Re: (part 21) Han from China answers your C questions

[Lew Pitcher]

On November 14, 2008 15:00, in comp.lang.c, Nomen Nescio (nobody@dizum.c om)
wrote:

its urgent.pls help me.
>
mona said:

>hi,i urgently need a project including graphics,pointe rs.

[snip]

In the meantime, here's a program that meets the specifications:
>
#include <stdio.h>
>
int
main(void)
{
/*
* What we have here is a simple graphics output.
* We satisfy the requirement for pointers in two ways:
* (1) we have a graphics pointer (or arrow)
* (2) the argument to printf() decays to a pointer
*/
printf(" === \n");

Overkill

return 0;
}

Try

#include <stdio.h>

int main(void)
{
puts(" --- ")
return 0;
}

--
Lew Pitcher

Master Codewright & JOAT-in-training | Registered Linux User #112576
http://pitcher.digitalfreehold.ca/ | GPG public key available by request
---------- Slackware - Because I know what I'm doing. ------

[Andrey Tarasevich]

Re: (part 21) Han from China answers your C questions

Lew Pitcher wrote:

>
#include <stdio.h>
>
int main(void)
{
puts(" --- ")
return 0;
}
>

Overkill

#include <stdio.h>

int main(void) {
puts(" --")
}

--
Best regards,
Andrey Tarasevich

[Lew Pitcher]

Re: (part 21) Han from China answers your C questions

On November 14, 2008 15:11, in comp.lang.c, Lew Pitcher
(lpitcher@teksa vvy.com) wrote:

[snip]

>
#include <stdio.h>
>
int main(void)
{
puts(" --- ")

gaak! I missed a semicolon here.

return 0;
}
>

I promise to be more carefull next time

--
Lew Pitcher

Master Codewright & JOAT-in-training | Registered Linux User #112576
http://pitcher.digitalfreehold.ca/ | GPG public key available by request
---------- Slackware - Because I know what I'm doing. ------

[s0suk3@gmail.com]

Re: (part 21) Han from China answers your C questions

On Nov 14, 3:28 pm, Andrey Tarasevich <andreytarasevi ch@hotmail.com>
wrote:

Lew Pitcher wrote:
>

  #include <stdio.h>

>

  int main(void)
  {
    puts("  --- ")
    return 0;
  }

>
Overkill
>
   #include <stdio.h>
>
   int main(void) {
     puts(" --")
   }

Overkill. The #include line will bring in a bunch of stuff :-)

int main(void) { int puts(const char *); puts(" --"); }

Sebastian

[Ralf Damaschke]

Re: (part 21) Han from China answers your C questions

s0suk3 wrote:

On Nov 14, 3:28 pm, Andrey Tarasevich <andreytarasevi ch@hotmail.com>
wrote:

>Lew Pitcher wrote:
>>

  #include <stdio.h>

>>

  int main(void)
  {
    puts("  --- ")
    return 0;
  }

>>
>Overkill
>>
>   #include <stdio.h>
>>
>   int main(void) {
>     puts(" --")
>   }

>
Overkill. The #include line will bring in a bunch of stuff :-)
>
int main(void) { int puts(const char *); puts(" --"); }

Overkill. No need for a prototype (even in C99).

int main(void) { int puts(); puts(" --"); }

-- Ralf

[Richard Heathfield]

Re: (part 21) Han from China answers your C questions

Ralf Damaschke said:

s0suk3 wrote:
>

>On Nov 14, 3:28 pm, Andrey Tarasevich <andreytarasevi ch@hotmail.com>
>wrote:

>>Lew Pitcher wrote:
>>>
>#include <stdio.h>
>>>
>int main(void)
>{
>puts(" --- ")
>return 0;
>}
>>>
>>Overkill
>>>
>>#include <stdio.h>
>>>
>>int main(void) {
>>puts(" --")
>>}

>>
>Overkill. The #include line will bring in a bunch of stuff :-)
>>
>int main(void) { int puts(const char *); puts(" --"); }

>
Overkill. No need for a prototype (even in C99).
>
int main(void) { int puts(); puts(" --"); }

Overkill. No need for a prototype (even in C99).

int main() { int puts(); puts(" --"; }

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Harald van =?UTF-8?b?RMSzaw==?=]

Re: (part 21) Han from China answers your C questions

On Sat, 15 Nov 2008 07:59:35 +0000, Ralf Damaschke wrote:

s0suk3 wrote:

>Overkill. The #include line will bring in a bunch of stuff :-)
>>
>int main(void) { int puts(const char *); puts(" --"); }

>
Overkill. No need for a prototype (even in C99).
>
int main(void) { int puts(); puts(" --"); }

This doesn't convert the pointer to the string from char * to const char
*. I doubt any implementation will even notice, but you need either the
prototype, or you need to change the call to puts((const char *) " --");
for it to be valid.

