free (p)

[nicolas]

When you declare a *p, assign memory to it

p = (char*)malloc(5*sizeof(char));

and then release it

free (p);

it´s recommended to do the following:

p = NULL;

right?

If this is recommended then why doesn´t the "free" function already includes this assignment inside?

Thanks.

[Thantos]

Because there is no requirement to do so.

If you want you can make your own:

void *myfree(void *ptr)
{
  free(ptr);
  return NULL;
}

[Salem]

> If this is recommended then why doesn´t the "free" function already includes this assignment inside?
Because pointers (like everything else) are passed by value

void myfree ( void *ptr ) {
   free( ptr );
   ptr = NULL;
}


int main ( ) {
    char *p = malloc( 10 );
    myfree( p );
    /* p won't be NULL here, but it will have been freed */
}

If you want a myfree which does reset the pointer, then you need to do this

void myfree ( void **ptr ) {
   free( *ptr );
   *ptr = NULL;
}


int main ( ) {
    char *p = malloc( 10 );
    myfree( &p );
}