resolved: difference between memcpy and memmove

[Mac]

$ cat junk27.c
#include <stdio.h>
#include <string.h>

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);
return 0;
}

$ make junk27
cc -Wall -ansi -pedantic junk27.c -o junk27

$ ./junk27
The difference between memcpy and memmove is 48
$
So now we can put that behind us.

Mac
--

[Mike Wahler]

"Mac" <fo*@bar.net> wrote in message
news:pa******** *************** *****@bar.net.. .

$ cat junk27.c
#include <stdio.h>
#include <string.h>
You don't need this header.

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);
Note: This is not portable. But if I wanted to do this,
I'd use 'unsigned long' or 'unsigned long long'.

6.3.2.3 Pointers

6 Any pointer type may be converted to an integer type.
Except as previously specified, the result is implementation-
defined. If the result cannot be represented in the integer type,
the behavior is undefined. The result need not be in the range
of values of any integer type.

AFAICT, 'previously specified' only refers to:

6.3.2.3

3 An integer constant expression with the value 0, or such
an expression cast to type void *, is called a null pointer
constant. If a null pointer constant is converted to a
pointer type, the resulting pointer, called a null pointer,
is guaranteed to compare unequal to a pointer to any object
or function.
return 0;
}

-Mike

[Bertrand Mollinier Toublet]

Mike Wahler wrote:

"Mac" <fo*@bar.net> wrote in message
news:pa******** *************** *****@bar.net.. .

$ cat junk27.c
#include <stdio.h>
#include <string.h>
You don't need this header.

Are you so sure ? Seems to me that without it, memcpy and memmove are
undeclared identifiers...

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);

--
Bertrand Mollinier Toublet
Blog: http://www.bmt.dnsalias.org/blog

[Richard Heathfield]

Mac wrote:

$ cat junk27.c
#include <stdio.h>
#include <string.h>

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);
return 0;
}

That's the first comp.lang.c article to make me GLOL for quite a while.

(Where has all the humour gone?)

--
Richard Heathfield : bi****@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

[Mike Wahler]

"Bertrand Mollinier Toublet"
<be************ *************** **@enst-bretagne.fr> wrote in message
news:bl******** ****@ID-168218.news.uni-berlin.de...

Mike Wahler wrote:

"Mac" <fo*@bar.net> wrote in message
news:pa******** *************** *****@bar.net.. .

$ cat junk27.c
#include <stdio.h>
#include <string.h>

You don't need this header.

Are you so sure ? Seems to me that without it, memcpy and memmove are
undeclared identifiers...

You are now authorized to beat me over the head
with an undeclared identifier until my behavior
becomes well-defined. :-)

-Mike

[Irrwahn Grausewitz]

"Mac" <fo*@bar.net> wrote:

$ cat junk27.c
#include <stdio.h>
#include <string.h>

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);
return 0;
}

$ make junk27
cc -Wall -ansi -pedantic junk27.c -o junk27

$ ./junk27
The difference between memcpy and memmove is 48
$

*LOL*

Well, it's 16 on my implementation, which is one third of your result.
Does this mean the relation between memcpy and memmove is three times
closer on my system?

Irrwahn
--
Computer: a million morons working at the speed of light.

[Irrwahn Grausewitz]

Richard Heathfield <do******@addre ss.co.uk.invali d> wrote:

(Where has all the humour gone?)

The what?
--
Computer: a million morons working at the speed of light.

[Mike Wahler]

"Irrwahn Grausewitz" <ir************ *****@freenet.d e> wrote in message
news:o2******** *************** *********@4ax.c om...

"Mac" <fo*@bar.net> wrote:

$ cat junk27.c
#include <stdio.h>
#include <string.h>

int main (void)
{
printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);
return 0;
}

$ make junk27
cc -Wall -ansi -pedantic junk27.c -o junk27

$ ./junk27
The difference between memcpy and memmove is 48
$

*LOL*

Well, it's 16 on my implementation, which is one third of your result.
Does this mean the relation between memcpy and memmove is three times
closer on my system?

If the relation is expressed in distance using
memory addresses, then it's 66.67% closer.

-Mike

[Arthur J. O'Dwyer]

On Sat, 27 Sep 2003, Mike Wahler wrote:

"Irrwahn Grausewitz" <ir************ *****@freenet.d e> wrote in message
news:o2******** *************** *********@4ax.c om...

"Mac" <fo*@bar.net> wrote:

$ ./junk27
The difference between memcpy and memmove is 48

*LOL*
Well, it's 16 on my implementation, which is one third of your result.
Does this mean the relation between memcpy and memmove is three times
closer on my system?

If the relation is expressed in distance using
memory addresses, then it's 66.67% closer.

No, it's 66.67% *less far*. It's still three times *closer*,
using the traditional metric

closity = 1.0 / farthitude

:-)

-Arthur

[Ben Pfaff]

"Mike Wahler" <mk******@mkwah ler.net> writes:

printf("The difference between memcpy and memmove is %ld\n",
(long int) memcpy - (long int) memmove);

Note: This is not portable. But if I wanted to do this,
I'd use 'unsigned long' or 'unsigned long long'.

For what it's worth, C99 has intptr_t and uintptr_t in
<stdint.h>. But they are optional and don't apply to function
pointers anyway.
--
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan