Re: OT: Possible memory leak in an exercise of a C handbook

[Franco Martelli <martellif67@gmail.com>]

On 16/12/24 at 20:42, Michael Kjörling wrote:
> On 16 Dec 2024 17:21 +0100, from martellif67@gmail.com (Franco Martelli):
> > > Put in something to count the number of calls to malloc() and free()
> > > respectively. Don't forget calls outside of loops.
> >
> > There isn't calls to malloc() or free() outside loops. What do you mean?
>
> > From a quick re-glance through your code...
>
>          if ( head == NULL )
>          {
> ==>             head = last = (DIGIT *) malloc( sizeof ( DIGIT ) );
>                  head->dgt = last->dgt = i;
>                  head->next = head->prev = last->next = last->prev = NULL;
>                  return;
>          }
>          /* Otherwise, find the last element in the list */
>          for (p = head; p->next != NULL; p = p->next)
>                  ; /* null statement */
>
> ==>     p->next = (DIGIT *) malloc( sizeof ( DIGIT ) );

Yes, but those calls in add_element(int) happen because add_element(int) 
is called only by the "for loop" in main().
I realized what you suggest after reply to your email: place a 
printf("+") after every malloc(…) call and place a printf("-") after 
every free() call.

> and
>
>          for ( const DIGIT *p = head; p->next != NULL; p = p->next )
>                  if ( p->prev != NULL )
>                          free( p->prev );
> ==>     free( last );
>
> certainly look to me like they're outside of loops.
Yes, that call is outside the loop, but I realized after reply to your 
email of your suggestion.
Thank you very much for the tips!

--
Franco Martelli