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Revision 1.2, Sun Dec 19 08:10:09 2010 UTC (13 years, 4 months ago) by jruoho
Branch: MAIN
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Changes since 1.1: +3 -2 lines 

Document the __alignof__ GNU extension.

.\" $NetBSD: typeof.3,v 1.2 2010/12/19 08:10:09 jruoho Exp $
.\"
.\" Copyright (c) 2010 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd December 19, 2010
.Dt TYPEOF 3
.Os
.Sh NAME
.Nm typeof
.Nd GNU extension for type of an expression
.Sh SYNOPSIS
.Ft type
.Fn typeof "expression"
.Sh DESCRIPTION
The
.Fn typeof
construct can be used to obtain the type of an expression.
The syntax is comparable to that of
.Fn sizeof ,
but semantically
.Fn typeof
operates like a type name defined with
.Em typedef .
.Sh EXAMPLES
The following is a typical example of a type-generic macro:
.Bd -literal -offset indent
#define MAX(a, b) ({		\\
	typeof(a) _a = (a);	\\
	typeof(b) _b = (b);	\\
	_a > _b ? _a : _b;	\\
})
.Ed
.Sh SEE ALSO
.Xr gcc 1 ,
.Xr __alignof__ 3 ,
.Xr attribute 3 ,
.Xr offsetof 3
.Sh CAVEATS
The
.Fn typeof
construct is a non-standard, compiler-specific extension.