[Flash Gordon]

Re: (part 21) Han from China answers your C questions

Harald van Dijk wrote, On 15/11/08 10:04:

On Sat, 15 Nov 2008 07:59:35 +0000, Ralf Damaschke wrote:

>s0suk3 wrote:

>>Overkill. The #include line will bring in a bunch of stuff :-)
>>>
>>int main(void) { int puts(const char *); puts(" --"); }

>Overkill. No need for a prototype (even in C99).
>>
>int main(void) { int puts(); puts(" --"); }

>
This doesn't convert the pointer to the string from char * to const char
*. I doubt any implementation will even notice, but you need either the
prototype, or you need to change the call to puts((const char *) " --");
for it to be valid.

There are other ways, such as using a variable, and the spaces are
overkill...

int main(void){int puts();const char*s=" --";puts(s);}
int main(void){int puts();puts((co nst char*)" --");}
--
Flash Gordon
If spamming me sent it to smap@spam.cause way.com
If emailing me use my reply-to address
See the comp.lang.c Wiki hosted by me at http://clc-wiki.net/

[pete]

Re: (part 21) Han from China answers your C questions

Richard Heathfield wrote:

Ralf Damaschke said:
>

>s0suk3 wrote:
>>

>>On Nov 14, 3:28 pm, Andrey Tarasevich <andreytarasevi ch@hotmail.com>
>>wrote:
>>>Lew Pitcher wrote:
>>>>
>>>>#include <stdio.h>
>>>>int main(void)
>>>>{
>>>>puts(" --- ")
>>>>return 0;
>>>>}
>>>Overkill
>>>>
>>>#include <stdio.h>
>>>>
>>>int main(void) {
>>>puts(" --")
>>>}
>>Overkill. The #include line will bring in a bunch of stuff :-)
>>>
>>int main(void) { int puts(const char *); puts(" --"); }

>Overkill. No need for a prototype (even in C99).
>>
>int main(void) { int puts(); puts(" --"); }

>
Overkill. No need for a prototype (even in C99).
>
int main() { int puts(); puts(" --"; }

What do you mean by "(even in C99)" ?

There is no implicit function declaration in C99.
That's a C89 feature.

--
pete

[Harald van =?UTF-8?b?RMSzaw==?=]

Re: (part 21) Han from China answers your C questions

On Sat, 15 Nov 2008 07:35:48 -0500, pete wrote:

Richard Heathfield wrote:

>Ralf Damaschke said:

>>s0suk3 wrote:
>>>int main(void) { int puts(const char *); puts(" --"); }
>>Overkill. No need for a prototype (even in C99).
>>>
>>int main(void) { int puts(); puts(" --"); }

>>
>Overkill. No need for a prototype (even in C99).
>>
>int main() { int puts(); puts(" --"; }

>
What do you mean by "(even in C99)" ?
>
There is no implicit function declaration in C99. That's a C89 feature.

Yes, but unprototyped functions are allowed even in C99. Ralf Damaschke
removed "const char *" from the declaration of puts. Richard Heathfield
removed "void" from the definition of main. Both kept the one called
function explicitly declared. There is no implicit function declaration
here.

[Keith Thompson]

Re: (part 21) Han from China answers your C questions

Richard Heathfield <rjh@see.sig.in validwrites:

Ralf Damaschke said:

>s0suk3 wrote:

>>On Nov 14, 3:28 pm, Andrey Tarasevich <andreytarasevi ch@hotmail.com>
>>wrote:
>>>Lew Pitcher wrote:
>>>>
>>#include <stdio.h>
>>>>
>>int main(void)
>>{
>>puts(" --- ")
>>return 0;
>>}
>>>>
>>>Overkill
>>>>
>>>#include <stdio.h>
>>>>
>>>int main(void) {
>>>puts(" --")
>>>}
>>>
>>Overkill. The #include line will bring in a bunch of stuff :-)
>>>
>>int main(void) { int puts(const char *); puts(" --"); }

>>
>Overkill. No need for a prototype (even in C99).
>>
>int main(void) { int puts(); puts(" --"); }

>
Overkill. No need for a prototype (even in C99).
>
int main() { int puts(); puts(" --"; }

Actually, that's debatable -- and it's been debated here before.
The argument is that declaration "int main()" isn't equivalent to
"int main(void)", since the former permits (with undefined behavior)
"main(42)" while the latter makes it a constraint violation; see
C99 5.1.2.2.1.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Richard Heathfield]

Re: (part 21) Han from China answers your C questions

Keith Thompson said:

Richard Heathfield <rjh@see.sig.in validwrites:

>Ralf Damaschke said:

>>s0suk3 wrote:

<snip>

>>>int main(void) { int puts(const char *); puts(" --"); }
>>>
>>Overkill. No need for a prototype (even in C99).
>>>
>>int main(void) { int puts(); puts(" --"); }

>>
>Overkill. No need for a prototype (even in C99).
>>
>int main() { int puts(); puts(" --"; }

>
Actually, that's debatable -- and it's been debated here before.
The argument is that declaration "int main()" isn't equivalent to
"int main(void)", since the former permits (with undefined behavior)
"main(42)" while the latter makes it a constraint violation; see
C99 5.1.2.2.1.

