From: "Mihai Donțu" <mihai.dontu@gmail.com>
To: Brian Dessent <brian@dessent.net>
Cc: gcc-help@gcc.gnu.org
Subject: Re: sizeof( function )
Date: Tue, 12 Jun 2007 17:05:00 -0000 [thread overview]
Message-ID: <200706121938.26865.mihai.dontu@gmail.com> (raw)
In-Reply-To: <466EC9C6.A5DF578A@dessent.net>
On Tuesday 12 June 2007 19:28, Brian Dessent wrote:
> Mihai Don?u wrote:
>
> > Not that is of great importance, but does anyone know why
> >
> > int main( void )
> > {
> > return printf( "%d\n", ( int )sizeof( main ) );
> > }
> >
> > prints 1 ? :)
> >
> > (sizeof( &main ) prints 4/8 as it should)
>
> In this context 'main' is a function type, i.e. a type that describes a
> function of a given return type and a given number and type of arguments
> (C99 §6.2.5 para. 20). It is invalid to use sizeof() with a function
> type expression (C99 §6.5.3.4 para. 1) and hence this code invokes
> undefined behavior. gcc gives a warning if you compile with -pedantic,
> but otherwise it apparently just returns 1; it would be equally within
> its rights to return 42 or to generate code to format the users hard
> drive -- that is the nature of undefined behavior.
Unlike me, you really do know your C99 book :)
Thanks a lot!
--
Mihai DonÈu
next prev parent reply other threads:[~2007-06-12 16:38 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-12 16:12 Mihai Donțu
2007-06-12 16:38 ` Brian Dessent
2007-06-12 16:56 ` Segher Boessenkool
2007-06-12 17:05 ` Mihai Donțu [this message]
2007-06-12 17:57 ` Ian Lance Taylor
2007-06-14 12:44 ` Martin Krischik
2007-06-12 17:18 Nick Maclaren
2007-06-12 17:27 ` Brian Dessent
2007-06-12 17:47 ` Segher Boessenkool
2007-06-12 21:55 Nick Maclaren
2007-06-14 13:14 Nick Maclaren
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