problem with the code

[ramu]

Hi,
Is there any problem with the following code?

Regards

char *func()
{
char c;
return (&c);
}
#include<stdio. h>
int main()
{
char *ch;
ch = func();
*ch = 'A';
pritnf("%c",*ch );
}

[ramu]

Re: problem with the code

On Aug 25, 11:22 am, ramu <ramu....@gmail .comwrote:

Hi,
Is there any problem with the following code?
>
Regards
>
char *func()
{
char c;
return (&c);}
>
#include<stdio. h>
int main()
{
char *ch;
ch = func();
*ch = 'A';
pritnf("%c",*ch );
>
}

pritnf("%c",*ch );

>Sorry. It should be printf("%c", *ch);

[fjblurt@yahoo.com]

Re: problem with the code

On Aug 24, 11:22 pm, ramu <ramu....@gmail .comwrote:

Hi,
Is there any problem with the following code?
>
Regards
>
char *func()
{
char c;
return (&c);}
>
#include<stdio. h>
int main()
{
char *ch;
ch = func();
*ch = 'A';
pritnf("%c",*ch );
>
}

Looks like homework. How about if you explain whether *you* think
there's a problem, and why or why not. And don't forget, when you
submit the assignment, to acknowledge and cite as references the posts
of those who replied to you.

[Barry Schwarz]

Re: problem with the code

On Sun, 24 Aug 2008 23:22:01 -0700 (PDT), ramu <ramu.ask@gmail .com>
wrote:

>Hi,
Is there any problem with the following code?

Yes. It invokes undefined behavior.

>
>Regards
>
>char *func()
>{
char c;

c is an automatic variable. It comes into existence at the start of
this block of code.

return (&c);

And it goes out of existence when the function returns.

>}
>#include<stdio .h>
>int main()
>{
char *ch;
ch = func();

At this point ch receives the address of c which has just gone out of
existence. (By definition, the value in ch becomes indeterminate.)

*ch = 'A';

Here you attempt to store the value 'A' into an object that no longer
exists. (Technically, you are trying to evaluate an indeterminate
value which invokes undefined behavior.)

pritnf("%c",*ch );

This statement also invokes undefined behavior by trying to evaluate
the address in ch.

>}

--
Remove del for email

[Default User]

Re: problem with the code

ramu wrote:

Hi,
Is there any problem with the following code?
>
Regards
>
char *func()
{
char c;
return (&c);
}

This returns a pointer to a local variable. That variable goes out of
scope when the function returns. Any use of the pointer is undefined
behavior.



Brian

[jacob navia]

Re: problem with the code

Barry Schwarz wrote:

On Sun, 24 Aug 2008 23:22:01 -0700 (PDT), ramu <ramu.ask@gmail .com>
wrote:
>

>Hi,
> Is there any problem with the following code?

>
Yes. It invokes undefined behavior.
>

>Regards
>>
>char *func()
>{
> char c;

>
c is an automatic variable. It comes into existence at the start of
this block of code.
>

> return (&c);

>
And it goes out of existence when the function returns.
>

>}
>#include<stdio .h>
>int main()
>{
> char *ch;
> ch = func();

>
At this point ch receives the address of c which has just gone out of
existence. (By definition, the value in ch becomes indeterminate.)
>

> *ch = 'A';

>
Here you attempt to store the value 'A' into an object that no longer
exists. (Technically, you are trying to evaluate an indeterminate
value which invokes undefined behavior.)
>

> pritnf("%c",*ch );

>
This statement also invokes undefined behavior by trying to evaluate
the address in ch.
>

>}

>

FINE, now *you* did *his* homework.

Isn't clc great?


--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[jacob navia]

Re: problem with the code

Default User wrote:

ramu wrote:
>

>Hi,
> Is there any problem with the following code?
>>
>Regards
>>
>char *func()
>{
> char c;
> return (&c);
>}

>
This returns a pointer to a local variable. That variable goes out of
scope when the function returns. Any use of the pointer is undefined
behavior.
>
>
>
Brian

Why do you do his homework?

clc is there to get
(1): "off topic" remarks for most interesting posts, and
(2) Do the homework of lazy students.

--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[Richard Heathfield]

Re: problem with the code

ramu said:

Hi,
Is there any problem with the following code?
>
Regards
>
char *func()
{
char c;
return (&c);
}
#include<stdio. h>
int main()
{
char *ch;
ch = func();
*ch = 'A';
pritnf("%c",*ch );
}

Yes, there is a problem with that code (even assuming you meant printf
rather than pritnf).

