printing values of "arrays of pointers"

[arnuld]

PURPOSE: see the comments.
WHAT I GOT: infinite loop

/* This program will simply create an array of pointers to integers
* and will fill it with some values while using malloc to create
* pointers to fill the array and then will print the values pointed
* by those pointers
*
*/

#include <stdio.h>
#include <stdlib.h>

enum MAXSIZE { ARRSIZE = 100 };
int main( void )
{
int* arr_p[ARRSIZE];
int** pp;
int *mp, *np;
int i;

int null_int = 0;

pp = arr_p;
np = &null_int;
for( i = 0; i < ARRSIZE - 1; ++i )
{
mp = malloc( sizeof( int ) );
mp = &i;
arr_p[i] = mp;
}
arr_p[i] = np;

while( **pp )
{
printf("**pp = %d\n", **pp);
}

return 0;
}

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my email ID is @ the above address

[arnuld]

On Sat, 03 May 2008 16:21:35 +0530, santosh wrote:

More practically Sunsite could terminate his account with them if they
were to be alerted to his behaviour. Their rules clearly say that users
are only to use their own email addresses which actually exist and can
be delivered to, in the Sender field.

If I use my real email ID that means I am inviting 100% of spam. I don't
want to be spammed and no one wants to be spammed.

Regarding microsoft.com, I got that idea from my friend. He told me that
when he is using Outlook Express on WindowsXP, he gets this:
....@microsoft. com, as default address.

--
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my email ID is @ the above address

[arnuld]

On Sat, 03 May 2008 16:21:35 +0530, santosh wrote:

More practically Sunsite could terminate his account with them if they
were to be alerted to his behaviour. Their rules clearly say that users
are only to use their own email addresses which actually exist and can
be delivered to, in the Sender field.

I think this Server Policy is good:

http://news.aioe.org/spip.php?article3

--
http://lispmachine.wordpress.com/
my email ID is @ the above address

[arnuld]

On Sat, 03 May 2008 16:21:35 +0530, santosh wrote:

More practically Sunsite could terminate his account with them if they
were to be alerted to his behaviour. Their rules clearly say that users
are only to use their own email addresses which actually exist and can
be delivered to, in the Sender field.

I have mailed them and have asked them to change their policy.

--
http://lispmachine.wordpress.com/
my email ID is @ the above address

[Richard Heathfield]

arnuld said:

>On Sat, 03 May 2008 16:21:35 +0530, santosh wrote:

>More practically Sunsite could terminate his account with them if they
were to be alerted to his behaviour. Their rules clearly say that users
are only to use their own email addresses which actually exist and can
be delivered to, in the Sender field.

If I use my real email ID that means I am inviting 100% of spam. I don't
want to be spammed and no one wants to be spammed.

Nobody wants to be spammed. On the other hand, how would you like it if
someone used *your* real address in *their* From field?

All you have to do is invent an address that is in the correct form but
guaranteed not to exist. For example, sp**@spam.invalid is a well-formed
email address that definitely doesn't exist (because there is no top-level
domain called "invalid"). This is not an area where originality is
terribly important. If in doubt, use sp**@spam.invalid for From and
Reply-To, and mung your real email address in your sig block.

--
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

[arnuld]

On Mon, 05 May 2008 04:48:11 +0000, Richard Heathfield wrote:

Nobody wants to be spammed. On the other hand, how would you like it if
someone used *your* real address in *their* From field?

:(

All you have to do is invent an address that is in the correct form but
guaranteed not to exist. For example, sp**@spam.invalid is a well-formed
email address that definitely doesn't exist (because there is no top-level
domain called "invalid"). This is not an area where originality is
terribly important. If in doubt, use sp**@spam.invalid for From and
Reply-To, and mung your real email address in your sig block.

how about my present address ? It doe not use any real domain name and is
different enough from common words like spam, invalid, nospam etc.

BTW, I don't see Reply-To header for my own posts, not even for the posts
of BartC and santosh but I do see Reply-To header of yours. ( I have
already enabled all headers in PAN preferences)

--
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my email ID is @ the above blog.
just check the "About Myself" page :)

[CBFalconer]

arnuld wrote:

>Richard Heathfield wrote:

.... snip ...

>

>All you have to do is invent an address that is in the correct
form but guaranteed not to exist. For example, sp**@spam.invalid
is a well-formed email address that definitely doesn't exist
(because there is no top-level domain called "invalid"). This is
not an area where originality is terribly important. If in doubt,
use sp**@spam.invalid for From and Reply-To, and mung your real
email address in your sig block.

how about my present address ? It doe not use any real domain
name and is different enough from common words like spam, invalid,
nospam etc.

