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Re: Why sizeof(main) = 1?

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On 9/2/2013 5:07 AM, kzelechowski@e3tech.local wrote:
> (sizeof main == 1) because (main) is treated as a logical value.  Compare: {
> if (main) yadda; }

No, it is 1 because gcc has decided that, as an extension to the C standard, 
it will allow sizeof to be applied to functions, and will be the value 1.

6.5.3.4p1 states:

     "The sizeof operator shall not be applied to an expression that has
     function type or an incomplete type, to the parenthesized name of
     such a type, or to an expression that designates a bit-field member."

I believe that the name of a function is an "expression that has function 
type".  (Though I'm sure I will be quickly corrected if I am mistaken.)

If I try compiling the following code:

====
extern void foo(void);
int x = (int)sizeof foo;
====

I get the error:

     'void (__cdecl *)(void)': illegal sizeof operand

>
> Użytkownik "Myth__Buster"  napisał w wiadomości grup
> dyskusyjnych:clcm-20130104-0002@plethora.net...
>
> Hi,
>
> On a Linux system with gcc, I am just wondering why sizeof(main) can
> be 1 or sizeof when applied on any function name can yield 1 ever? Or
> is it only gcc's perspective to say sizeof of an implicit function
> pointer to be 1 since it gives sizeof(void) to be 1 based on the
> backward compatibility with the pre C99 notion that void* had its
> predecessor char* and usually sizeof(char) being 1?
>
> Also, I tried the invariably buggy code to see if at all sizeof(main)
> = 1 can be realized.
-- 
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Thread

Why sizeof(main) = 1? Myth__Buster <raghavanil4m@gmail.com> - 2013-01-04 18:14 -0600
  Re: Why sizeof(main) = 1? Barry Schwarz <schwarzb@dqel.com> - 2013-02-26 10:51 -0600
    Re: Why sizeof(main) = 1? Keith Thompson <kst-u@mib.org> - 2013-03-11 18:25 -0500
  Re: Why sizeof(main) = 1? Jasen Betts <jasen@xnet.co.nz> - 2013-02-26 10:51 -0600
  Re: Why sizeof(main) = 1? gordonb.k8xjg@burditt.org (Gordon Burditt) - 2013-02-26 10:51 -0600
  Re: Why sizeof(main) = 1? <kzelechowski@e3tech.local> - 2013-09-02 04:07 -0500
    Re: Why sizeof(main) = 1? James Kuyper <jameskuyper@verizon.net> - 2013-09-06 23:25 -0500
      Re: Why sizeof(main) = 1? Keith Thompson <kst-u@mib.org> - 2013-09-11 17:26 -0500
        Re: Why sizeof(main) = 1? James Kuyper <jameskuyper@verizon.net> - 2013-09-12 11:29 -0500
    Re: Why sizeof(main) = 1? Keith Thompson <kst-u@mib.org> - 2013-09-06 23:25 -0500
      Re: Why sizeof(main) = 1? Robert Wessel <robertwessel2@yahoo.com> - 2013-09-11 17:27 -0500
        Re: Why sizeof(main) = 1? James Kuyper <jameskuyper@verizon.net> - 2013-09-12 11:29 -0500
        Re: Why sizeof(main) = 1? Keith Thompson <kst-u@mib.org> - 2013-09-12 11:30 -0500
    Re: Why sizeof(main) = 1? Ken Brody <kenbrody@spamcop.net> - 2013-09-06 23:25 -0500

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