<html lang="en">
<head>
<title>Long Long - Using the GNU Compiler Collection (GCC)</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions">
<link rel="prev" href="Conditionals.html#Conditionals" title="Conditionals">
<link rel="next" href="Complex.html#Complex" title="Complex">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
2008 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Funding Free Software'', the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below).  A copy of the license is included in the section entitled
``GNU Free Documentation License''.

(a) The FSF's Front-Cover Text is:

     A GNU Manual

(b) The FSF's Back-Cover Text is:

     You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development.-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
  pre.display { font-family:inherit }
  pre.format  { font-family:inherit }
  pre.smalldisplay { font-family:inherit; font-size:smaller }
  pre.smallformat  { font-family:inherit; font-size:smaller }
  pre.smallexample { font-size:smaller }
  pre.smalllisp    { font-size:smaller }
  span.sc    { font-variant:small-caps }
  span.roman { font-family:serif; font-weight:normal; } 
  span.sansserif { font-family:sans-serif; font-weight:normal; } 
--></style>
<link rel="stylesheet" type="text/css" href="../cs.css">
</head>
<body>
<div class="node">
<a name="Long-Long"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="Complex.html#Complex">Complex</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Conditionals.html#Conditionals">Conditionals</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a>
<hr>
</div>

<h3 class="section">6.8 Double-Word Integers</h3>

<p><a name="index-g_t_0040code_007blong-long_007d-data-types-2216"></a><a name="index-double_002dword-arithmetic-2217"></a><a name="index-multiprecision-arithmetic-2218"></a><a name="index-g_t_0040code_007bLL_007d-integer-suffix-2219"></a><a name="index-g_t_0040code_007bULL_007d-integer-suffix-2220"></a>
ISO C99 supports data types for integers that are at least 64 bits wide,
and as an extension GCC supports them in C90 mode and in C++. 
Simply write <code>long long int</code> for a signed integer, or
<code>unsigned long long int</code> for an unsigned integer.  To make an
integer constant of type <code>long long int</code>, add the suffix &lsquo;<samp><span class="samp">LL</span></samp>&rsquo;
to the integer.  To make an integer constant of type <code>unsigned long
long int</code>, add the suffix &lsquo;<samp><span class="samp">ULL</span></samp>&rsquo; to the integer.

 <p>You can use these types in arithmetic like any other integer types. 
Addition, subtraction, and bitwise boolean operations on these types
are open-coded on all types of machines.  Multiplication is open-coded
if the machine supports fullword-to-doubleword a widening multiply
instruction.  Division and shifts are open-coded only on machines that
provide special support.  The operations that are not open-coded use
special library routines that come with GCC.

 <p>There may be pitfalls when you use <code>long long</code> types for function
arguments, unless you declare function prototypes.  If a function
expects type <code>int</code> for its argument, and you pass a value of type
<code>long long int</code>, confusion will result because the caller and the
subroutine will disagree about the number of bytes for the argument. 
Likewise, if the function expects <code>long long int</code> and you pass
<code>int</code>.  The best way to avoid such problems is to use prototypes.

 </body></html>