Perhaps you could explain what you're trying to achieve? That would allow
us to suggest a good way to fix it.

--
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

[Richard]

Re: problem with the code

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

ramu said:
>

>Hi,
> Is there any problem with the following code?
>>
>Regards
>>
>char *func()
>{
> char c;
> return (&c);
>}
>#include<stdio .h>
>int main()
>{
> char *ch;
> ch = func();
> *ch = 'A';
> pritnf("%c",*ch );
>}

>
Yes, there is a problem with that code (even assuming you meant printf
rather than pritnf).
>
Perhaps you could explain what you're trying to achieve? That would allow
us to suggest a good way to fix it.

Why not tell him the returned address of c in func() us meaningless in
c.l.c land (it might be useful if you do not dereference it in some sort
of diagnostic tool)?

Why not tell him that printf() is possibly spelt wrong? Hey maybe he had
a function alled "pritnf" elsewhere?

And we wont even mention the main return code...

[raashid bhatt]

Re: problem with the code

On Aug 24, 11:22 pm, ramu <ramu....@gmail .comwrote:

Hi,
      Is there any problem with the following code?
>
Regards
>
char *func()
{
   char c;
   return (&c);}
>
#include<stdio. h>
int main()
{
   char *ch;
   ch = func();
   *ch = 'A';
    pritnf("%c",*ch );
>
}
>
>

as u see c is a local stack variable as soon a function returns the
its stack is cleared and it goes out of scope!

[Richard Heathfield]

Re: problem with the code

raashid bhatt said:

On Aug 24, 11:22 pm, ramu <ramu....@gmail .comwrote:

>Hi,
>Is there any problem with the following code?
>>
>Regards
>>
>char *func()
>{
>char c;
>return (&c);}
>>
>#include<stdio .h>
>int main()
>{
>char *ch;
>ch = func();
>*ch = 'A';
>pritnf("%c",*c h);
>>
>}

>
as u see c is a local stack variable as soon a function returns the
its stack is cleared and it goes out of scope!

Pretty much, yes. We can reduce the machine-specific nature of the reply by
re-wording to something like "c has automatic scope, and so it is
destroyed when control returns from func to its caller".

--
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

[jacob navia]

Re: problem with the code

Richard Heathfield wrote:

raashid bhatt said:
>

>On Aug 24, 11:22 pm, ramu <ramu....@gmail .comwrote:

>>Hi,
>>Is there any problem with the following code?
>>>
>>Regards
>>>
>>char *func()
>>{
>>char c;
>>return (&c);}
>>>
>>#include<stdi o.h>
>>int main()
>>{
>>char *ch;
>>ch = func();
>>*ch = 'A';
>>pritnf("%c",* ch);
>>>
>>}

>as u see c is a local stack variable as soon a function returns the
>its stack is cleared and it goes out of scope!

>
Pretty much, yes. We can reduce the machine-specific nature of the reply by
re-wording to something like "c has automatic scope, and so it is
destroyed when control returns from func to its caller".
>

I just can't understand why everybody competes in the
game:

Who does better ramu's homework?

You are NOT helping him.

--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[pete]

Re: problem with the code

Richard Heathfield wrote:

raashid bhatt said:
>

>On Aug 24, 11:22 pm, ramu <ramu....@gmail .comwrote:

>>Hi,
>>Is there any problem with the following code?
>>>
>>Regards
>>>
>>char *func()
>>{
>>char c;
>>return (&c);}
>>>
>>#include<stdi o.h>
>>int main()
>>{
>>char *ch;
>>ch = func();
>>*ch = 'A';
>>pritnf("%c",* ch);
>>>
>>}

>as u see c is a local stack variable as soon a function returns the
>its stack is cleared and it goes out of scope!

>
Pretty much, yes. We can reduce the machine-specific nature of the reply by
re-wording to something like "c has automatic scope, and so it is
destroyed when control returns from func to its caller".
>

ITYM "automatic duration"

--
pete

[Richard Heathfield]

Re: problem with the code

pete said:

Richard Heathfield wrote:

<snip>

>Pretty much, yes. We can reduce the machine-specific nature of the reply
>by re-wording to something like "c has automatic scope, and so it is
>destroyed when control returns from func to its caller".
>>

>
ITYM "automatic duration"

SDI. TY.

--
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

[Richard Heathfield]

Re: problem with the code

jacob navia said:

<snip>

I just can't understand why everybody competes in the
game:
>
Who does better ramu's homework?
>
You are NOT helping him.

Once the cat is out of the bag (which it was, by the time of my second
reply), we might as well make sure that it's the right cat.

--
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