Re: OT: Language War (Re: "C" Manual)

[dman <dsh8290@rit.edu>]

On Thu, Jan 03, 2002 at 12:19:25AM -0500, William T Wilson wrote:
| On Wed, 2 Jan 2002, Richard Cobbe wrote:
| 
| > I'll agree that the two are related; in fact, I'd go so far as to say
| > that if a language supports dynamic memory allocation and type-safety,
| > it *has* to have some sort of automatic storage management system.
| 
| I don't think that necessarily follows; a manual mechanism for freeing
| resources would then just set the reference to a NULL value.

Erm, no.  The function can't change the environment of its caller :

int main()
{
    int* ptr ;

    /* allocate some space */
    ptr = malloc( 2*sizeof(int) ) ;
    /* see where that space starts */
    printf( "%d" , ptr ) ;
    free( ptr ) ;
    /* it still points there, but dereferencing the pointer now is bad */
    printf( "%d" , ptr ) ;
    return 1 ;
}


If you wrote a wrapper around free() that took a pointer to a pointer
you _could_ then assign NULL to the second pointer, but that, of
course, assumes that inside free() you have a valid pointer to
dereference in the first place.

-D

-- 

Trust in the Lord with all your heart and lean not on your own
understanding; in all your ways acknowledge Him, and He will make your
paths straight.
        Proverbs 3:5-6