From: "Martin Krischik" <krischik@users.sourceforge.net>
To: gcc-help@gcc.gnu.org
Subject: Re: sizeof( function )
Date: Thu, 14 Jun 2007 12:44:00 -0000 [thread overview]
Message-ID: <op.ttwqf2ohz25lew@super> (raw)
In-Reply-To: <466EC9C6.A5DF578A@dessent.net>
Am 12.06.2007, 19:28 Uhr, schrieb Brian Dessent <brian@dessent.net>:
> 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.
If it is invalid to use sizeof() with a function type expression - why not
an make it an compile time error?
Martin
next prev parent reply other threads:[~2007-06-14 10:37 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
2007-06-12 17:57 ` Ian Lance Taylor
2007-06-14 12:44 ` Martin Krischik [this message]
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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