Yes, but the above code doesn't *contain* main(42). If you simply meant
"it's better to use int main(void) than int main()", I agree. But that
wasn't the cake we were baking on this occasion.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Harald van =?UTF-8?b?RMSzaw==?=]

Re: (part 21) Han from China answers your C questions

On Sat, 15 Nov 2008 17:12:57 +0000, Richard Heathfield wrote:

Keith Thompson said:

>Richard Heathfield <rjh@see.sig.in validwrites:

>>Ralf Damaschke said:
>>>s0suk3 wrote:

<snip>

>>>>int main(void) { int puts(const char *); puts(" --"); }
>>>>
>>>Overkill. No need for a prototype (even in C99).
>>>>
>>>int main(void) { int puts(); puts(" --"); }
>>>
>>Overkill. No need for a prototype (even in C99).
>>>
>>int main() { int puts(); puts(" --"; }

>>
>Actually, that's debatable -- and it's been debated here before. The
>argument is that declaration "int main()" isn't equivalent to "int
>main(void)", since the former permits (with undefined behavior)
>"main(42)" while the latter makes it a constraint violation; see C99
>5.1.2.2.1.

>
Yes, but the above code doesn't *contain* main(42).

But if main() isn't equivalent to main(void), and main must be defined as
int main(void), int main(int argc, char *argv[]), or equivalent, then
defining it as main() is invalid, even if you don't call main(42). That's
the point I believe Keith Thompson was making.

(Personally, I believe int main() is valid.)

[Richard Heathfield]

Re: (part 21) Han from China answers your C questions

Harald van D?k said:

<snip>

But if main() isn't equivalent to main(void), and main must be defined as
int main(void), int main(int argc, char *argv[]), or equivalent, then
defining it as main() is invalid, even if you don't call main(42). That's
the point I believe Keith Thompson was making.

Oh, I see.

(Personally, I believe int main() is valid.)

I agree. Note that int main() - in a function *definition* - defines main
as taking no parameters. The relevant quote is in 3.5.4.3: "An empty list
in a function declarator that is part of a function definition specifies
that the function has no parameters. The empty list in a function
declarator that is not part of a function definition specifies that no
information about the number or types of the parameters is supplied."

Almost identical wording appears in 6.7.5.3(14) of C99. Incidentally, the
wording is slightly tighter in C99 - which is actually quite interesting,
because it reveals a slight flaw in the wording of the above, but the
differences aren't relevant to the current case.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Keith Thompson]

Re: (part 21) Han from China answers your C questions

Richard Heathfield <rjh@see.sig.in validwrites:

Harald van D?k said:
>
<snip>
>

>But if main() isn't equivalent to main(void), and main must be defined as
>int main(void), int main(int argc, char *argv[]), or equivalent, then
>defining it as main() is invalid, even if you don't call main(42). That's
>the point I believe Keith Thompson was making.

>
Oh, I see.
>

>(Personally, I believe int main() is valid.)

>
I agree. Note that int main() - in a function *definition* - defines main
as taking no parameters. The relevant quote is in 3.5.4.3: "An empty list
in a function declarator that is part of a function definition specifies
that the function has no parameters. The empty list in a function
declarator that is not part of a function definition specifies that no
information about the number or types of the parameters is supplied."
>
Almost identical wording appears in 6.7.5.3(14) of C99. Incidentally, the
wording is slightly tighter in C99 - which is actually quite interesting,
because it reveals a slight flaw in the wording of the above, but the
differences aren't relevant to the current case.

Yes, either "int main(void) { ... }" or "int main() { ... }" defines
main as taking no parameters; they're similar in that way. But one
similarity doesn't make them equivalent.

Here's what the standard says (C99 5.1.2.2.1):

The function called at program startup is named main. The
implementation declares no prototype for this function. It shall
be defined with a return type of int and with no parameters:

int main(void) { /* ... */ }

or with two parameters (referred to here as argc and argv, though
any names may be used, as they are local to the function in which
they are declared):

int main(int argc, char *argv[]) { /* ... */ }

or equivalent; or in some other implementation-defined manner.

The following two declarations:

int x;
double x;

are similar in that they both declare objects named "x". They're not
equivalent, though, because they declare objects of different types.
Even putting them in a program where the difference has no visible
effect doesn't make them equivalent; the programs might be effectively
equivalent, but the declarations aren't. (My argument here is just a
reasonable use of the word "equivalent ".)

The following two function definitions:

int main() { return 0; }
int main(void) { return 0; }

are similar in that they both declare and define a function called
"main". They differ in that, for example, one makes the call
"main(42)", appearing in another function in the same translation unit
following the above definition, invoke undefined behavior, while the
other makes it a constraint violation.

The standard doesn't say that the definition of main must be very
similar to "int main(void) { /* ... */ }", differing only in ways that
have no effect on the particular program being considered. It says
that it must be *equivalent* (or it must follow one of the other two
options).

In practice, most or all C compilers do support "int main()" with the
obvious semantics. If my interpretation is correct (and no, I'm not
100% certain of that), then "int main()", in an implementation that
doesn't document it, invokes undefined behavior; accept it is
perfectly legal.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"