No. People can create new domains and addresses at any time. The
..invalid domain is guaranteed not to exist, and thus to never cause
problems.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
** Posted from http://www.teranews.com **

[arnuld]

On Mon, 05 May 2008 02:25:53 -0400, CBFalconer wrote:

No. People can create new domains and addresses at any time. The
.invalid domain is guaranteed not to exist, and thus to never cause
problems.

so "invalid" is the only one that is usable :(

--
http://lispmachine.wordpress.com/
my email ID is @ the above blog.
just check the "About Myself" page :)

[Keith Thompson]

arnuld <su*****@domain .tldwrites:

>On Mon, 05 May 2008 02:25:53 -0400, CBFalconer wrote:
No. People can create new domains and addresses at any time. The
.invalid domain is guaranteed not to exist, and thus to never cause
problems.

so "invalid" is the only one that is usable :(

<OT>
No, it's not the only one, but it's the most appropriate for your
purposes. Point your web browser to <http://example.com/and follow
the link for more information.

But even if it were the only one, why would that be a problem? How
many invalid TLDs do you need? (Hint: the correct answer is an
integer between 0 and 2.)

If you want to discuss this further, please find a newsgroup or other
forum where it's topical.
</OT>

--
Keith Thompson (The_Other_Keit h) <ks***@mib.or g>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Nick Keighley]

On 2 May, 14:44, Richard Heathfield <[e-mail].i nvalidwrote:

arnuld said:

PURPOSE: * * * * see the comments.
WHAT I GOT: * * *infinite loop

/* This program will simply create an array of pointers to integers
** and will fill it with some values while using malloc to create
** pointers to fill the array and then will print the values pointed
** by those pointers
**
**/

#include <stdio.h>
#include <stdlib.h>

enum MAXSIZE { ARRSIZE = 100 };

int main( void )
{
* int* arr_p[ARRSIZE];
* int** pp;
* int *mp, *np;
* int i;

* int null_int = 0;

* pp = arr_p;
* np = &null_int;

* for( i = 0; i < ARRSIZE - 1; ++i )
* * {
* * * mp = malloc( sizeof( int ) );

You don't check to see whether this fails to allocate the requested
memory...

* * * mp = &i;

...which doesn't really matter, since you throw it away here.

* * * arr_p[i] = mp;
* * }

Well done. You just filled arr_p with a bunch of pointers to i. Why
bother with the malloc call, then? You could save yourself
(ARRSIZE-1) * sizeof(int) bytes of memory leak by removing the malloc call completely.

* arr_p[i] = np;

* while( **pp )

pp has the value &arr_p[0], so **pp attempts to find the int value at
*arr_p[0]. Since arr_p[0] points to i, we're looking for the value of i.
That value is indeterminate, because the object i never had a value
assigned to it.

not even in the for loop?

Thus, the behaviour is undefined. This loop could execute
forever (the most likely possibility) or not at all (probably the
second most likely) or something completely weird could happen.

* * {
* * * printf("**pp = %d\n", **pp);

if you want to print a pointer (and **pp *isn't a pointer)
use %p. Instead of trying to be clever why not use a for loop?

for (i = 0; i < ARRSIZE; i++)
printf ("%p ", (void*)arr_p[i]);

printf ("\n");

* * }

You don't even /try/ to iterate through the array, do you? You might
want
to take a long hard look at Visual Basic or RCX.

--
Nick Keighley

My god it's full of stars!
Dave Bowman, on seeing HAL's source code

[Nick Keighley]

On 2 May, 15:05, arnuld <NoS...@microso ft.comwrote:

On Fri, 02 May 2008 13:44:50 +0000, Richard Heathfield wrote:

* for( i = 0; i < ARRSIZE - 1; ++i )
* * {
* * * mp = malloc( sizeof( int ) );

You don't check to see whether this fails to allocate the requested
memory...

done

* * * mp = &i;

...which doesn't really matter, since you throw it away here.

well, then how can I generate a new variable every-time I enter into
the loop ?

you can't. Well you can but you don't want to.

for( i = 0; i < ARRSIZE - 1; ++i )
{
int new;
arr_p[i] = &new;
}

The Standard doesn't say if new has the same address every time,
but on almost any reasonable implementation it does. Hence you
don't want to do this.

So why not malloc an object and store its address in the array?
You probably meant to do that but your code really didn't
do that.

for( i = 0; i < ARRSIZE - 1; ++i )
{
if ((mp = malloc (sizeof (int))) == NULL)
{
fprintf (stderr, "memory error\n");
abort();
}

arr_p[i] = mp;
}
<snip>

--
Nick Keighley

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This option is not intended to be useful; it exists only to satisfy
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