font-size:smaller } 41 pre.smalllisp { font-size:smaller } 42 span.sc { font-variant:small-caps } 43 span.roman { font-family:serif; font-weight:normal; } 44 span.sansserif { font-family:sans-serif; font-weight:normal; } 45--></style> 46<link rel="stylesheet" type="text/css" href="../cs.css"> 47</head> 48<body> 49<div class="node"> 50<a name="Long-Long"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="_005f_005fint128.html#g_t_005f_005fint128">__int128</a>, 53Previous: <a rel="previous" accesskey="p" href="Conditionals.html#Conditionals">Conditionals</a>, 54Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> 55<hr> 56</div> 57 58<h3 class="section">6.9 Double-Word Integers</h3> 59 60<p><a name="index-g_t_0040code_007blong-long_007d-data-types-2276"></a><a name="index-double_002dword-arithmetic-2277"></a><a name="index-multiprecision-arithmetic-2278"></a><a name="index-g_t_0040code_007bLL_007d-integer-suffix-2279"></a><a name="index-g_t_0040code_007bULL_007d-integer-suffix-2280"></a> 61ISO C99 supports data types for integers that are at least 64 bits wide, 62and as an extension GCC supports them in C90 mode and in C++. 63Simply write <code>long long int</code> for a signed integer, or 64<code>unsigned long long int</code> for an unsigned integer. To make an 65integer constant of type <code>long long int</code>, add the suffix ‘<samp><span class="samp">LL</span></samp>’ 66to the integer. To make an integer constant of type <code>unsigned long 67long int</code>, add the suffix ‘<samp><span class="samp">ULL</span></samp>’ to the integer. 68 69 <p>You can use these types in arithmetic like any other integer types. 70Addition, subtraction, and bitwise boolean operations on these types 71are open-coded on all types of machines. Multiplication is open-coded 72if the machine supports fullword-to-doubleword a widening multiply 73instruction. Division and shifts are open-coded only on machines that 74provide special support. The operations that are not open-coded use 75special library routines that come with GCC. 76 77 <p>There may be pitfalls when you use <code>long long</code> types for function 78arguments, unless you declare function prototypes. If a function 79expects type <code>int</code> for its argument, and you pass a value of type 80<code>long long int</code>, confusion will result because the caller and the 81subroutine will disagree about the number of bytes for the argument. 82Likewise, if the function expects <code>long long int</code> and you pass 83<code>int</code>. The best way to avoid such problems is to use prototypes. 84 85 </body></html> 86 87