RealView Compilation Tools Compiler Reference Guide - ARM ...

C and C++ Implementation Details
• No locale is used to convert multibyte characters into the corresponding wide
characters for a wide character constant. This is not relevant to the generic
implementation.
5.1.2 Basic data types
This section describes how the basic data types are implemented in ARM C and C++.
Size and alignment of basic data types
Table 5-2 gives the size and natural alignment of the basic data types.
Table 5-2 Size and alignment of data types
Type Size in bits Natural alignment in bytes
char 8 1 (byte-aligned)
short 16 2 (halfword-aligned)
int 32 4 (word-aligned)
long 32 4 (word-aligned)
long long 64 8 (doubleword-aligned)
float 32 4 (word-aligned)
double 64 8 (doubleword-aligned)
long double 64 8 (doubleword-aligned)
All pointers 32 4 (word-aligned)
bool (C++ only) 8 1 (byte-aligned)
_Bool (C only a )
8 1 (byte-aligned)
wchar_t (C++ only) 16 2 (halfword-aligned)
a. stdbool.h can be used to define the bool macro in C.
Type alignment varies according to the context:
• Local variables are usually kept in registers, but when local variables spill onto
the stack, they are always word-aligned. For example, a spilled local char variable
has an alignment of 4.
• The natural alignment of a packed type is 1.
5-4 Copyright © 2007, 2010 ARM Limited. All rights reserved. ARM DUI 0348A
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