why malloc() return different pointer value?
 

Such a program:

#include <stdio.h>
main()
{
void* p;
p=malloc(16);
printf("%p\n",p);
}

Compiled on linux then run it. The result will different for every times and the difference may be some pages.

On other unix system, such as solaris or HP-UX, the result for every running are same.

I think that unix process would have same mermory space mechanism, but why I got this result on linux??

Thanks for any help.

malloc () makes absolutely no guarantee that you'll get the same address each time. Maybe on some systems you will often get the same value, but I very much doubt that this is guaranteed. In general, you shouldn't actually be examining the return value from malloc () (all you need to know is that you've got a memory location to use, you shouldn't care where it is), except to check that it isn't NULL.