Is the behaviour defined

[grid]

Hi,
A collegue of mine is of the opinion that the behaviour of the
following program is defined,but I am a little apprehensive.

#include<stdio. h>
#include<string .h>

int main()
{
char *c;
c = &c;
strcpy(c,"abc") ;
puts(&c);
retun 0;
}

The program prints the same value "abc" on multiple platforms and I even
tried it with multiple compilers.I can make out that its trying to write
to the pointer address and so probably the max it can write is 3 bytes +
'\0'.But even if I try to copy more that 4 bytes it prints the whole
string without any crashes.

Changed line >> strcpy(c,"abcde fg");

Now I know that this behaviour is undefined(writi ng more than 4 bytes)
as the sizeof the pointer is 4 bytes(on the machine I tested on).

Can anyone comment if this is compliant code and is the behaviour
guaranteed.

Thanks
~

[pete]

Marc Boyer wrote:

Here is a well defined program:

#include <stdio.h>
#include <string.h>

int main(){
void* p= &p;
if ( strlen("abc") < sizeof(p) ){
memcpy(p, "abc", strlen("abc")+1 );
puts( (char*) p );

It's not defined and these issues have
already been gone over in this thread.

p is an indeterminate pointer after the memcpy call.

Accessing the value of p at that point,
as the cast operator does, is undefined.

#include <stdio.h>
#include <string.h>

#include <stdio.h>
#include <string.h>

int main(void)
{
void *p = &p;

if (strlen("abc") < sizeof(p)) {
strcpy(p, "abc");
puts((char *)&p);
} else {
puts("Pointers too small");
}
return 0;
}

--
pete

[Marc Boyer]

Le 07-10-2005, pete <pf*****@mindsp ring.com> a écrit*:

Marc Boyer wrote:

Here is a well defined program:

#include <stdio.h>
#include <string.h>

int main(){
void* p= &p;
if ( strlen("abc") < sizeof(p) ){
memcpy(p, "abc", strlen("abc")+1 );
puts( (char*) p );
It's not defined and these issues have
already been gone over in this thread.

p is an indeterminate pointer after the memcpy call.

Yes, sorry. I ve not posted the right version.
Accessing the value of p at that point,
as the cast operator does, is undefined.
Of course.
#include <stdio.h>
#include <string.h>

#include <stdio.h>
#include <string.h>

int main(void)
{
void *p = &p;

if (strlen("abc") < sizeof(p)) {
strcpy(p, "abc");
puts((char *)&p);
} else {
puts("Pointers too small");
}
return 0;
}

Yes
--
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